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Pirc Defence

The Pirc Defence is a chess opening characterised by the response of Black to 1.e4 with 1...d6 and 2...Nf6, followed by ...g6 and ...Bg7, while allowing White to establish a  with pawns on d4 and e4. It is named after the Slovenian grandmaster Vasja Pirc.

The Pirc Defence is usually defined by the opening sequence
 * 1. e4 d6
 * 2. d4 Nf6
 * 3. Nc3 g6

This is the most commonly played line after Black responds to 1.e4 with 1...d6. It has been claimed to give rise to somewhat interesting and exciting games, where Black will have but has to be cautious about playing too passively. According to Garry Kasparov, the Pirc Defence is "hardly worth using in the tournaments of the highest category", as it gives White "too many opportunities for anybody's liking".

Description
The Pirc Defence, named after Slovenian grandmaster Vasja Pirc, is a relatively new opening; while it was seen on occasion in the late nineteenth century, it was considered irregular, thus remaining a sideline. The opening began gaining some popularity only after World War II, and by the 1960s it was regarded as, owing in large part to the efforts of Canadian grandmaster Duncan Suttles. Black, in hypermodern fashion, does not immediately stake a claim in the centre with pawns; rather, Black works to undermine White's centre from the. Its first appearance in a World Championship match was in 1972, when it was played by Bobby Fischer against Boris Spassky at Reykjavík (game 17); the game ended in a draw.

Hooper and Whyld gave a distinct formal definition, 1.d4 d6 2.e4 Nf6 3.Nc3 g6, permuting White's first two moves, although they qualified the definition by remarking that 1.e4 d6 could also transpose to the Pirc. The presence or absence of Black's third move in the Pirc is reported differently, according to the source; with the pawn move 3...g6, Black prepares to fianchetto the king's bishop to g7. Paul van der Sterren therefore described 3...g6 as "the defining move of the Pirc Defence" because the development of the bishop to g7 "creates the same sort of positional tension as the King's Indian Defence".

A distinction is usually drawn between the Pirc and lines where Black delays the development of his knight to f6, or omits it altogether; this is known as the Modern or Robatsch Defence. The tenth edition of Modern Chess Openings (1965) grouped the Pirc and Robatsch together as the "Pirc–Robatsch Defense".

Austrian Attack: 4.f4
The Austrian Attack begins 1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.f4 Bg7 5.Nf3, and was a favourite of Fischer. It is also well respected by Nick de Firmian, the author of Modern Chess Openings. In placing pawns on d4, e4 and f4, White establishes a powerful centre, intending to push in the centre and/or attack on the ; in the main line, Black will usually counter with ...e5, aiming for play against the dark squares and weaknesses created by White's central advance. This direct, aggressive line is one of the most ambitious systems against the Pirc. Jan Timman has played the Austrian successfully with both colours. Yuri Balashov does well with the white pieces, and Valery Beim has an impressive score on the black side.

5...0-0
The most frequently played move after 5...0-0 is 6.Bd3 (the Weiss Variation), with 6...Nc6 the most common response, though 6....Na6, with the idea of ....Nc7, ....Rb8 and ....b5 became popular in the 1980s after 6....Nc6 was found to offer Black few winning chances. 6.e5 is a try, with unclear consequences, which was much played in the 1960s, though it has never attained popularity at the highest levels. 6.Be2 is another move which was often seen in the 1950s and early 1960s, although the defeat sustained by Fischer in the game given in the example games spurred White players, including Fischer, to turn to 6.Bd3. In the 1980s, 6.Be2 c5 7.dxc5 Qa5 8.0-0 Qxc5+ 9.Kh1 was revived with more favourable results. 6.Be3 is another possibility, first extensively explored in the 1970s and played by Bojan Kurajica, Yuri Balashov and Alexander Beliavsky, which leads to sharp play.

5...c5
Black's chief alternative to 5...0-0 lies in an immediate strike against the white centre with 5...c5, to which the usual response is either 6.dxc5 or 6.Bb5+. The former allows 6...Qa5. The latter promises a tactical melee, with a common line being 6.Bb5+ Bd7 7.e5 Ng4 8.e6 (8.h3 or 8.Bxd7+ are other possibilities) 8...fxe6, which was thought bad, until Yasser Seirawan played the move against Gyula Sax in 1988 (8...Bxb5 is the alternative, if Black does not want the forced draw in the main line), continuing 9.Ng5 Bxb5 Now if White tries 10.Nxe6, Black has 10...Bxd4!, ignoring the threat to his queen, in view of 11.Nxd8 Bf2+ 12.Kd2 Be3+ with a draw by perpetual check. White can instead try 11.Nxb5, with complicated play.

White can also essay the sharp 6.e5 against 5...c5, after which 6...Nfd7 7.exd6 0-0 is considered to offer good play for Black.

Classical (Two Knights) System: 4.Nf3
The Classical (Two Knights) System begins 1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Nf3 Bg7 5.Be2 0-0 6.0-0. White contents themselves with the 'classical' with pawns at e4 and d4, forgoing the committal move f2–f4 as Black castles and builds a compact structure. Efim Geller, Anatoly Karpov and Evgeni Vasiukov have all successfully used this system for White; Zurab Azmaiparashvili has scored well as Black. This transposes into the Sicilian Dragon after 6...c5 7.Be3 cxd4 8.Nxd4.

The 150 and Argentine Attacks
The setup f2–f3, Be3 and Qd2 is commonly used against the King's Indian Defence and Dragon Sicilian, and can also be used against the Pirc; indeed, this system is as old as the Pirc itself.

The system 4.f3 was introduced by Argentine players c. 1930 and again in 1950. It was never considered dangerous for Black because of 4.f3 Bg7 5.Be3 c6 6.Qd2 b5. It received a severe blow in about 1985, when Gennady Zaichik showed that Black could castle anyway and play a dangerous gambit with 5...0-0 6.Qd2 e5.

The Argentines feared the sally ...Ng4, though some British players (especially Mark Hebden, Paul Motwani, Gary Lane, later also Michael Adams) came to realise that this was mainly dangerous for Black, therefore playing Be3 and Qd2 in all sorts of move orders, while omitting f2–f3. They called this the 150 Attack, because players of this strength (150 ECF) can easily play this position and get strong play without any theory.

The original Argentine idea probably is only viable after 4.Be3 Bg7 5.Qd2 0-0 6.0-0-0 c6 (or Nc6) 7.f3 b5 8.h4. Black usually does not castle, though, and prefers 5...c6 or even 4...c6. The question of whether and when to insert Nf3 remains unclear.

Other systems

 * 4.Bg5 was introduced by Robert Byrne in the 1960s, after which Black has often played the natural 4...Bg7, though 4...c6 is considered more flexible, as Black may wish to save a tempo in anticipation of White's plan of Qd2, followed by Bh6, by deferring ...Bg7 as long as possible, playing for activity with ...b7–b5 and ...Qa5. White's idea of Qd2 and Bh6 may give a transposition to the lines with Be3 and Qd2. A less common method of playing this system is 4.Nf3 Bg7 5.Bg5.
 * 4.Bf4. This formerly rare move has become more popular lately, in large part because the position can come about via a fashionable line of the London System: 1.d4 Nf6 2.Bf4 g6 3.Nc3 d6 4.e4.
 * 4.Bc4 Bg7 5.Qe2 is a sharp try for advantage; 5...Nc6 can lead to hair-raising complications after 6.e5, when Black's best line may be 6...Ng4 7.e6 Nxd4 8.Qxg4 Nxc2+, avoiding the more frequently played 6...Nxd4 7.exf6 Nxe2 8.fxg7 Rg8 9.Ngxe2 Rxg7, which has been generally considered to lead to an equal or unclear position, though White has scored heavily in practice. 6...Nd7 is now considered fine for Black, in view of 7.e6 fxe6 8.Qxe6 Nde5! 9.Qd5 e6 with advantage to Black. If White instead plays the better 7.Nf3, Black has multiple choices, including 7...0-0 and 7...Nb6 (followed by ...Na5), which is considered to equalise. Another possibility for Black is 5...c6, though 6.e5 dxe5 7.dxe5 Nd5 8.Bd2, followed by long castling, gives White the advantage, as Black's position is cramped and he lacks active counterplay.
 * 4.g3 and 5.Bg2, followed by Nge2, is a solid line, which was sometimes adopted by Karpov.
 * 4.Be3 is another alternative. Considered relatively passive in earlier times, today's practice uses this move as a flexible entry into lines which may feature h3/Nf3 or even h3/g4/Bg2 – while still maintaining the option of returning to 150-like plans or the Austrian if Black commits to moves that do not help in this type of position.
 * 4.Be2 may transpose into the Classical System after 4...Bg7 5.Nf3, or White may try one of two highly aggressive lines, the Bayonet Attack (5.h4) or the Chinese Variation (5.g4).

Early deviations
After 1.e4 d6 2.d4 Nf6 3.Nc3, Black has an alternative to 3...g6 (Main line) known as the Pribyl System or Czech Defence, beginning 3...c6. The lines often transpose to the Pirc if Black later plays ...g6; alternatively, Black can play ...Qa5 and ...e5 to challenge White's centre, or expand on the with ...b5.

A common deviation by Black in recent practice is 1.e4 d6 2.d4 Nf6 3.Nc3 e5. This has been tried by many GMs over the years, including Zurab Azmaiparashvili and Christian Bauer. White's 4.dxe5 is known to be equal, and play normally continues 4...dxe5 5.Qxd8+ Kxd8 6.Bc4 Be6 7.Bxe6 fxe6. Instead, White normally transposes to the Philidor Defence with 4.Nf3.

An unusual deviation for Black is 1.e4 d6 2.d4 Nf6 3.Nc3 e6, which can transpose to the Scheveningen Variation of the Sicilian Defence after 4.Nf3 Be7 5.Bb5+ c6 6.Be2 0-0 7.Be3 c5 8.0-0 cxd4 9.Nxd4.

An unusual but quite reasonable deviation for White is 1.e4 d6 2.d4 Nf6 3.f3. At the 1989 Barcelona World Cup event, former world champion Garry Kasparov surprised American grandmaster Yasser Seirawan with this move. After 3...g6 4.c4, an unhappy Seirawan found himself defending the King's Indian Defence for the first time in his life, though he managed to draw the game. Black can avoid a King's Indian with 3...e5, which may lead to an Old Indian type of position after 4.d5, with 3...c5, which may lead to a Benoni type of position after 4.d5 or transpose to Prins Variation of the Sicilian Defence after 4.Ne2 cxd4 5.Nxd4, or with 3...d5. This can transpose to the Classical Variation of the French Defence after 4.e5 Nfd7 5.f4 e6 6.Nf3, to the Tarrasch Variation of the French Defence after 4.e5 Nfd7 5.f4 e6 6.c3 c5 7.Nd2 Nc6 8.Ndf3, or even to the Blackmar–Diemer Gambit with an extra tempo for White after 4.Nc3 dxe4 5.Bg5 exf3 6.Nxf3.

