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Cosmic Encounter

Cosmic Encounter is a science fiction–themed strategy board game designed by "Future Pastimes" (collectively, Peter Olotka, Jack Kittredge and Bill Eberle, with Bill Norton) and originally published by Eon Games in 1977. In it, each player takes the role of a particular alien species, each with a unique power to bend or break one of the rules of the game, trying to establish control over the universe. The game was inducted into the Academy of Adventure Gaming Arts & Design Adventure Gaming Hall of Fame in 1997.

Cosmic Encounter is a dynamic and social game, with players being encouraged to interact, argue, form alliances, make deals, double-cross, and occasionally work together to protect the common good. Most editions of the game are designed for three to five players, although official rules exist for playing with as many as eight players.

Basic rules
Cosmic Encounter is based on a fixed set of rules which are subsequently modified by other elements of the game.

Each player begins with a color-coded "home system" containing five planets, and twenty ships (formerly referred to as "tokens") representing starships that populate these planets as "colonies" (formerly known as "bases"). A central "warp" is used to place defeated ships for all players. The object of the game is to establish colonies on five planets outside one's home system. Each player is dealt a hand of cards from the "cosmic deck," which includes several types of cards: Attack cards with numbered values, Negotiate (formerly Compromise) cards, Reinforcement cards, and Artifact (formerly Edict) cards.

The turn player is referred to as the "offense." On a player's turn, they retrieve one ship from the warp, and then draw a card from the "Destiny" deck, containing color-coded cards which indicate which player they must have an encounter with; that player becomes the "defense." Using a special "hyperspace gate" (formerly "hyperspace cone" or simply "cone") indicator, the offense selects the planet at which the encounter will take place, and then places 1 to 4 of their ships on the gate; the defense simply defends with however many ships they have on the targeted planet. Both the offense and defense can then ask the other players individually to ally with their side; each invited player may commit up to 4 ships to either side of the conflict.

Once allies have committed, the offense and defense both select encounter cards from their hands to place face-down, then reveal them and play out the encounter based on the types of cards they used.
 * If players use Attack cards, the total of the card's value and number of allied ships are added for both sides, and the side with the larger value wins, with the defending player winning in case of ties. All players involved in the encounter may play Reinforcement cards from their hands to add numerical bonuses to each side's forces. If the offense's side wins, the defense's colony is lost and all ships on the defense's side are sent to the warp, and the offense and their allies land their ships on that planet, establishing new colonies on it (or adding more ships to existing colonies there, if they already had colonies there). If the defense's side wins, all ships on the offense's side are sent to the warp, and defensive allies gain a reward of either a ship from the warp or a new card drawn from the deck for each of their ships that they sent to help defend.
 * If both players use Negotiate cards, they have one minute to make a deal, such as exchanging colonies or cards from their hands, while all allies are sent back to their owners' colonies (allies get nothing in this situation). If a deal can't be made, both players lose three ships each as a penalty.
 * If one players plays a Negotiate card and the other plays an Attack card, the player who played the Negotiate card immediately loses, but they get "compensation" from the victor by drawing cards from the victor's hand equal to the number of ships they lost in the battle. Allies on the Negotiate player's side do not get anything.

At the end of the offense's turn, they may have a second encounter if they won an attack or made a deal. If they can't, choose not to, or have already had two encounters this turn, then play proceeds to the next player.

Alien powers
The rules become more complex with the introduction of alien powers. These are typically drawn randomly at the start of the game and known to all players; however, variants exist where players can select their powers, use multiple powers simultaneously, or hide their powers until they are used. Each power gives the player a way to bend the core rules to their advantages, typically in one of the following ways: A player's alien power is only active if they have three or more colonies in their home system, and if lost, can be regained by taking back a third colony.
 * Continuous effects, such as the Macron, where each of its ships is valued as 4 instead of 1 during combat
 * Combat resolution effects, such as the Void, where any ship that loses against it is removed from the game entirely instead of going to the warp
 * Victory condition changes, such as Masochist, who wins if it loses all its ships
 * Role-playing elements, such as the Sniveler, who, if in a losing position, may whine to the other players to gain benefits

The current edition of Cosmic Encounter, published by Fantasy Flight Games, includes a total of 238 aliens across all of its expansion and promo sets. In addition, many players have created their own "homemade" powers, and have posted these along with other various game extensions on the Internet.