Example games
1.e4 d6 2.d4 g6 3.Nf3 Nf6 4.Nc3 Bg7 5.Be2 0-0 6.0-0 Bg4 7.Be3 Nc6 8.Qd2 e5 9.d5 Ne7 10.Rad1 b5 11.a3 a5 12.b4 axb4 13.axb4 Ra3 14.Bg5 Rxc3 15.Bxf6 Bxf3 16.Bxf3 Ra3 17.Bxg7 Kxg7 18.Ra1 Qa8 19.Rxa3 Qxa3 20.Be2 Qb2 21.Rd1 f5 22.exf5 Nxf5 23.c3 Qxd2 24.Rxd2 Ra8 25.Bxb5 Ra3 26.Rc2 Ne7 27.f4 exf4 28.Bc6 Nf5 29.Kf2 Ne3 30.Rc1 Kf6 31.g3 Ke5 32.Kf3 g5 33.gxf4+ gxf4 34.h4 Nxd5 35.Bxd5 Kxd5 36.Kxf4 Kc4 37.Re1 Rxc3 38.Re7 Kxb4 39.Rxh7 d5 40.Ke5 c6 41.Kd4 Rc4+ 1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.Be3 Bg7 5.Qd2 c6 6.f3 b5 7.Nge2 Nbd7 8.Bh6 Bxh6 9.Qxh6 Bb7 10.a3 e5 11.0-0-0 Qe7 12.Kb1 a6 13.Nc1 0-0-0 14.Nb3 exd4 15.Rxd4 c5 16.Rd1 Nb6 17.g3 Kb8 18.Na5 Ba8 19.Bh3 d5 20.Qf4+ Ka7 21.Rhe1 d4 22.Nd5 Nbxd5 23.exd5 Qd6 24.Rxd4 cxd4 25.Re7+ Kb6 26.Qxd4+ Kxa5 27.b4+ Ka4 28.Qc3 Qxd5 29.Ra7 Bb7 30.Rxb7 Qc4 31.Qxf6 Kxa3 32.Qxa6+ Kxb4 33.c3+ Kxc3 34.Qa1+ Kd2 35.Qb2+ Kd1 36.Bf1 Rd2 37.Rd7 Rxd7 38.Bxc4 bxc4 39.Qxh8 Rd3 40.Qa8 c3 41.Qa4+ Ke1 42.f4 f5 43.Kc1 Rd2 44.Qa7 1.Nf3 g6 2.e4 Bg7 3.d4 d6 4.Nc3 Nf6 5.Be2 0-0 6.0-0 Nc6 7.d5 Nb8 8.Re1 e5 9.dxe6 Bxe6 10.Bf4 h6 11.Nd4 Bd7 12.Qd2 Kh7 13.e5 dxe5 14.Bxe5 Ne4 15.Nxe4 Bxe5 16.Nf3 Bg7 17.Rad1 Qc8 18.Bc4 Be8 19.Neg5+ hxg5 20.Nxg5+ Kg8 21.Qf4 Nd7 22.Rxd7 Bxd7 23.Bxf7+ 1–0 1.e4 d6 2.d4 Nf6 3.Nc3 g6 4.f4 Bg7 5.Nf3 0-0 6.Be2 c5 7.dxc5 Qa5 8.0-0 Qxc5+ 9.Kh1 Nc6 10.Nd2 a5 11.Nb3 Qb6 12.a4 Nb4 13.g4 Bxg4! 14.Bxg4 Nxg4 15.Qxg4 Nxc2 16.Nb5 Nxa1 17.Nxa1 Qc6 18.f5 Qc4 19.Qf3 Qxa4 20.Nc7 Qxa1 21.Nd5 Rae8 22.Bg5 Qxb2 23.Bxe7 Be5 24.Rf2 Qc1+ 25.Rf1 Qh6 26.h3 gxf5 27.Bxf8 Rxf8 28.Ne7+ Kh8 29.Nxf5 Qe6 30.Rg1 a4 31.Rg4 Qb3 32.Qf1 a3 33.Rg3 Qxg3 0–1 1.e4 g6 2.d4 Bg7 3.Nc3 d6 4.f4 Nf6 5.Nf3 0-0 6.e5 Nfd7 7.h4 c5 8.h5 cxd4 9.hxg6 dxc3 10.gxf7+ Rxf7 11.Bc4 Nf8 12.Ng5 e6 13.Nxf7 cxb2 14.Bxb2 Qa5+ 15.Kf1 Kxf7 16.Qh5+ Kg8 17.Bd3 Qb4 18.Rb1 Bd7 19.c4 Qd2 20.Bxh7+ Nxh7 21.Qxh7+ Kf8 22.Rh4 1–0
 * In the following game, Azmaiparashvili uses the Pirc to defeat reigning world chess champion Karpov. Karpov vs. Azmaiparashvili, USSR Championship, Moscow 1983
 * Kasparov vs. Veselin Topalov, Wijk aan Zee 1999. Called Kasparov's Immortal, this game has been called "the most famous Pirc game of all time".
 * Mikhail Tal vs. Tigran Petrosian, Moscow 1974
 * Fischer vs. Viktor Korchnoi, Curaçao 1962
 * Hikaru Nakamura vs. Ilya Smirin, Foxwoods Open 2005

ECO codes
Some of the systems employed by White against the Pirc Defence include the following:
 * 4.Bc4 (ECO B07) Kholmov System (4.Bc4 Bg7 5.Qe2)
 * 4.Be2 (ECO B07) sub-variants after 4.Be2 Bg7 include the Chinese Variation, 5.g4, and the Bayonet (Mariotti) Attack, 5.h4
 * 4.Be3 (ECO B07) 150 or "Caveman" Attack (4.Be3 c6 5.Qd2)
 * 4.Bg5 (ECO B07) Byrne Variation
 * 4.g3 (ECO B07) Sveshnikov System
 * 4.Nf3 (ECO B08) Classical (Two Knights) System (sub-variants after 4...Bg7 include 5.h3 and 5.Be2)
 * 4.f4 (ECO B09) Austrian Attack (sub-variants after 4.f4 Bg7 5.Nf3 0-0 include 6.e5, 6.Be2, 6.Bd3 and 6.Be3; also, after 4...Bg7 is 5.Bc4, the Ljubojevic Variation; Black also has the option to move into the Dragon Formation after 5.Nf3 with 5...c5)

title: Pirc Defence


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Modern Defense

The Modern Defense (also known as the Robatsch Defence after Karl Robatsch) is a hypermodern chess opening in which Black allows White to occupy the with pawns on d4 and e4, then proceeds to attack and undermine this "ideal" center without attempting to occupy it.

The Modern Defense usually starts with the opening moves:
 * 1. e4 g6

The opening has been most notably used by British grandmasters Nigel Davies and Colin McNab.

The Modern Defense is closely related to the Pirc Defence, the primary difference being that in the Modern, Black delays developing the knight to f6. The delay of ...Nf6 attacking White's pawn on e4 gives White the option of blunting the g7-bishop with c2–c3. There are numerous transpositional possibilities between the two openings.

The Encyclopaedia of Chess Openings (ECO) classifies the Modern Defense as code B06, while codes B07 to B09 are assigned to the Pirc. The tenth edition of Modern Chess Openings (1965) grouped the Pirc and Robatsch together as the "Pirc–Robatsch Defense".

Main line: 2.d4 Bg7
White's strongest response to the Modern Defense is 2.d4, to which Black typically responds 2...Bg7. The main continuations are: Other possibilities include:
 * 3. Nc3 d6 4. f4 c6 5. Nf3 Bg4 (the Standard Line, ECO B06)
 * 3. c4 (ECO A40) d6 4. Nc3 Nc6 5. Be3 e5 6. d5 Nce7 (7.g4 will be answered by 7...f5 8.gxf5 gxf5 9.Qh5+ Ng6 10.exf5 Qh4 11.Qxh4 Nxh4 12.Nb5 Kd8)
 * 3.Bc4 (Bishop Attack)
 * 3.Bd2 (Westermann Gambit)
 * 3.Bd3 (Wind Gambit)
 * 3.f4 (Three Pawns Attack)
 * 3.g3
 * 3.Nf3

Fischer's 3.h4!?
Bobby Fischer suggested the move 3.h4!? as an unorthodox try against 1...g6 2.d4 Bg7, in his annotation to a game against Pal Benko. (Fischer played 3.Nc3 in the actual game.) The idea is to pry open Black's by h4–h5 followed by hxg6, as ...gxh5 would greatly weaken the cover to Black's king.

Averbakh System
The Modern Defense, Averbakh System (ECO A42) can be reached by the lines:

 * 1.e4 g6 2.d4 Bg7 3.c4 d6 4.Nc3 (diagram)
 * 1.d4 g6 2.c4 Bg7 3.Nc3 d6 4.e4 (diagram)

Possible moves for Black at this point include 4...Nf6, 4...Nc6, 4...e5, and 4...Nd7. The move 4...Nf6 leads to a position of the King's Indian Defence, where White has options 5.Nf3, 5.f3, 5.Be2, 5.f4, and so on.

Unusual White responses
The flexibility and toughness of the Modern Defense have provoked some very aggressive responses by White, including the crudely named Monkey's Bum, a typical sequence being 1.e4 g6 2.Bc4 Bg7 3.Qf3. (A more refined version is the Monkey's Bum Deferred, where White plays Bc4 and Qf3 only after developing the .)

Unusual Black responses
Other unusual openings can be reached after 1.e4 g6. The Hippopotamus Defence is one such system. Another is the Norwegian Defence (also known as the North Sea Defence) which begins 1.e4 g6 2.d4 Nf6 3.e5 Nh5. (If White plays 4.g4, Black retreats the knight with 4...Ng7. On 4.Be2, Black can retreat the knight or gambit a pawn with 4...d6!? If White plays 3.Nc3 instead of 3.e5, Black can transpose to the Pirc Defence with 3...d6 or continue in unconventional fashion with 3...d5!?)

Transpositions
Transpositions are possible after 2.c4, for example a Maróczy Bind results after 2...c5 3.Nf3 Bg7 (or Nc6) 4.d4 cxd4 5.Nxd4 and the Averbakh system is reached after 2...Bg7 3.d4 d6 4.Nc3. After 2.Nf3, Black can play 2...c5, transposing to the Sicilian Defense, or 2...Bg7. Following 2.Nc3, Black can transpose to a closed Sicilian with 2...c5  or play 2...Bg7.

Kavalek vs. Suttles
In the following game played at the Nice Olympiad in 1974, Canadian GM Duncan Suttles, one of the Modern's leading exponents, defeats Czech-American GM Lubomir Kavalek:
 * 1. e4 g6 2. d4 d6 3. Nf3 Bg7 4. Be2 Nf6 5. Nc3 (Pirc Defence by transposition) 5... a6 6. a4 0-0 7. 0-0 b6 8. Re1 Bb7 9. Bc4 e6 10. Bf4 Nbd7 11. Qd2 b5! (initiating a deep combination; Suttles later remarked that Kavalek has occupied the center and developed his pieces in the manner advocated by Fred Reinfeld, yet now stands worse) 12. axb5 axb5 13. Rxa8 Qxa8 14. Bxb5 Bxe4 15. Nxe4 Nxe4 16. Rxe4 Qxe4 17. Bxd7 Ra8 18. h4 Qb7! (despite his advantage, White is in trouble; note that his bishop on d7 is nearly trapped) 19. d5 e5 20. Bh6 Qxb2 21. h5 Ra1+ 22. Kh2 Qb1 23. Bxg7 Qh1+ 24. Kg3 Kxg7 25. Bh3 Qc1 26. h6+ Kf6 27. c4 Qxd2 28. Nxd2 Kg5 29. Ne4+ Kxh6 30. Bd7 f5 31. Nf6 Ra7 32. Bb5 g5 33. Ng8+ Kg7 34. Ne7 Kf6 35. Nc6 Ra3+ 36. Kh2 h5 37. Nb8 h4 38. Na6 g4 39. Nxc7 Ra2 40. Kg1 g3 41. fxg3 hxg3 42. Kf1 e4 0–1

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title: Modern Defense


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Queen's Gambit

The Queen's Gambit is the chess opening that starts with the moves:
 * 1. d4 d5
 * 2. c4

It is one of the oldest openings and is still commonly played today. It is traditionally described as a gambit because White appears to sacrifice the c-pawn; however, this could be considered a misnomer as Black cannot retain the pawn without incurring a disadvantage.

History
The Queen's Gambit is one of the oldest known openings in chess. It was mentioned in the Göttingen manuscript of 1490 and was later analyzed by Gioachino Greco in the 17th century. In the 18th century, it was recommended by Philipp Stamma of Aleppo and is sometimes known as the Aleppo Gambit in his honor. During the early period of modern chess, queen pawn openings were not in fashion, and the Queen's Gambit did not become commonplace until the 1873 tournament in Vienna.

As Wilhelm Steinitz and Siegbert Tarrasch developed chess theory and increased the appreciation of, the Queen's Gambit grew more popular, reaching its zenith in the 1920s and 1930s, and it was played in all but 2 of 34 games in the 1927 World Championship match between José Raúl Capablanca and Alexander Alekhine.

After the resumption of international chess activity following World War II, it was less frequently seen as many players moved away from symmetrical openings, tending to use an Indian Defence to combat queen pawn openings; however, it is still frequently played.

Overview
With 2.c4, White threatens to exchange a wing pawn (the c-pawn) for a center pawn (Black's d-pawn) in order to dominate the with e2–e4. Note that Black cannot hold the pawn, for example: 1.d4 d5 2.c4 dxc4 3.e3 b5 (Black tries to guard their pawn but should pursue with 3...Nf6 or 3...e5) 4.a4 c6? 5.axb5 cxb5 6.Qf3! winning a piece.

The Queen's Gambit is divided into two major categories based on Black's response: the Queen's Gambit Accepted (QGA) and the Queen's Gambit Declined (QGD). In the QGA, Black plays 2...dxc4, temporarily giving up the center to obtain freer development. In the QGD, Black usually plays to hold d5. Frequently Black will be cramped, but Black aims to exchange pieces and use at c5 and e5 to free Black's game.

Variations
Technically, any Black response other than 2...dxc4 (or another line with an early ...dxc4 that transposes into the QGA) is a Queen's Gambit Declined, but the Slav, Albin Countergambit, and Chigorin Defense are generally treated separately. There are so many QGD lines after 2...e6 that many of them are distinctive enough to warrant separate treatment. The Orthodox Defense and the Tarrasch Defense are two important examples. (See Queen's Gambit Declined for more.)