Variants
More advanced optional game components can add further levels of complexity and unpredictability. Various editions have included varying numbers of these optional components. They include:
 * Flares: Cards that grant a limited version of an alien power, or, if used by the player who possesses that power, a significant boost to their own power.
 * Lux (formerly Lucre): In-game currency that allows more control of resources (such as buying more cards for one's hand or ships back from the warp).
 * Moons: Special tokens which may be occupied by players, doing so grants one access to its special ability. Moon abilities can be powerful (such as retaining an alien power when it would normally be lost), while others are best described as "silly" (such as forcing the owner to speak in rhyme).
 * Special planetary systems: Added in an expansion to the Eon Productions version of Cosmic Encounter and kept in the Mayfair version, the special systems have additional rules in regards to the player's initial setup, colonies, and victory conditions.
 * Technologies: An array of boosts and special abilities, which must be researched (by placing ships on them) for several turns before they can be put into play. The power of technology cards varies wildly, with more powerful technologies requiring more turns to research. For example, the Xenon Lasers tech costs two ships, and its owner may change encounter totals by one point, while the Omega Missile tech costs eight ships, and destroys a planet.
 * Rewards: A deck of powerful cards that can only be drawn by victorious defensive allies. Reward cards include "kickers," multipliers for encounter cards, and "rifts," booby traps that free ships from the warp, or send ships there if they are ever taken from another player's hand.
 * Large group games: Official variants include rules and cards for adding a seventh or eighth player. However, with unofficial variants, the game can support as many players as the number of available player colors. With all expansions, the Mayfair Games edition has ten player colors for a ten-player game and Fantasy Flight Games' edition has eight player colors for an eight-player game, or up to 13 player colors if the translucent plastic ships from the 42nd Anniversary Edition are each included as their own color.

History
The original version of Cosmic Encounter had exactly six alien powers and was designed for up to six players. This edition was nearly published by Parker Brothers in the mid-1970s; when it was not, the designers founded Eon Productions, Inc. to publish it.

The first Eon edition was released in 1977. It allowed up to four players and included fifteen alien powers. Over the next five years, Eon released nine expansions, adding sixty more alien powers, components for a fifth and sixth player, and several new types of pieces, including "Flare" cards, money (Lucre), Moons, and special power planet systems. The artwork on these early editions included images painted by Dean Morrissey. Eon published three versions of the base game, differing only in box size and cover art.

In 1986, the game was republished in the U.S. by West End Games. The game used the same deck of cards and number of players, and the same powers with five additional powers from Eon expansion sets #1 and #2. However, the cards and tokens were incompatible with the Eon edition. Meanwhile, in the UK, the game was published by Games Workshop. The GW edition supported six players, with powers from the Eon base set and some of the first three expansions.

In 1991, the game was licensed by Mayfair Games. Mayfair published Cosmic Encounter, an expansion called More Cosmic Encounter (1992), and a stripped-down introductory version of the game called Simply Cosmic (1995). The Mayfair edition revised some powers from the original Eon set, introduced many more, and significantly revised some of the existing components. It also introduced several new components. By combining the three Mayfair products, it is possible to play a 10-player game.

In 2000, Avalon Hill (by then a division of Hasbro) published a simplified version in one box with plastic pieces. While the production quality was high, this version was limited to 20 powers and four players and received no expansions.

On August 17, 2007, Fantasy Flight Games announced plans to reprint the game in 2008. Game designer Kevin Wilson gave demonstrations of Fantasy Flight's Cosmic Encounter version at Gen Con 2008, and the game was released in December. This edition included 50 aliens, flare cards, a new Technology variant, and support for 5 players. Since 2008, Fantasy Flight has released seven expansion sets:

Each set of aliens includes those aliens' alien sheets and flare cards, along with any special tokens certain aliens may need. An extra player includes 20 ships, 5 planets, a colony marker, and destiny cards of the corresponding color.

In 2018, a special 42nd-anniversary edition was released by Fantasy Flight, with new box art, translucent ships, a new alien (the Demon), and a few other minor features. The new edition is still compatible with Fantasy Flight's expansions.

In 2022, Fantasy Flight published the seventh expansion for the game: Cosmic Odyssey, designed by Jack Reda, which adds a campaign mode, expands on variant from the previous expansions, and includes several new variants (some of which are reimagined versions of variants from previous editions).

A standalone two-player adaptation of the game was released in 2020. Titled Cosmic Encounter Duel, it still features a race to colonize five planets through attacks and negotiations. However, it replaces the standard game's multiplayer alliance system with virtual allies called Envoys, and increases the degree of hidden information in an encounter through methods such as giving the players rotating dials with which to secretly choose their fleet strengths.

Online version
In 2003, original designer Peter Olotka and partners launched a new version called Cosmic Encounter Online that could be played over the internet. , this version had 35 powers, including four new aliens and two more that were designed for online play (such as Dork, which blocks other players' screens).

Cosmic Encounter Online has since been shut down. It has been superseded by Cosmic Encounter Connector, released in 2015 and available through Tabletop Simulator.

First Eon edition (1977) and subsequent expansion sets (1978–1982)
In the May 1978 edition of Dragon (Issue 14), Tony Watson found the game to be "highly playable, fanciful, and very fun." Watson liked the professional quality of the game components, and admired the complex player strategies that were not immediately apparent upon reading the rules. He concluded, "Cosmic Encounter is a new type of SF game... and it hits it mark quite squarely. From both a physical and design point of view it is a very good game."