After 1.d4 d5 2.c4:
 * 2...e6 – Queen's Gambit Declined or QGD (ECO D30–D69). This is the main line, with many variations.
 * 2...dxc4 – Queen's Gambit Accepted or QGA (D20–D29). Less popular than the Queen's Gambit Declined, it nevertheless has a solid reputation.
 * 2...c6 – Slav Defense (D10–D19). This is a solid response, although many variations are very tactical. If Black plays both ...c6 and ...e6 (in either order), the opening takes characteristics of both the Slav and the Orthodox Defense and is classified as a Semi-Slav Defense.
 * 2...e5 – Albin Countergambit (D08–D09), a sharp attempt by Black to gain the initiative. It is uncommon in top-level chess but can be a dangerous weapon in club play.
 * 2...Nc6 – Chigorin Defense (D07) The Chigorin Defense takes the game away from the normal positional channels of the QGD and has been favored by Alexander Morozevich at the top level; it appears to be for Black.
 * 2...Bf5 – Baltic Defense (D06), an offbeat but playable line.
 * 2...c5 – Symmetrical Defense (D06). This is rarely played; although it has not been definitely refuted, the play seems to favor White.
 * 2...Nf6 – Marshall Defense (D06), named after Frank Marshall, who first devised the move, he briefly played it in the 1920s before abandoning it.
 * 2...g6?! – Alekhine idea (D06). White can gain the advantage by 3.cxd5 Qxd5 (3...Nf6 4.Qa4 ) 4.Nc3 Qa5 5.Nf3 Bg7 6.Bd2 c6 7.e4 Qb6 8.Bc4 Bxd4 9.Nxd4 Qxd4 10.Qb3 Qg7 11.0-0 +/− (Minev).

If White chooses to fianchetto the, the game transposes into the Catalan Opening.

title: Queen's Gambit


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King's Indian Defence

The King's Indian Defence (or KID) is a common chess opening. It is defined by the following moves:
 * 1. d4 Nf6
 * 2. c4 g6

Black intends to follow up with 3...Bg7 and 4...d6 (the Grünfeld Defence arises when Black plays 3...d5 instead and is considered a separate opening). White's major third move options are 3.Nc3, 3.Nf3 or 3.g3, with both the King's Indian and Grünfeld playable against these moves. The Encyclopaedia of Chess Openings classifies the King's Indian Defence under the codes E60 through E99.

The King's Indian is a hypermodern opening, where Black deliberately allows White control of the with pawns, with the view to subsequently challenge it. In the most critical lines of the King's Indian, White erects an imposing pawn centre with Nc3 followed by e4. Black stakes out their own claim to the centre with the Benoni-style ...c5, or ...e5. If White resolves the central pawn tension with d5, then Black follows with either ...b5 and queenside play, or ...f5 and an eventual kingside attack. Meanwhile, White attempts to expand on the opposite wing. The resulting unbalanced positions offer scope for both sides to play for a win.

History
The earliest known use of the term "Indian Defence" was in 1884. The modern names "King's Indian Defence", "King's Indian Attack", etc. arose in the mid-twentieth century and are attributed to Hans Kmoch. Until the mid-1930s, the King's Indian Defence was generally regarded as highly suspect, but the analysis and play of three strong Soviet players in particular—Alexander Konstantinopolsky, Isaac Boleslavsky, and David Bronstein—helped to make the defence much more respected and popular. It is a dynamic opening, exceptionally complex, and a favourite of former world champions Garry Kasparov, Bobby Fischer, and Mikhail Tal, with prominent grandmasters Viktor Korchnoi, Miguel Najdorf, Efim Geller, John Nunn, Svetozar Gligorić, Wolfgang Uhlmann, and Ilya Smirin having also contributed much to the theory and practice of this opening.

In the early 2000s the opening's popularity suffered after Vladimir Kramnik began scoring excellently against it, so much so that Kasparov gave up the opening after several critical losses to Kramnik. However, Kramnik himself won a game on the black side of the KID in 2012, and current top players including Hikaru Nakamura, Teimour Radjabov, and Ding Liren play the opening.

Variations
The main variations of the King's Indian are:

Classical Variation: 5.Nf3 0-0 6.Be2 e5
The Classical Variation is 3.Nc3 Bg7 4.e4 d6 5.Nf3 0-0 6.Be2 e5.
 * The Main Line or Mar del Plata Variation continues 7.0-0 Nc6 8.d5 Ne7. Now White has a wide variety of moves, including 9.b4, 9.Ne1, and 9.Nd2, among others. Typically, White will try to attack on the by preparing the pawn break c4–c5, while Black will attack on the  by transferring their knight from f6 to d7 (usually better placed than at e8, as it helps slow White's queenside play with c4–c5), and starting a kingside pawn storm with f7–f5–f4 and g6–g5. 9.b4, the Bayonet Attack, introduced by Korchnoi in the 1970s, used to put top players off playing this line, but it has recently been revived by Radjabov.
 * 7.0-0 Nbd7 is the Old Main Line, and is, though less common nowadays than 7...Nc6.
 * 7.0-0 exd4 8.Nxd4 is also possible, although White's extra space usually is of greater value than Black's counterplay against White's centre. Made popular in the mid-1990s by the Russian Grandmaster Igor Glek, new ideas were found for White yet some of the best lines for White were later refuted. White still has an advantage in most lines.
 * 7.0-0 Na6 has seen some popularity recently. The purpose of this awkward-looking move is to transfer the knight to c5 after White's eventual d5, while guarding c7 if Black should play ...Qe8. Play commonly continues 8.Be3 Ng4 9.Bg5 Qe8 but White has also tried:
 * 8.dxe5 dxe5 9.Qxd8 Rxd8 with even chances;
 * 8.d5 Nc5 9.Qc2 a5 may transpose into the Petrosian Variation (see below);
 * 8.Bg5 h6 9.Bh4 Qe8 10.Bxf6 Bxf6 11.c5!, which is not totally reliable for Black.
 * 7.d5 is the Petrosian Variation, so named for the 1963–69 world champion Tigran Petrosian, who often essayed the line in the 1960s, with Vladimir Kramnik playing this variation extensively in the 1990s. The plans for both sides are roughly the same as in the main variation. After 7...a5 White plays 8.Bg5 to pin the knight, making it harder for Black to achieve the ...f7–f5 break. In the early days of the system, Black would drive the bishop back with ...h6 and ...g5, though players subsequently switched to ideas involving ...Na6, ...Qe8 and ...Bd7, making White's c4–c5 break more difficult, only then playing for kingside activity. Joe Gallagher has recommended the flexible 7...Na6 which has similar ideas to 7...a5.
 * 7.Be3 is often known as the Gligoric System, after the World Championship Candidate Svetozar Gligorić, who has contributed much to King's Indian theory and practice with both colours. More recently, other strong players such as Korchnoi, Anatoly Karpov, and Kasparov have played this line. The main idea behind this move is to avoid the theoretical lines that arise after 7.0-0 Nc6. This move allows White to maintain, for the moment, the tension in the centre. If Black plays mechanically with 7...Nc6, 8.d5 Ne7 9.Nd2! is a favourable setup, so Black most often responds by crossing their opponent's plans with 7...Ng4 8.Bg5 f6 9.Bh4 Nc6, but other moves are also seen, such as:
 * 7...Na6 8.0-0 transposing into the modern.
 * 7...h6 is a favourite of John Nunn. The main line runs 8.0-0 Ng4 9.Bc1 Nc6 10.d5 Ne7 11.Ne1 f5 12.Bxg4 fxg4. In this subvariation, Black's kingside play is of a different type than normal KID lines, as it lacks the standard pawn breaks, so they will now play g6–g5 and Ng6–f4, often investing material in a piece attack in the f-file against the white king, while White plays for the usual queenside breakthrough with c4–c5.
 * 7...exd4 immediately surrenders the centre, with a view to playing a quick c7–c6 and d6–d5. For example, 8.Nxd4 Re8 9.f3 c6 10.Qd2 (10.Bf2!?) 10...d5 11.exd5 cxd5 12.0-0 Nc6 13.c5 and 13...Rxe3!? (which was first seen in game 11 of the 1990 World Chess Championship between Kasparov and Karpov).
 * In the Exchange Variation (7.dxe5 dxe5 8.Qxd8 Rxd8), White exchanges queens and is content to play for a small, safe advantage in the relatively quiet positions which will ensue in this queenless middlegame. The line is often played by White players hoping for an early draw, but there is still a lot of play left in the position. White tries to exploit d6 with moves such as b4, c5, Nf3–d2–c4–d6, etc., while Black will play to control the hole on d4. In practice, it is easier to exploit d4, and chances are balanced. If Black is able to play ...Nd4, they will often have at least an equal position, even when this involves the sacrifice of a pawn to eliminate White's dark-squared bishop.

Sidelines
A minor but still significant sideline occurs for White on move 6, with 6.Bg5, the Zinnowitz Variation, instead of 6.Be2 e5. The line was played several times by German Grandmaster Burkhard Malich in the 1960s and 1970s. It is currently unfashionable at master level; Black gets a good game with either 6...h6 or 6...Nbd7. This line is distinct from the much more popular Averbakh Variation, described below, since in the Zinnowitz, White has played 5.Nf3 instead of 5.Be2, as in the Averbakh, and then follows with 6.Bg5.

Another, more significant and quite popular sideline occurs for Black on move 6, with 6...Bg4, in place of the mainline 6...e5. One idea for Black here is to relieve their somewhat cramped position by exchanging their light-squared bishop, which is often relegated to a passive role in the King's Indian. White's most popular response is 7.Be3, similar to the Gligoric System (see above); White seems to retain a small edge in every variation. Top players who have used this line for Black include two former World Champions: GMs Mikhail Tal and Boris Spassky.

After 6...c5 7.O-O cxd4 8.Nxd4 Nc6, the game transposes into the Accelerated Dragon variation of the Sicilian Defence.

Sämisch Variation: 5.f3
The Sämisch Variation is 3.Nc3 Bg7 4.e4 d6 5.f3. It is named after Friedrich Sämisch, who developed the system in the 1920s. This often leads to very sharp play with the players castling on opposite wings and attacking each other's kings, as in the Bagirov–Gufeld game given below, though it may also give rise to heavyweight positional struggles. Black has a variety of pawn breaks, such as ...e5, ...c5 and ...b5 (prepared by ...c6 and/or ...a6). This can transpose to the Modern Benoni after 5...0-0 6.Bg5 c5 7.d5 e6. World champions Mikhail Botvinnik, Mikhail Tal, Tigran Petrosian, Boris Spassky, Anatoly Karpov and Garry Kasparov have all played this variation. This line defends the e4-pawn to create a secure centre and enables White to begin an attack kingside with Be3, Qd2, Bh6, g2–g4 and h2–h4. It allows placement of a bishop on e3 without allowing ...Ng4; however, its drawback is that it deprives the knight on g1 of its most natural square, thus impeding development of the kingside. Black can strike for the centre as previously mentioned or delay with 6...Nc6, 7...a6 and 8...Rb8 so that Black can play ...b7–b5 to open lines on the queenside.

The Classical Defence to the Sämisch is 5...0-0 6.Be3 e5, when White has a choice between closing the centre with 7.d5, or maintaining the tension with 7.Nge2. Kasparov was a major proponent of this defence.

The Sämisch Gambit arises after 5...0-0 6.Be3 c5. This is a pawn sacrifice, and was once considered dubious. As Black's play has been worked out, this evaluation has changed, and the gambit now enjoys a good reputation. A practical drawback, however, is that a well-prepared but unambitious White player can often enter lines leading to a forced draw. The line where White accepts the gambit runs 5...0-0 6.Be3 c5 7.dxc5 dxc5 8.Qxd8 (8.e5 Nfd7 9.f4 f6 10.exf6 is also possible here, though less often seen) Rxd8 9.Bxc5 Nc6. Black's activity is believed to give sufficient compensation. White's most frequent play is to decline the gambit, and instead play 7.Nge2, and head for Benoni type positions after a d4–d5 advance. However, after 7...cxd4 (preventing the d4-d5 advance) 8.Nxd4 Nc6, the game transposes into the Accelerated Dragon variation of the Sicilian Defence.

5...0-0 6.Be3 Nc6 7.Nge2 a6 8.Qd2 Rb8 leads to the Panno Variation of the Sämisch. Black prepares to respond appropriately depending on White's choice of plan. If White plays 0-0-0 and goes for a kingside attack, then 7...a6 prepares ...b7–b5 with a counterattack against White's castled position. If instead White plays more cautiously, then Black challenges White's centre with ...e5.

Averbakh Variation: 5.Be2 0-0 6.Bg5
The Averbakh Variation is 3.Nc3 Bg7 4.e4 d6 5.Be2 0-0 6.Bg5 (named for Yuri Averbakh), which prevents the immediate 6...e5 (6...e5 7. dxe5 dxe5 8. Qxd8 Rxd8 9. Nd5 Nxd5 (If black doesn't play Nxd5, black loses the f6 knight)10. Bxd8 Nb6 11. Bxc7 White is up an exchange and a pawn, the endgame should be winning for white.)

Black often repels the bishop with ...h6 giving them the option of a later g5, though in practice this is a weakening move. White has various ways to develop, such as Qd2, Nf3, f4 or even h4. However, Black obtains good play against all of these development schemes.

The old main line in this begins with 6...c5 (which keeps the long diagonal open).

However, 6...Nbd7 and 6...Na6 (Judit Polgár's move) are also seen.

It is possible that the Averbakh System (of the Modern Defense) can transition to the Averbakh Variation of the King's Indian Defence.

Four Pawns Attack: 5.f4
The Four Pawns Attack continues with 3.Nc3 Bg7 4.e4 d6 5.f4 0-0 6.Nf3. This is the most aggressive method for White, and was often seen in the 1920s. With their fifth move, White erects a massive centre at the price of falling behind in development. If Black can open the position, White may well find themselves overextended. From this 6...c5 is the main line.
 * 6...c5 7.d5 e6 8.Be2 exd5 9.cxd5
 * 9...Bg4 has been a solid line for Black.
 * 9...Re8 can be justified with solid play.
 * 9...b5 is known to lead to sharp, dangerous play.
 * 6...Na6 is known as the Modern Variation. This is a move anticipating playing ...Nc5 with counterplay. If white makes neutral moves such as 7.Bd3, this has had success. On the other hand, 7.e5 is the most aggressive plan.

Fianchetto Variation: 3.Nf3 Bg7 4.g3
The Fianchetto Variation 1.d4 Nf6 2.c4 g6 3.Nf3 Bg7 4.g3 0-0 5.Bg2 d6 6.0-0, is named for White's development of light-squared bishop to g2, and is one of the most popular lines at the grandmaster level, Korchnoi once its most notable practitioner. This method of development is on completely different lines than other King's Indian variations. Here, Black's normal plan of attack can hardly succeed, as White's kingside is more solidly defended than in most KID variations. The most common responses are:
 * 6...Nbd7 with 8...exd4. Black intends to claim the centre with ...e7–e5. 7.Nc3 e5 8.e4 exd4 9.Nxd4 Re8 10.h3 a6. Preparation has been made for 11...Rb8, with ...c7–c5 and ...b7–b5, and sometimes with ...Ne5 first. This is known as the Gallagher Variation of the Fianchetto Variation.
 * 8...c6 and 8...a6 are alternatives.
 * 6...Nc6 7.Nc3 a6 8.d5 Na5. This variation goes against ancient dogma which states that knights are not well placed on the rim; however, extra pressure is brought to bear against the Achilles Heel of the fianchetto lines—the weakness at c4. Hundreds of master games have continued with 9.Nd2 c5 10.Qc2 Rb8 11.b3 b5 12.Bb2 bxc4 13.bxc4 Bh6 14.f4 (14.e3 Bf5 is a trap that numbers Mark Taimanov among its victims; White must now lose material, as he has no good interposition) 14...e5!

Sidelines
Finally, White has other setups, such as Nf3 and h3 and Nge2 (with or without Bd3), but these are currently not as popular at the grandmaster level. 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nge2 followed by 6.Ng3 is called the Hungarian Attack.

Famous games
One of the earliest examples:

John Cochrane vs. Bonnerjee Mohishunder, Calcutta, India, 1851 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.f4 0-0 6.Nf3 e5 7.fxe5 dxe5 8.Nxe5 c5 9.d5 Nxe4 10.Nxe4 Qh4+ 11.Nf2 Bxe5 12.g3 Qf6 13.Qe2 Bc3+ 14.Kd1 Bd4 15.Ne4 Qa6 16.Bh6 Rd8 17.Bg2 Nd7 18.Rf1 f5 19.Ng5 Ne5 20.Nf3 Nxf3 21.Bxf3 Bd7 22.Kc2 Re8 23.Qd3 f4 24.Rae1 Bf5 25.Be4 Rxe4 26.Rxe4 Bxe4

One of the most famous King's Indian games was a by the late Ukrainian-American grandmaster Eduard Gufeld, who called it his "Mona Lisa":

Vladimir Bagirov vs. Eduard Gufeld, USSR championship 1973 1.d4 g6 2.c4 Bg7 3.Nc3 d6 4.e4 Nf6 5.f3 0-0 6.Be3 Nc6 7.Nge2 Rb8 8.Qd2 a6 9.Bh6 b5 10.h4 e5 11.Bxg7 Kxg7 12.h5 Kh8 13.Nd5 bxc4 14.hxg6 fxg6 15.Qh6 Nh5 16.g4 Rxb2 17.gxh5 g5 18.Rg1 g4 19.0-0-0 Rxa2 20.Nef4 exf4 21.Nxf4 Rxf4 22.Qxf4 c3 23.Bc4 Ra3 24.fxg4 Nb4 25.Kb1 Be6 26.Bxe6 Nd3 27.Qf7 Qb8+ 28.Bb3 Rxb3+ 29.Kc2 Nb4+ 30.Kxb3 Nd5+ 31.Kc2 Qb2+ 32.Kd3 Qb5+

ECO codes
The Encyclopaedia of Chess Openings classification of variations of the King's Indian are:
 * E60 King's Indian Defence
 * E61 King's Indian Defence, 3.Nc3
 * E62 King's Indian, Fianchetto Variation
 * E63 King's Indian, Fianchetto, Panno Variation
 * E64 King's Indian, Fianchetto, Yugoslav system
 * E65 King's Indian, Yugoslav, 7.0-0
 * E66 King's Indian, Fianchetto, Yugoslav Panno
 * E67 King's Indian, Fianchetto with ...Nbd7
 * E68 King's Indian, Fianchetto, Classical Variation, 8.e4
 * E69 King's Indian, Fianchetto, Classical Main line
 * E70 King's Indian, 4.e4
 * E71 King's Indian, Makogonov system (5.h3)
 * E72 King's Indian with e4 and g3
 * E73 King's Indian, 5.Be2
 * E74 King's Indian, Averbakh, 6...c5
 * E75 King's Indian, Averbakh, Main line
 * E76 King's Indian, Four Pawns Attack
 * E77 King's Indian, Four Pawns Attack, 6.Be2
 * E78 King's Indian, Four Pawns Attack, with Be2 and Nf3
 * E79 King's Indian, Four Pawns Attack, Main line
 * E80 King's Indian, Sämisch Variation
 * E81 King's Indian, Sämisch, 5...0-0
 * E82 King's Indian, Sämisch, 6...b6
 * E83 King's Indian, Sämisch, 6...Nc6
 * E84 King's Indian, Sämisch, Panno Main line
 * E85 King's Indian, Sämisch, Orthodox Variation
 * E86 King's Indian, Sämisch, Orthodox, 7.Nge2 c6
 * E87 King's Indian, Sämisch, Orthodox, 7.d5
 * E88 King's Indian, Sämisch, Orthodox, 7.d5 c6
 * E89 King's Indian, Sämisch, Orthodox Main line
 * E90 King's Indian, 5.Nf3
 * E91 King's Indian, Kazakh variation, 6.Be2
 * E92 King's Indian, Classical Variation
 * E93 King's Indian, Petrosian system, Main line
 * E94 King's Indian, Orthodox Variation
 * E95 King's Indian, Orthodox, 7...Nbd7, 8.Re1
 * E96 King's Indian, Orthodox, 7...Nbd7, Main line
 * E97 King's Indian, Orthodox, Aronin–Taimanov Variation (Yugoslav Attack / Mar del Plata Variation)
 * E98 King's Indian, Orthodox, Aronin–Taimanov, 9.Ne1
 * E99 King's Indian, Orthodox, Aronin–Taimanov, Main

title: King's Indian Defence


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Price stability

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title: Price stability


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Bogo-Indian Defence

The Bogo-Indian Defence is a chess opening characterised by the moves:
 * 1. d4 Nf6
 * 2. c4 e6
 * 3. Nf3 Bb4+

The position after 1.d4 Nf6 2.c4 e6 is common. The traditional move for White here is 3.Nc3, threatening to set up a big pawn centre with 4.e4. However, 3.Nf3 is often played instead as a way of avoiding the Nimzo-Indian Defence (which would follow after 3.Nc3 Bb4). After 3.Nf3, Black usually plays 3...b6 (the Queen's Indian Defence) or 3...d5 (transposing to the Queen's Gambit Declined), but can instead play 3...Bb4+, the Bogo-Indian Defence. Databases suggest that the Bogo-Indian is played approximately half as often as the Queen's Indian.

The Bogo-Indian Defence can also arise via the move order 1.d4 e6 2.c4 Bb4+, the Keres Defence.

The Bogo-Indian is classified as E11 by the Encyclopaedia of Chess Openings (ECO).

History
The Bogo-Indian Defence is named after the Russian-born German master Efim Bogoljubow who is believed to have originated the opening and played it regularly in the 1920s. Subsequent prominent players to have adopted the Bogo-Indian include Aron Nimzowitsch, Paul Keres, Tigran Petrosian, Bent Larsen, Vasily Smyslov, Viktor Korchnoi, Ulf Andersson, Michael Adams and Nikita Vitiugov.

Variations
White has three viable moves to meet the check. 4.Nc3 is a transposition to the Kasparov Variation of the Nimzo-Indian, therefore the main independent variations are 4.Bd2 and 4.Nbd2.

4.Bd2
4.Bd2 is the most common line; the bishop on b4 is now threatened and Black must decide how to meet this threat.

 * 4...Qe7 is now the most frequently played option. After 5. g3 Nc6, the main line continues 6. Nc3 Bxc3 7. Bxc3 Ne4 8. Rc1 0-0 9. Bg2 d6 10. d5 Nd8 11. dxe6 Nxe6 and the position is equal (see diagram). An alternative line is 6. Bg2 Bxd2+ 7. Nbxd2 d6 8. 0-0 a5 9. e4 e5 10. d5 Nb8 11. Ne1 0-0 12. Nd3 Na6 and the position is again equal.

 * David Bronstein tried the sharper alternative 4...a5, grabbing space on the queenside at the cost of structural weaknesses.
 * The simplest is to trade off the bishop by means of 4...Bxd2+; this line is not particularly popular, but has been played frequently by the Swedish grandmaster Ulf Andersson, often as a drawing line.

 * A more modern line is 4...c5, after 5.Bxb4 cxb4, Black's pawns are doubled, and a pawn has been pulled away from the centre, but the b4 pawn can also be annoying for White since it takes the c3-square away from the knight. In fact, one of White's major alternatives is 6.a3, trading off this pawn at once.
 * Simply retreating the bishop by means of 4...Be7 is also possible; Black benefits from losing a tempo since White's dark-square bishop is misplaced at d2. The line is somewhat passive, but solid.

4.Nbd2
4.Nbd2 is an alternative aiming to acquire the bishop for the knight or forcing Black's bishop to retreat. The downside is that the knight is developed to a square where it blocks the bishop, and d2 is a less active square than c3. The line is described in the Gambit Guide as "ambitious". Black's most common replies are 4...b6, 4...0-0, and 4...d5.

Monticelli Trap
This opening can sometimes give rise to the Monticelli Trap.

title: Bogo-Indian Defence


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Queen's Indian Defense

The Queen's Indian Defense (QID) is a chess opening defined by the moves:
 * 1. d4 Nf6
 * 2. c4 e6
 * 3. Nf3 b6

The opening is a solid defense to the Queen's Pawn Game. 3...b6 increases Black's control over the central light squares e4 and d5 by preparing to fianchetto the, with the opening deriving its name from this maneuver. As in the other Indian defenses, Black attempts to control the with pieces in hypermodern style, instead of occupying it with pawns in classical style.

By playing 3.Nf3, White sidesteps the Nimzo-Indian Defense that arises after 3.Nc3 Bb4. The Queen's Indian is regarded as the sister opening of the Nimzo-Indian, since both openings aim to impede White's efforts to gain full control of the center by playing e2–e4. Together, they are a well-respected response to 1.d4.

Main line: 4.g3
4. g3 (ECO E15–E19) has long been White's most popular line against the Queen's Indian. It contests the by preparing to fianchetto the light-squared bishop. The standard response for Black through the 1970s was 4...Bb7, but 4...Ba6 has since become the topical line. A rarer third option is 4...Bb4+, which aims to exchange the less useful dark-squared bishop, though this line tends to leave Black with a slightly passive position.

Modern main line: 4...Ba6
White can defend the pawn at c4 with a piece by playing 5.Nbd2, 5.Qa4, 5.Qc2 or 5.Qb3, but these moves all diminish control of d4, making ...c7–c5 an effective reply for Black; therefore '''5. b3''' is White's most common response. However, it weakens the dark squares slightly, which Black can take advantage of by playing 5... Bb4+. Now 6.Nbd2 loses material after 6...Bc3 7.Rb1 Bb7 threatening 8...Be4, an opening trap which has ensnared players such as Kamran Shirazi. White's best move is therefore '''6. Bd2'''. However, after '''6... Be7 7. Bg2 c6''' Black is ready to play ...d7–d5, again attacking the c-pawn. If White plays cxd5 then ...cxd5 is considered to for Black. Thus White usually plays '''8. Bc3 to clear the d2-square, and after 8... d5''' White can play in two ways. After '''9. Nbd2 Nbd7 10. 0-0 0-0 11. Re1 c5 Black has achieved his thematic before White and the resulting position after 12. e4 dxe4 13. Nxe4''' is equal. Therefore, the main line continues '''9. Ne5 and since Black does not want White to maintain this knight on a strong central outpost, play continues 9... Nfd7 10. Nxd7 Nxd7 11. Nd2 0-0 12. 0-0 Rc8 13. e4'''. By diverting the black knight on move 9 it is now White who has achieved his central pawn break first. The effect of Black's check 5...Bb4+ has been to lure White's bishop to c3 where it blocks the c-file. This, the current main line of the Queen's Indian, is considered equal by theory and became a frequent guest in grandmaster praxis in the 1980s.

After '''5. b3, Black also has several playable alternatives to 5...Bb4+, the most common of which is 5... Bb7 6. Bg2 Bb4+ 7. Bd2 a5'''. When White plays Nc3, Black will exchange bishop for knight in order to enhance his control over the central light squares, and play on the with moves such as ...a5–a4 and ...b5. Other possibilities for Black include 5...d5 and 5...b5.

More recently, several grandmasters, including Alexander Beliavsky, Ni Hua, Veselin Topalov, and Magnus Carlsen, have played '''5. Qc2'''. The idea is to allow Black's counterthrust ...c5, the main line running '''5... Bb7 6. Bg2 c5'''. The fashion is for White to sacrifice a pawn with '''7. d5''', gaining active play. This idea has scored well for White, and new ideas have been cropping up since 2008. The 5.Qc2 lines had previously scored poorly for White according to Emms.

Old main line: 4...Bb7
The classical main line of the Queen's Indian, the most frequently played line from the 1950s until 4...Ba6 became popular in the 1980s, usually continues: '''5. Bg2 Be7 6. 0-0 0-0 7. Nc3 Ne4 8. Qc2 Nxc3 9. Qxc3'''. White has a, but Black has no weaknesses and can choose from a variety of ways to create counterplay, such as 9... c5, 9... f5 or 9... Be4. These lines are well known for their drawish tendencies and 4... Bb7 is nowadays often employed by Black as a drawing weapon. White has tried various deviations from the main line in an attempt to unbalance the play. These include:
 * 8. Bd2, which defends the knight on c3 and threatens a d4–d5 push.
 * 7. d5, introduced by Arturo Pomar, and rejuvenated by Lev Polugaevsky's continuation 7... exd5 8. Nh4 threatening to regain the pawn on d5 or to play Nf5.
 * 6. Nc3, which postpones castling in favor of preparing action in the center with the d4–d5 and e2–e4 thrusts.

4.a3
The Petrosian Variation, prepares 5.Nc3 by stopping ...Bb4 pinning the knight. White intends to follow up with Nc3 and e4, building a large pawn center. Black usually responds by contesting the e4-square with ...Bb7 and ...d5. (See Gurevich, 1992, for an extensive analysis.) This variation was often used by Garry Kasparov early in his career.

4.Nc3
Black can choose between 4...Bb7 and 4...Bb4.
 * 4... Bb7
 * 5. a3 became the more common move order to reach the Petrosian system by the mid-1980s, where White has avoided 4.a3 c5 5.d5 Ba6 and 4.a3 Ba6.
 * 5. Bg5 is an older line which gives Black good equalizing chances after 5...h6 6.Bh4 g5 7.Bg3 Nh5 8.e3 Nxg3 9.hxg3 Bg7. After 5...Be7, White can play 6.e3 or 6.Qc2.
 * 4... Bb4 (or the 3.Nc3 Bb4 4.Nf3 b6) is a Queen's Indian/Nimzo-Indian line. Moves for White include 5.Bg5, 5.e3, and 5.Qb3.
 * After 5. Bg5, Black may play 5...Bb7 or 5...h6.
 * 5...Bb7 6.e3 h6, White can play 7.Bh4.
 * 5...h6 6.Bh4 Bb7 (or by transposition 4...Bb7 5.Bg5 h6 6.Bh4 Bb4), White can play 7.e3. The position after 6...g5 7.Bg3 Ne4 8.Qc2 was heavily played and analyzed in the 1980s.
 * After 5. e3, Black usually plays 5...Bb7. White usually plays 6.Bd3 for the Fischer Variation of the Nimzo-Indian (or by transposition 3.Nc3 Bb4 4.e3 b6 5.Bd3 Bb7 6.Nf3). White can play 6.e3, then Black usually plays 6...h6, although 6.Nd2 or 6.Qc2 may be better.
 * After 5. Qb3, Black usually plays 5...c5.

4.e3
Preparing to develop the and castle, was also a favorite of Tigran Petrosian. This apparently quiet development may lead to complex middlegame play. Black usually replies 4...Bb7, then play may continue 5.Bd3 d5 6.0-0 or 5.Nc3 Bb4, transposing into the Nimzo-Indian Defence.

4.Bf4
The Miles Variation, which simply develops the bishop to a good square. Despite some success by its originator, this idea has never been popular.

ECO codes
The Encyclopaedia of Chess Openings classifies the Queen's Indian under codes E12 to E19 according to the following scheme:
 * E12 – 1.d4 Nf6 2.c4 e6 3.Nf3 b6
 * E13 – 1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.Nc3 Bb7 5.Bg5
 * E14 – 1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.e3
 * E15 – 1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.g3
 * E16 – 1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.g3 Bb7
 * E17 – 1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.g3 Bb7 5.Bg2 Be7
 * E18 – 1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.g3 Bb7 5.Bg2 Be7 6.0-0 0-0 7.Nc3
 * E19 – 1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.g3 Bb7 5.Bg2 Be7 6.0-0 0-0 7.Nc3 Ne4 8.Qc2

title: Queen's Indian Defense


text:
Kikka

Kikka may refer to:

 * Kikka, Estonia, a village in Estonia
 * Kikka Hanazawa (born 1970), Japanese investor and fashion industry executive
 * Kikka Sirén (1964–2005), Finnish singer
 * Nakajima Kikka, a Japanese jet aircraft
 * Kikka!, a 2022 film about the singer Kikka Sirén

title: Kikka


text:
Dutch Defence

The Dutch Defence is a chess opening characterised by the moves:
 * 1. d4 f5

Black's 1...f5 stakes a claim to the e4-square and envisions an attack in the middlegame on White's ; however, it also weakens Black's kingside to an extent (especially the e8–h5 diagonal). Like its 1.e4 counterpart, the Sicilian Defence, the Dutch is an aggressive and unbalancing opening, resulting in the lowest percentage of draws among the most common replies to 1.d4. Historically, White has tried many methods to exploit the kingside weaknesses, such as the Staunton Gambit (2.e4) and Korchnoi Attack (2.h3 and 3.g4).

The Dutch has never been a main line against 1.d4 and is rarely seen today in high-level competition, although a number of top players, including Alexander Alekhine, Bent Larsen, Paul Morphy, Miguel Najdorf, and Hikaru Nakamura have used it with success. Its most notable use may have been in 1951, when both world champion Mikhail Botvinnik and his challenger, David Bronstein, played it in their 1951 World Championship match.

History
Elias Stein (1748–1812), an Alsatian who settled in The Hague, recommended the defence as the best reply to 1.d4 in his 1789 book Nouvel essai sur le Jeu des échecs, avec des réflexions militaires relatives à ce jeu.

Siegbert Tarrasch rejected the opening as unsound in his 1931 work The Game of Chess, arguing that White should reply with the Staunton Gambit, with White being better after 2.e4 fxe4 3.Nc3 Nf6 4.Bg5 c6 5.f3 exf3.

Theory
White most often fianchettoes the king's bishop with g3 and Bg2. Black also sometimes fianchettoes the king's bishop with ...g6 and ...Bg7 (the Leningrad Dutch), but may instead develop the bishop to e7, d6 (after ...d5), or b4 (the latter is most often seen if White plays c4 before castling). Play often runs 2.g3 Nf6 3.Bg2 e6 4.Nf3 (4.Nh3 is also possible, intending Nf4–d3 to control the e5-square Black plays the Stonewall Variation) 4...Be7 5.0-0 0-0 6.c4 and now Black chooses between 6...d5 (the characteristic move of the Stonewall), 6...d6, the Ilyin-Zhenevsky Variation (less popular today), or Alekhine's move 6...Ne4!? retaining the option of moving the d-pawn either one or two squares.

The opening's attacking potential is shown in the Polish Immortal, in which Miguel Najdorf, using the Stonewall Variation, sacrificed all of his to win by checkmate.

Practitioners
The Stonewall Dutch enjoyed a resurgence of interest in the 1980s and 1990s, when leading grandmasters (GMs) Artur Yusupov, Sergey Dolmatov, Nigel Short and Simen Agdestein helped develop the system where Black plays an earlier ...d5 and places his dark-squared bishop on d6. Termed the Modern Stonewall, this setup has remained more popular than the traditional early ...Be7.

Magnus Carlsen has used the Stonewall to score wins against Viswanathan Anand and Fabiano Caruana.

Simon Williams is one of the leading practitioners of the classical Dutch and wrote more than one book on the opening.

White continuations
The traditional move order involves White playing 2.c4. More commonly, White will start with 2.g3. Some common variations are: c4 is played after g3 and Bg2; c4 is played after Nf3; and c4 is played after 0-0.

Examples:
 * traditional: 2.c4 Nf6 3.g3 g6 4.Bg2 Bg7 5.Nf3 0-0 6.0-0 d6
 * common: 2.g3 Nf6 3.Bg2 g6 4.Nf3 Bg7 5.0-0 0-0 6.c4 d6 (see diagram)

Other second moves
White has various more aggressive alternatives to the standard moves, including
 * 2.Nc3 Nf6 (or 2...d5) 3.Bg5, the Raphael Variation
 * 2.Bg5, the Hopton Attack; e.g. 2...Nf6 (2...g6 is the most popular move) 3. Bxf6 exf6 4. e3 or e4
 * 2.Bf4 or 2.Nf3 and 3.Bf4, the London System
 * 2.g4, Krejcik Gambit
 * 2.e4!?, the Staunton Gambit, named after Howard Staunton, who introduced it in his match against Bernhard Horwitz. The Staunton Gambit was once a feared attacking line, but it has been out of favour for over 80 years. GM Larry Christiansen and International Master Jeremy Silman have opined that it "offers White equality at best."
 * Carl Mayet introduced a completely different gambit approach to the Dutch in 1839 against von der Lasa, playing 2.h3 followed by 3.g4. Von der Lasa later published analysis of this line in the first edition of the Handbuch des Schachspiels. Viktor Korchnoi, one of the world's leading players, reintroduced the line into tournament practice in Korchnoi–Känel, Biel 1979. GM Christiansen later concluded, as von der Lasa and Staunton had done over 140 years earlier, that Black could get a good game by declining the gambit with 2...Nf6 3.g4 d5!
 * 2.Qd3, the Alapin Variation

Black sometimes starts with the move order 1...e6 to avoid these lines, although Black must then be ready to play the French Defence if White continues 2.e4, rendering the Dutch no longer an option. The Staunton Gambit remains a good choice of opening for White in blitz tournaments where Black has little time to ponder the most accurate defense.

ECO
The Encyclopaedia of Chess Openings has twenty codes for the Dutch Defence, A80 through A99.
 * A80: 1.d4 f5
 * A81: 1.d4 f5 2.g3 (Fianchetto Attack)
 * A82: 1.d4 f5 2.e4 (Staunton Gambit)
 * A83: 1.d4 f5 2.e4 fxe4 3.Nc3 Nf6 4.Bg5 (Staunton Gambit)
 * A84: 1.d4 f5 2.c4
 * A85: 1.d4 f5 2.c4 Nf6 3.Nc3 (Rubinstein Variation)
 * A86: 1.d4 f5 2.c4 Nf6 3.g3 (Fianchetto Variation)
 * A87: 1.d4 f5 2.c4 Nf6 3.g3 g6 4.Bg2 Bg7 5.Nf3 (Leningrad Dutch)
 * A88: 1.d4 f5 2.c4 Nf6 3.g3 g6 4.Bg2 Bg7 5.Nf3 0-0 6.0-0 d6 7.Nc3 c6 (Leningrad Dutch, Warsaw Variation)
 * A89: 1.d4 f5 2.c4 Nf6 3.g3 g6 4.Bg2 Bg7 5.Nf3 0-0 6.0-0 d6 7.Nc3 Nc6 (Leningrad Dutch, Matulovich)
 * A90: 1.d4 f5 2.c4 Nf6 3.g3 e6 4.Bg2 (Classical Variation)
 * A91: 1.d4 f5 2.c4 Nf6 3.g3 e6 4.Bg2 Be7
 * A92: 1.d4 f5 2.c4 Nf6 3.g3 e6 4.Bg2 Be7 5.Nf3 0-0
 * A93: 1.d4 f5 2.c4 Nf6 3.g3 e6 4.Bg2 Be7 5.Nf3 0-0 6.0-0 d5 7.b3 (Botvinnik Variation)
 * A94: 1.d4 f5 2.c4 Nf6 3.g3 e6 4.Bg2 Be7 5.Nf3 0-0 6.0-0 d5 7.b3 c6 8.Ba3 (Stonewall)
 * A95: 1.d4 f5 2.c4 Nf6 3.g3 e6 4.Bg2 Be7 5.Nf3 0-0 6.0-0 d5 7.Nc3 c6 (Stonewall)
 * A96: 1.d4 f5 2.c4 Nf6 3.g3 e6 4.Bg2 Be7 5.Nf3 0-0 6.0-0 d6
 * A97: 1.d4 f5 2.c4 Nf6 3.g3 e6 4.Bg2 Be7 5.Nf3 0-0 6.0-0 d6 7.Nc3 Qe8 (Ilyin–Genevsky Variation)
 * A98: 1.d4 f5 2.c4 Nf6 3.g3 e6 4.Bg2 Be7 5.Nf3 0-0 6.0-0 d6 7.Nc3 Qe8 8.Qc2 (Ilyin–Genevsky Variation)
 * A99: 1.d4 f5 2.c4 Nf6 3.g3 e6 4.Bg2 Be7 5.Nf3 0-0 6.0-0 d6 7.Nc3 Qe8 8.b3 (Ilyin–Genevsky Variation)

title: Dutch Defence


text:
English Opening

The English Opening is a chess opening that begins with the move:
 * 1. c4

A flank opening, it is the fourth most popular and, according to various databases, one of the four most successful of White's twenty possible first moves. White begins the fight for the by staking a claim to the d5-square from the wing, in hypermodern style. Although many lines of the English have a distinct character, the opening is often used as a transpositional device in much the same way as 1.Nf3 – to avoid such highly regarded responses to 1.d4 as the Nimzo-Indian and Grünfeld Defences – and is considered reliable and flexible.

History of the opening
The English derives its name from the leading 19th century English master Howard Staunton, who played it during his 1843 match with Saint-Amant and at London 1851, the first international tournament. It did not inspire Staunton's contemporaries and caught on only in the twentieth century. It is now recognised as a opening that may be used to reach both classical and hypermodern chess positions. Mikhail Botvinnik, Tigran Petrosian, Anatoly Karpov, Garry Kasparov, Magnus Carlsen, and Ding Liren have employed it during their world championship matches. Bobby Fischer created a stir when he switched to it from his customary 1.e4 late in his career, employing it against Lev Polugaevsky and Oscar Panno at the Palma de Mallorca Interzonal in 1970, and in his world championship match against Boris Spassky.

Taxonomy
Opening theoreticians who write on the English Opening divide it into three broad categories, generally determined by Black's choice of defensive setup.

Symmetrical Defence: 1...c5
The Symmetrical Defence (classified A30–39 in ECO) is 1...c5, and is so named because both of the c-pawns are advanced two squares, maintaining symmetry. Note that Black can reach the Symmetrical Defence through many move orders by deferring ...c5, and often does. For example, 1.c4 Nf6 2.Nc3 (or 2.Nf3) c5.

Either player may make an early break in the centre with the d-pawn. Similar to the Open Sicilian, an early d2–d4 for White can arise on the third move in the Symmetrical Defence with 2.Nf3, where Black has chosen one of 2...Nc6, 2...e6, 2...d6, or 2...g6.

After 3.d4, the game usually continues with 3...cxd4 4.Nxd4. The games can give a large variety of positional and tactical ideas, and can transpose into variants of the Open Sicilian involving the Maróczy Bind, such as the Accelerated Dragon, Taimanov, Kan, or Kalashnikov Variations, if White plays e4 in a later move. If Black manages to play d5 before White plays e4, then the game could transpose into variants of the Queen's Gambit Declined.

When Black plays 2...Nf6, these lines are often called the Anti-Benoni, since these positions are often reached after the transposition 1.d4 Nf6 2.c4 c5 3.Nf3, where White avoided the Benoni Defense that would arise after 3.d5. After 3...cxd4 4.Nxd4, Black could follow up with 4...e5 forcing White's knight to go to the queenside and avoiding the transpositions to the Sicilian or the QGD; however, White could avoid the line by first playing 3.Nc3 and then play 4.d4, if Black doesn't play 3...d5 (see below). Same as above, the position could transpose into a Queen's Gambit Declined or an Open Sicilian involving the Maróczy Bind.
 * With 2.e3 Nf6, the position transposes into a Panov–Botvinnik Attack after 3.d4 cxd4 4.exd4 d5. Alternatively, the position could transpose into a Tarrasch Defense in the Queen's Gambit Declined.
 * A typical line of play where Black plays an early ...d5 is 1.c4 c5 2.Nc3 Nf6 3.Nf3 d5, when White usually trades off in the centre 4.cxd5 Nxd5. White can either challenge the centre with 5.d4 or 5.e4 or allow Black a advantage in the centre with 5.g3. In the latter case, Black can play 5...Nc6 6.Bg2 Nc7 followed by 7...e5, reaching a reversed Maróczy Bind position called the Rubinstein System.

There are several types of positions that can arise from the Symmetrical Defence. Among the ideas are:
 * The Hedgehog system involves a solid but flexible defence in which Black develops by b6, e6, Bb7, and Be7, before controlling the fifth rank with moves such as a6 and d6. The game typically involves extended maneuvering, but both players need to be on the lookout for favourable pawn advances and.
 * The double fianchetto defence involves Black developing both bishops by fianchetto to g7 and b7. The line is fairly solid and difficult to defeat at the grandmaster level. Some lines are considered highly drawish, for instance if White's bishops are also fianchettoed to g2 and b2 there may be many piece exchanges leading to a simplified and equal position.

Reversed Sicilian: 1...e5
The Reversed Sicilian (classified A20–29 in ) is another broad category of defence, introduced by the response 1...e5. Note again, that Black can delay playing ...e5, for example 1.c4 Nf6 2.Nc3 Nc6 3.Nf3 e5 whereupon even though ...e5 has been delayed, once it is played the defence is classified as a Reversed Sicilian.

After 1...e5, White has Black's position in the Sicilian but with an extra tempo. This is often called the Reversed Sicilian, though others call it the King's English. Bruce Leverett, writing the English chapter in MCO-14, stated, "It is natural to treat the English as a Sicilian reversed, but the results are often surprising—main lines in the Sicilian Defence correspond to obscure side variations in the English, and vice versa."

Other lines
The third broad category consists of the non-...e5 and non-...c5 responses, classified A10–19 in ECO. Most often these defences consist of Nf6, e6, and d5 or Bb4 systemic responses by Black, or a Slav-like system consisting of c6 and d5, a direct King's Indian Defence setup with Nf6, g6, Bg7, 0-0, after which c5 and e5 are eschewed, or 1...f5, which usually transposes to a Dutch Defence once White plays d4. All irregular responses such as 1...b6 and 1...g5 are also lumped into this third broad category.
 * 1...Nf6 is the most common response to 1.c4, often played to arrive at an Indian Defence. More than half the time, however, Black subsequently elects to transpose into either a Symmetrical Defence with ...c5, or a Reversed Sicilian with ...e5.
 * 1...e6 can lead to a Queen's Gambit Declined after 2.Nc3 d5 3.d4, but White often prefers 2.Nf3, which may lead to a variety of openings.
 * 1...f5 leads to a Dutch Defence when White follows up with d4. Other choices for White are 2.Nc3, 2.Nf3, and 2.g3, where Black usually plays ...Nf6.
 * 1...g6 may lead to a Modern Defense, or after Nf6 and d6 or d5 to the King's Indian Defence or the Grünfeld Defence, respectively, or stay within English lines. Often dubbed the Great Snake Variation.
 * 1...c6 can lead to a Slav Defense after 2.d4 d5, but White will often prefer a Caro–Kann Defence with 2.e4 d5, or a Réti Opening after 2.Nf3 d5 3.b3. 1.c4 c6 2.d4 d6 is the Anglo-Slav Opening.
 * 1...b6 is the English Defence. This setup involves the fianchetto of the queenside bishop and 2...e6. Often Black will defer the move Nf6, choosing to attack the centre with f5 and/or Qh4. The English grandmasters Tony Miles and Jonathan Speelman have successfully used this opening.
 * 1...d5 is the Anglo-Scandinavian Defense. Thought of as inferior to the Scandinavian Defense due to exchanging the c-pawn for a center pawn, in addition to the Scandinavian already having a somewhat suspect reputation.
 * 1...g5 is an eccentric response known as Myers' Defense after Hugh Myers's advocacy of it in print and actual play. It is intended as an improved Grob's Attack; after 2.d4, Black will put pressure on the d4-square with moves such as ...Bg7, ...c5, and ...Qb6. According to Nunn's Chess Openings, White obtains a small advantage after 2.d4 Bg7 (offering a Grob-like : 3.Bxg5 c5) 3.Nc3 h6 4.e4. Myers recommended 3...c5 (instead of 3...h6); in response, Joel Benjamin advocates 4.dxc5
 * 1...b5 is called the Jaenisch Gambit after Carl Jaenisch. Black obtains no immediate compensation for the sacrificed pawn.

Transposition potential
If White plays an early d4, the game will usually transpose into either the Queen's Gambit or an Indian Defence. For example, after 1.c4 Nf6 2.Nc3 g6 3.d4 d5 the game has transposed into the Grünfeld Defence, usually reached by the move order 1.d4 Nf6 2.c4 g6 3.Nc3 d5.

White can, however, also play 1.c4 Nf6 2.Nc3 g6 3.e4, making it impossible for Black to reach a Grünfeld, instead more or less forcing them into lines of the King's Indian Defence with 3...d6. Black also cannot force a Grünfeld with 1.c4 Nf6 2.Nc3 d5, since White can deviate with 3.cxd5 Nxd5 4.g3, a line played several times by Mikhail Botvinnik in 1958, in his final match for the world championship with Vasily Smyslov.

Instead of playing an early d4, White can also play Nf3 and fianchetto the (g3 and Bg2), transposing into a Réti Opening.

Also, after 1.c4 c6, White can transpose into the Polish Opening, Outflank Variation, by playing 2.b4, which can be used as a surprise weapon if Black does not know very much about the Polish Opening.

The many different transpositional possibilities available to White make the English a slippery opening for Black to defend against, and make it necessary for them to consider carefully what move order to employ. For instance, if Black would like to play a Queen's Gambit Declined (QGD), the most accurate move order to do so is 1...e6 2.d4 d5. (Of course, White can again play the Réti instead with 2.Nf3 d5 3.b3.) If Black plays instead 1...Nf6 2.Nc3 e6, White can avoid the QGD by playing 3.e4, the Flohr–Mikenas Attack.

ECO
The Encyclopaedia of Chess Openings has classified the English Opening under the codes A10 through A39:
 * A10 1.c4
 * A11 1.c4 c6 (Caro-Kann Defensive System)
 * A12 1.c4 c6 2.Nf3 d5 3.b3 (Also the Bogoljubov Variation of the Anglo-Slav Variation of the Réti Opening)
 * A13 1.c4 e6 (Agincourt Defense)
 * A14 1.c4 e6 2.Nf3 d5 3.g3 Nf6 4.Bg2 Be7 5.0-0 (Neo-Catalan Declined Line in the Agincourt Defense)
 * A15 1.c4 Nf6 (Anglo-Indian Defense)
 * A16 1.c4 Nf6 2.Nc3 (Queen’s Knight Variation of the Anglo-Indian Defense)
 * A17 1.c4 Nf6 2.Nc3 e6 (Hedgehog System of the Queen’s Knight Variation of the Anglo-Indian Defense)
 * A18 1.c4 Nf6 2.Nc3 e6 3.e4 (Mikenas–Carls Variation)
 * A19 1.c4 Nf6 2.Nc3 e6 3.e4 c5 (Sicilian Variation of the Mikenas-Carls Variation)
 * A20 1.c4 e5 (King’s English Variation)
 * A21 1.c4 e5 2.Nc3 (Reversed Sicilian)
 * A22 1.c4 e5 2.Nc3 Nf6 (Two Knights Variation of the King’s English)
 * A23 1.c4 e5 2.Nc3 Nf6 3.g3 c6 (Bremen System, Keres Variation)
 * A24 1.c4 e5 2.Nc3 Nf6 3.g3 g6 (Bremen System with ...g6) (also known as the Fianchetto Line)
 * A25 1.c4 e5 2.Nc3 Nc6 (Reversed Closed Sicilian)
 * A26 1.c4 e5 2.Nc3 Nc6 3.g3 g6 4.Bg2 Bg7 5.d3 d6 (Full Symmetry Line in the Closed System)
 * A27 1.c4 e5 2.Nc3 Nc6 3.Nf3 (Three Knights System)
 * A28 1.c4 e5 2.Nc3 Nc6 3.Nf3 Nf6 (Four Knights Variation)
 * A29 1.c4 e5 2.Nc3 Nc6 3.Nf3 Nf6 4.g3 (Four Knights, Kingside Fianchetto)
 * A30 1.c4 c5 (Symmetrical Variation)
 * A31 1.c4 c5 2.Nf3 Nf6 3.d4 (Symmetrical, Benoni Formation) (also known as the Anti-Benoni Variation)
 * A32 1.c4 c5 2.Nf3 Nf6 3.d4 cxd4 4.Nxd4 e6 (Spielmann Defense of the Anti-Benoni Variation of the Symmetrical)
 * A33 1.c4 c5 2.Nf3 Nf6 3.d4 cxd4 4.Nxd4 e6 5.Nc3 Nc6
 * A34 1.c4 c5 2.Nc3 (Normal Variation of the Symmetrical)
 * A35 1.c4 c5 2.Nc3 Nc6 (Two Knights Variation of the Symmetrical)
 * A36 1.c4 c5 2.Nc3 Nc6 3.g3 (Fianchetto Variation of the Symmetrical)
 * A37 1.c4 c5 2.Nc3 Nc6 3.g3 g6 4.Bg2 Bg7 5.Nf3 (Two Knights Line)
 * A38 1.c4 c5 2.Nc3 Nc6 3.g3 g6 4.Bg2 Bg7 5.Nf3 Nf6 (Full Symmetry Line)
 * A39 1.c4 c5 2.Nc3 Nc6 3.g3 g6 4.Bg2 Bg7 5.Nf3 Nf6 6.0-0 0-0 7.d4 (Mecking Variation)

Depiction in cinema
The English Opening is used by Professor Moriarty in the film Sherlock Holmes: A Game of Shadows as he and Holmes discuss their competing plans over a game of chess. Both Holmes and Moriarty eventually play the final moves blindfolded by citing out the last moves in descriptive notation (rather than algebraic, as the former was contemporary in the late 19th century), ending in Holmes checkmating Moriarty, just as Watson foils Moriarty's plans.

1.c4 is also used in Pawn Sacrifice by Bobby Fischer in the climactic game six of the 1972 World Chess Championship versus Boris Spassky.

title: English Opening


text:
California Academy of Sciences

The California Academy of Sciences is a research institute and natural history museum in San Francisco, California, that is among the largest museums of natural history in the world, housing over 46 million specimens. The academy began in 1853 as a learned society and still carries out a large amount of original research. The institution is located at the Golden Gate Park in San Francisco.

Completely rebuilt in 2008, the academy's primary building in Golden Gate Park covers 400000 ft2. In early 2020, before the COVID-19 pandemic, the California Academy of Sciences had around 500 employees and an annual revenue of about $33 million.

The museum is accessible via public transit on the N Judah Metro line. The westbound 9th Avenue and Irving station is located about 0.5 miles from the Academy of Sciences. Three Muni bus lines also serve the museum, including the 44, 5, and 7 lines.

Governance
The California Academy of Sciences, California's oldest operating museum and research institution for the natural sciences, is governed by a 41-member board of trustees who are nominated and chosen by the California Academy of Sciences Fellows. The Academy Fellows are, in turn, "[n]ominated by their colleagues and appointed by the Board of Trustees...the Fellows remain members of the Fellowship for life." The board of trustees are then responsible for appointing the executive management of the academy, who in turn are responsible for overseeing the academy's overall operation and the hiring of its other managers and employees.

Institute for Biodiversity Science and Sustainability (IBSS)
Besides its function as source of public science education through its museum, the California Academy of Sciences also operates the Institute for Biodiversity Science and Sustainability (IBSS) as its research arm, conducting research in the fields of taxonomy, phylogenetics, and biodiversity studies. Although one aspect of the IBSS is available for view by museum patrons at the science "project lab" exhibit, most of the research happens in laboratories and facilities "behind the scenes" and not observable by the public. In fact, unbeknownst to most patrons, research and administrative facilities occupy nearly 50% of the Academy's physical structure.

Exhibits
The main thrust of the exhibits is natural history. The venues of the museum include the following:
 * Kimball Natural History Museum – generally encompasses the entire museum outside the planetarium, rainforest, and aquarium, and includes Africa Hall (the Academy's oldest running exhibit), the East Wing (which includes a Foucault pendulum, also a carry-over exhibit from the older, pre-2008 renovation of the Academy), the West Wing (which housed several geophysical exhibits), as well as several smaller exhibits distributed throughout the remainder of the Academy building.
 * Morrison Planetarium – features a digitally controlled planetarium dome measuring 90 ft in diameter with a 75 ft diameter screen.
 * Rainforests of the World – rainforest exhibit enclosed in a 90 ft glass dome.
 * Steinhart Aquarium – includes exhibits of coral reefs, tide pools, and swamp habitats.
 * Penguin Habitat – features a colony of African penguins.

Besides its museum programs, the California Academy of Sciences offers many educational and community outreach programs to members of the public at large.

Research
Academy scientists, under the Academy's Institute for Biodiversity Science and Sustainability, conduct systematic and conservation research in several different fields, including anthropology, marine biology, botany, entomology, herpetology, ichthyology, invertebrate zoology, mammalogy, ornithology, geology, and paleontology. There also is a strong emphasis on environmental concerns, with all the various departments collaborating closely to focus on systematic biology and biodiversity. Academy researchers study life around the world: a 2011 expedition to the Philippines discovered an estimated 300 species new to science. The Academy publishes the peer-reviewed journal Proceedings of the California Academy of Sciences, as well as Occasional Papers, Memoirs, and Special Publications.

Early years
The California Academy of Natural Sciences was founded in 1853, only three years after California joined the United States, becoming the first society of its kind in the Western US. Its stated aim was to undertake "a thorough systematic survey of every portion of the State and the collection of a cabinet of her rare and rich productions." It was renamed as the more inclusive California Academy of Sciences in 1868.

The academy had a forward-thinking view towards women in science, passing a resolution in its first year of existence that the members "highly approve of the aid of females in every department of natural science, and invite their cooperation." This policy led to several women being hired into professional positions as botanists, entomologists, and other occupations during the 19th century, when opportunities for women in the sciences were limited, and often, those that existed were restricted to menial cataloging and calculation work. In 1892, Alice Eastwood, a botanist, was hired by the academy and worked there until she retired in 1949. She created the collection of rare plants, which was saved when the academy was destroyed in the 1906 San Francisco earthquake

The academy's first official museum opened in 1874 at the corner of California and Dupont Streets (now Grant Avenue) in what is now Chinatown, and drew up to 80,000 visitors a year. To accommodate its increasing popularity, the academy moved to a new and larger building on Market Street in 1891, funded by the legacy of James Lick, a 19th-century San Francisco real estate mogul, entrepreneur, and philanthropist.

However, only fifteen years later, the Market Street facility fell victim to the 1906 San Francisco earthquake and three days of fire, which also wiped out all but a wheelbarrow full of the academy's library and specimen collections. In the widespread destruction occurring in the aftermath of the quake, academy curators and staffers only were able to retrieve a single cart of materials, including academy minute books, membership records, and 2,000 type specimens. The 1905-1906 scientific collecting expedition to the Galápagos Islands (the first of several sponsored by the academy to the archipelago) already was underway, and it returned seven months later, providing replacement collections for those lost.

Golden Gate Park site
In 1916, the Academy moved to the North American Hall of Birds and Mammals in Golden Gate Park, the first building on the site that was to become its permanent home. In 1923, the Steinhart Aquarium was added, followed in 1934 by the Simson African Hall.

During World War II, the Academy contributed to the American war effort by using its workshop facilities to repair optical and navigational equipment for United States Navy ships; San Francisco was a major port for the Pacific War arena.

The post-war years saw a flurry of new construction on the site; the Science Hall was added in 1951, followed by the Morrison Planetarium in 1952. The Morrison Planetarium was the seventh major planetarium to open in the United States and featured a one-of-a-kind star projector, built by Academy staff members (in part using the expertise gained doing the optical work for the US Navy during World War II). The Academy Projector projected irregularly shaped stars, rather than the circular stars projected by many optical star projectors. The irregular shapes were created by placing variously sized grains of silicon carbide onto the glass star plates by hand, then aluminizing the plates, and brushing away the silicon carbide grains.

In 1959, the Malliard Library, Eastwood Hall of Botany, and Livermore Room all were added. Throughout the 1960s, universities concentrating on the new field of molecular biology divested themselves of their traditional specimen collections, entrusting them to the academy and leading to a rapid growth of the Academy's holdings.

In 1969, another new building, Cowell Hall, was added to the site. In 1976, several new galleries were opened, and the following year, in 1977, the "fish roundabout" was constructed.

Prior to the old building being torn down in 2005, there was a Life through Time gallery, housing a large display on evolution and paleontology. There was a Gem and Mineral Hall, a section on Earthquakes, and a Gary Larson exhibit.

Earthquake damage and new building
The academy buildings were damaged significantly in the 1989 Loma Prieta earthquake. Subsequently, the Bird Hall building was closed to ensure public safety. The inadequately engineered Steinhart Aquarium suffered dramatic seismic damage from the 1989 earthquake, as well.

As plans were made to repair the damage and make the buildings seismically stable, it was realized that a considerable amount of work would be needed to bring the buildings up to modern standards. This led to the idea of giving the academy a complete overhaul, thus motivating the closing of the main site.

Construction began on the new $500 million building on September 12, 2005, while the exhibits were moved to 875 Howard Street for a temporary museum.

The academy reopened with a free day on September 27, 2008. For most of the day the line for admittance was over a mile (nearly two kilometers) long, and although over 15,000 people were admitted, several thousands more had to be turned away.

In May 2020, during the COVID-19 pandemic, the Academy announced that it would lay off 105 of its then 504 employees, furlough 96 others, and enact pay cuts among part of the rest. Due to the COVID-19 lockdown's effect on ticket sales, the organization was expecting its revenue to decrease by around $12 million (36%) in the next fiscal year.

Environmental design of new building

The design architect for the museum replacement project was Renzo Piano. His design was awarded the Urban Land Institute (ULI) Award for Excellence for the Americas region in 2008, as well as the Holcim Award Silver for sustainable construction projects in the North America region in 2005. One critic praised the building as a "blazingly uncynical embrace of the Enlightenment values of truth and reason", and a "comforting reminder of the civilizing function of great art in a barbaric age".

The new building emphasizes environmentally friendly design, in keeping with the academy's focus on ecological concerns and environmental sustainability. It received Platinum certification under the LEED program. This project was featured on the Discovery Channel Extreme Engineering series in 2006, the National Geographic Channel Man-Made series in July 2008, and Smithsonian Channel's How Do They Build That? in August 2022.

The new building includes an array of environmentally friendly features:
 * Produces 50 percent less waste water than previously
 * Recycles rainwater for irrigation
 * Uses 60,000 photovoltaic cells
 * Supports a green roof with an area of 2.5 acre
 * Uses natural lighting in 90 percent of occupied spaces
 * Was constructed of over 20000 cuyd of recycled concrete
 * Construction includes 11 million pounds (5,000 t) of recycled steel
 * Wall insulation made from scraps of recycled denim

Green roof
The California Academy of Science green roof has several environmentally friendly features, as well as sustainable design. Renzo Piano was inspired by seven major hills of San Francisco, which typically refers to: Telegraph Hill, Nob Hill, Russian Hill, Rincon Hill, Mount Sutro, Twin Peaks and Mount Davidson. The living green roof was planted with 1.7 million California native plants. The museum's central piazza lies beneath a massive glass ceiling in the roof, which opens to allow cool night air to flow into the building below; by using this kind of natural ventilation instead of air conditioning to regulate interior temperature, the building becomes more energy efficient. Renzo Piano and SWA Group won the American Society of Landscape Architects (ASLA) Award in design in 2009.

title: California Academy of Sciences


text:
Shinden

Shinden may refer to:
 * Kyushu J7W Shinden, an interceptor airplane
 * Shinden (寝殿), the main building of a shinden-zukuri, a Heian period mansion in Japan
 * Shinden (神殿), or honden, the most sacred part of a Shinto shrine
 * Shinden Station (disambiguation), several train stations

title: Shinden


text:
Talk:Transfermium Wars

"Seaborg proved that it was a misreading" is a strong statement especially taking into account that he had a conflict of interests. Apparently IUPAC has a different view. Any references?

I changed "proved" -> "claimed" since nobody came with a reference.

The pages for elements 111 through 115 all link here, but this page has no mention of them. What's the deal with them? (I hope they keep their current names. The atomic symbol for Unununium is Uuu. How cool is that?) -Branddobbe 07:54, Apr 15, 2004 (UTC)
 * Yep, it makes no sense. The links should have been to Systematic element name instead, which has the link to this page. Jay 10:44, 15 Apr 2004 (UTC)

There is additional prose that could be used for improvement of this article at Talk:Transfermium Wars/Dubnium should anyone seek to improve the article.

Germans?
The introduction lists the German group as being involved in the dispute, but the text of the article provides no follow up. The article should either be expanded to support their inclusion, or they should be removed. Gentgeen 07:47, 21 January 2006 (UTC)

"Discovery"
Someone should probably mention that none of the elements in question were discovered in the conventional sense, other than attempting to synthesise the element, and then looking for it to make sure that it was in fact created.

Handing out autographed periodic tables
Sorry if I'm just being ignorant, but is "Glenn T. Seaborg was still alive and handing out autographed periodic tables" actually true and worth mentioning? It sounds like someone was trying to be funny. But if I'm wrong, I apologise. 213.107.97.72 16:15, 25 April 2007 (UTC)

 * It certains IS funny though. Michael.A.Anthony 22:54, 20 September 2007 (UTC)

It's now officially three years since that edit was made, and nobody's changed it. Wow. Haemorrhage 16:37, 16 November 2007 (UTC)

Be bold? I'll fix it. Dreamyshade (talk) 06:04, 24 December 2007 (UTC)

Links to wrong elements
I think the edits of Jan.17 (2008) indicated a valid problem - where to link element names which now refer to other elements? For example it is confusing to link IUPAC's "Dubnium" for element 104 to the article on Dubnium which describes element 105. This may be why User 64.246.250.3 linked "Dubnium" for 104 to Rutherfordium which is the current name for 104. This was consistent with the links for the Dubna and Darmstadt proposals, but is confusing here as Rutherfordium is now used for 106, which may be why User Dreamyshade reverted the changes and described them as "sneakiness". (Assume good faith whenever some argument can be made for an edit).

I propose another solution to this problem: remove the links for all the preliminary element names, and retain links only for the final 1997 proposal which corresponds to the current names. Dirac66 (talk) 15:13, 18 January 2008 (UTC) Slightly revised. Dirac66 (talk) 15:31, 18 January 2008 (UTC)

Haha, sorry. I didn't see any other edit history for that IP, and I'm not an expert in this. :) Maybe it's not the best article for me to be watching... Dreamyshade (talk) 20:45, 18 January 2008 (UTC)

GSI
Was there any controversy of the discovery of elements 107 to 109 by the German group? I thought the controversy was only about elements 104 and 105. --Roentgenium111 (talk) 22:24, 18 May 2009 (UTC)

Order of sections (controversy first)
In the current version of the article, the controversy section appears before the list of proposals. As a result, this section is unclear because the necessary context is missing: "The American name to 106 was also objectionable to some because Glenn T. Seaborg was still alive." At this point in the article, the name Seaborg was not yet mentioned, and thus this statement comes out of the blue.

I see two solutions:
 * Re-order the sections, so that controversy comes later.
 * Add some more context to the controversy section

Patrickdepinguin (talk) 07:13, 11 June 2009 (UTC)

I have followed your second solution by specifying that the American name for 106 is seaborgium in order to indicate the relevance of Seaborg. Dirac66 (talk) 14:11, 11 June 2009 (UTC)

Introduction talks about 104-106, resolution about 104-109
The introduction line "The names for the chemical elements 104 to 106 were the subject of a major controversy starting in the 1960s which was finally resolved in 1997." does not match what is written in the resolution section. The introduction talks about 3 elements, while the resolution is about 6. I believe the introduction should be edited... Patrickdepinguin (talk) 07:15, 11 June 2009 (UTC)

I have changed the introduction to line to read 104 to 108. The controversy did start with 104-106, but there was indeed later disagreement about 107-108 as explained further in the article. For 109 however, there was never any disagreement even though it was added on to the final resolution. Dirac66 (talk) 14:11, 11 June 2009 (UTC)

 * IMO the introduction did match the article. The element 108 was dragged into the controversy by the commission, but the major controversy was on elements 104-106, because they were the only ones whose discoverer was unclear. Also for element 107, the slight deviation of the IUPAC from the suggested name was not a "controversy" - there is no evidence that the GSI disagreed with it. Maybe we should split the introduction in two sentences to reflect this? --Roentgenium111 (talk) 15:02, 11 June 2009 (UTC)

 * OK, what do you think of the following introduction? "The names for the chemical elements 104 to 106 were the subject of a major controversy starting in the 1960s. The final resolution of this controversy in 1997 also decided the names of elements 107 to 109." This would mention all 6 elements to be discussed at the beginning. Dirac66 (talk) 16:09, 11 June 2009 (UTC)
 * Very good. Go ahead! --Roentgenium111 (talk) 16:43, 11 June 2009 (UTC)

Systematic numerical names
I think that the article has been improved by the recent changes, many by Roentgenium111. However one point which is still absent is the first (pre-1994?) IUPAC proposal for the temporary use of "systematic" names such as unnilquadium for 104 etc. The See also section does have a link to Systematic element names, but there is no mention (in that article or in this one) of why the systematic names were proposed. As I remember it, the systematic names were proposed by IUPAC as a temporary solution in order to avoid taking sides in the American-Russian controversy described here. When they proved unpopular, IUPAC proposed its 1994 solution for 104-109 and reserved numerical names for still newer or undiscovered elements. So I think these names were part of the controversy and should be mentioned - does anyone have sources so we can get the details right? Dirac66 (talk) 20:31, 12 June 2009 (UTC)

 * Since the Element Atomic Number is a much more important piece of information than the "honorary?" element name given by IUPAC to the discovered element, The individual squabbles re this matter are not really scientifically significant. However, the format of organization of these atomic numbers and names into a modern information chart is. It is hoped that a consideration of the organization of the method of organizing and presenting the data on atomic numbers 119 and 120 will include a consideration as to whether these two elements represent the start of a new series, per the IUPAC standard table, or else the last two elements of the previous series, as per the Janet Periodic Table.WFPM (talk) 16:41, 15 August 2010 (UTC) See Charles Janet

American objection to "Kurchatovium"
Is there a citation for the note that the Americans objected to naming element 104 after Kurchatov because of his role in the Soviet atomic bomb development? It sounds logical, but I'm unable to find anything to back it up. I'm wondering if it needs a citation to contrast this with the naming of other elements after nuclear physicists.216.17.31.166 (talk) 17:41, 18 October 2017 (UTC)
 * Actually, one suggested compromise (coming directly from Seaborg and addressed to the TWG group) was to name element 106 kurchatovium to honour the Dubna team if the Americans got credit for elements 104 and 105: this episode is mentioned at seaborgium and is cited. This was later dropped from consideration due to their disagreements with the TWG report. Double sharp (talk) 10:00, 10 April 2018 (UTC)

Orphaned references in Transfermium Wars
I check pages listed in Category:Pages with incorrect ref formatting to try to fix reference errors. One of the things I do is look for content for orphaned references in wikilinked articles. I have found content for some of Transfermium Wars's orphans, the problem is that I found more than one version. I can't determine which (if any) is correct for this article, so I am asking for a sentient editor to look it over and copy the correct ref content into this article.

Reference named "Haire": From Naming of chemical elements:  From Nobelium:

I apologize if any of the above are effectively identical; I am just a simple computer program, so I can't determine whether minor differences are significant or not. AnomieBOT ⚡ 19:40, 14 August 2018 (UTC)

title: Talk:Transfermium Wars


text:
694 BC

The year 694 BC was a year of the pre-Julian Roman calendar. In the Roman Empire, it was known as year 60 Ab urbe condita . The denomination 694 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

Events and trends

 * Duke Xiang of Qi and Duke Huan of Lu met at Luo(濼). Duke Huan of Lu and his wife, Wen Jiang went to Qi.
 * Duke Huan of Lu died in Qi, and Qi killed Prince Peng Sheng(彭生), who was in Duke's car.
 * Troops of Qi killed Zheng-zi Wei(7th ruler of Zheng) and Gao Qumi(高渠弥).Ji Zhong(祭仲) invited Zheng-zi Ying(8th ruler of Zheng) from Chen and helped him assume the throne.
 * Duke Hei Jian(黒肩) of Zhou killed King Zhuang of Zhou and plotted to help Prince Ke(克) assume the throne. Xin Bo(辛伯) reported it to King Zhuang, and killed Duke Hei Jian. prince Ke defected to Yan.

Deaths

 * Ashur-nadin-shumi, Assyrian king of Babylon
 * Duke Huan of Lu, ruler of the state of Lu
 * Luli, king of Tyre

title: 694 BC


text:
Genoa (sail)

A genoa sail is a type of large jib or staysail that extends past the mast and so overlaps the main sail when viewed from the side, sometimes eliminating it. It was originally called an "overlapping jib" and later a genoa jib. It is used on single-masted sloops and twin-masted boats such as yawls and ketches. Its larger surface area increases the speed of the craft in light to moderate winds; in high wind, a smaller jib is usually substituted, and downwind a spinnaker may be used.

Definition
The term jib is the generic term for any of an assortment of headsails. The term genoa (or genny) refers to a type of jib that is larger than 100% of the foretriangle, which is the triangular area formed by the point at which the stay intersects the mast, and deck or bowsprit, and the line where the mast intersects deck at the rail. Colloquially the term is sometimes used interchangeably with jib. A working jib is no larger than 100% of the foretriangle. A genoa is larger, with the leech going past the mast and overlapping the mainsail. To maximize sail area, the foot of the sail is generally parallel and very close to the deck when close hauled.

Genoas are categorized by a percentage representing their area relative to 100% of the foretriangle. Sail racing classes often specify a limit to genoa size. Genoas are classified by their size; a modern number 1 genoa would typically be approximately 155%, but historically number 1 genoas have been as large as 180%. Number 2 genoas are generally in the range of 125–140%. Working jibs are also defined by the same measure, typically 100% or less of the foretriangle. Under Performance Handicap Racing Fleet rules, most boats are allowed 155% genoas without a penalty.

Handling issues
Maximizing the sail area can cause more difficult handling. It may be harder to tack a genoa than a jib, since the overlapping area can become fouled among the shrouds and/or mast unless carefully tended during the tack. Genoas are very popular in some racing classes, since they count only the foretriangle area when calculating foresail size; a genoa allows a significant increase in actual sail area within the calculated sail area. In boats where sail restrictions do not apply, genoas of 180% overlap can be found, although those over 150% are rare because the additional area is shadowed by the mainsail when close hauled and generates diminishing returns in terms of power per actual sail area.

The gennaker
The gennaker has been around for several decades now, and as the name suggests, it is a hybrid between a genoa and a symmetrical spinnaker. A brand name of North Sails, the gennaker started as a cruising sail based on the Code 0 spinnakers used on racing boats. Gennakers and similar code 0 variants offered by other makers are even larger than genoas (200% overlaps are not uncommon), and they have a much greater camber for generating larger amounts of lift when reaching. Flat-cut gennakers can be effective for angles as low as 60–70 degrees. Spinnakers perform much better when running because the main sail blocks the wind of gennaker above 135–150 degrees.

History
The famous Swedish sailor and shipowner Sven Salén (1890–1969) first used the genoa on his 6 m R-yacht May-Be by the 1926 in Coppa del Tirreno in Genoa, hence the name. He successfully used it during the Scandinavian Gold Cup's races of 1927 in Oyster Bay (US). Sven Salén also pioneered the parachute spinnacre.

A similar type of jib was in use for centuries by the fishermen in the Netherlands with their Botter type ships. The fishermen relied on the combination of a large jib while fishing so the mainsail could remain unused. After fishing the fisherman's jib helped to get the fish to markets fast.

A correct explanation of the interaction between jib and mainsail was published by aerodynamicist and yachtsman Arvel Gentry in 1981, and "is much more complicated than the old theories imply". This states that the widely believed explanation of the slot effect is "completely wrong" and shows that this is not due to the venturi effect (or "valve effect" to use Curry's term) accelerating the air in the slot. Instead it is shown that the air in the slot is slowed and its pressure increased reducing the tendency of the mainsail to stall, that the mainsail reduces the air pressure on the lee side of the jib accelerating that airflow, and that the mainsail increases the angle at which the air meets the luff of the jib, allowing the boat to point higher. Gentry points out that proper understanding of sail interaction allows better sail trimming.

title: Genoa (sail)