In the June–July 1978 edition of White Dwarf (Issue 7), Fred Hemmings found the game "simple to learn, and yet at the same time is so full of good ideas and potential player skill." Hemmings admired the "beautifully produced" game components, but wished that there was more than one winning objective — although he did note that using the two available expansions resulted in 35 alien races to choose from, giving a potential for more than a million combinations. He gave the game an overall rating of 8 out of 10, saying, "What makes this game is the aliens —they vary from good to excellent, and so does the game."

In the September 1978 edition of Dragon (Issue 18), Dave Minch questioned the science fiction angle of Cosmic Encounter, saying it was "nothing more than hype." When Minch delved below the SF "patina", he found a game that "combines several elements of classic, abstract games. There are cards which introduce both chance and strategy of play, as in poker or bridge. There are chips representing the bases which you must build to win the game, giving the positional and matching requirements of pit-and-pebble games, as well as a betting flavor like poker." Minch concluded with a recommendation, saying, "This is a simple game both to learn and to play. Best of all, it’s fun and pretty much open-ended."

In the inaugural edition of Ares Magazine (March 1980), Greg Costikyan rated the game 9 out of 9, saying, "The result is a weird, constantly mutating, and gripping game that does not lose its appeal even after innumerable playings. The addition of any of the four expansion sets makes Cosmic Encounter even more fascinating."

In the March 1981 edition of The Space Gamer (No. 37) Steve Jackson gave a thumbs up, saying, "I like Cosmic Encounter. It's totally original, and a lot of fun. I recommend it without reservation to gamers".

In the October 1981 edition of The Space Gamer (No. 44), Forrest Johnson thought the continued publication of expansion sets (six to that point in time) was perhaps an indication that the game was losing replay value: "Expansion sets 1 and 2 would be more valuable to a new player; Eon Products is approaching the point of diminishing returns. But sets 6 and 7 still have a lot of value for CE enthusiasts."

West End Games and Games Workshop editions (1986)
In the March 1986 edition of White Dwarf (Issue 75), Tim Wilson gave the re-issued game an overall rating of 8 out of 10, saying, "Cosmic Encounter is an easy, light-hearted game with plenty of scope for devious strategy and backstabbing... The earlier version of this game [published by Eon] proved too scarce and expensive for it to become well-known: try it now, and see why it was worth re-releasing."

Mayfair Games edition (1991) and subsequent expansion set (1993)
In the November 1991 edition of Dragon (Issue 175), Allen Varney gave an ebullient review, saying, "This brilliantly interactive and spectacularly fun 1977 design is my very favorite game, bar none." Varney questioned the high price of the Mayfair Games re-issue, but concluded, "You definitely will get $35 of fun out of this box. I’ve played the original Cosmic Encounter game (from the late Eon Products) over a hundred times; every game was wildly different."

Varney again gave a very positive review of the Mayfair edition in the December 1993 edition of Dragon (Issue 200), but questioned some of the new rules in Mayfair's expansion set, saying the set "offers many terrific powers (and some terribly unbalanced ones) plus new cards and forgettable rules additions like Lucre and Moons."

In 1992, a new edition of Cosmic Encounter won the Origins Award for Best Fantasy or Science Fiction Boardgame of 1991 and placed 6th in the Deutscher Spiele Preis.

Retrospective
Cosmic Encounter was chosen for inclusion in the 2007 book Hobby Games: The 100 Best. Bruno Faidutti commented, "The box for Eon's first edition of Cosmic Encounter proclaimed 'the science-fiction game for everyone.' And, indeed, long before today's collectible card games, live-action roleplaying games, and massively multi-player online RPGs, Cosmic Encounter was the game for everyone." Quintin Smith, in a 2014 review from Eurogamer, complimented the variety of aliens, theme, entertainment value, the negotiation mechanism, and uniqueness.

Reviews

 * Adventurer #2 (June/July, 1986)
 * Knights of the Dinner Table Magazine #109 (Nov., 2005)
 * Casus Belli #35 (Dec 1986)
 * Games #7
 * 1980 Games 100 in Games
 * 1981 Games 100 in Games
 * 1982 Games 100 in Games
 * Asimov's Science Fiction
 * Isaac Asimov's Science Fiction Magazine
 * Games & Puzzles #67
 * Jeux & Stratégie #43 (as "Rencontre cosmique")
 * The Playboy Winner's Guide to Board Games

Influence
Cosmic Encounter was one of the first commercial board games with a simple set of core rules and a specific set of modifications to those rules for each player. The game has been described as one of the innovative games from the 1970s that influenced the development of modern board games. Future Pastimes employed this technique in some of their other designs, notably the Dune board game. Steve Jackson was influenced by Cosmic Encounter when he designed Illuminati in 1982 (each player has a special power as well as a special victory condition). This design element has become more widespread in boardgames since then; it is especially applicable to games where the players represent individual characters in a role-playing game-like situation (for example, Talisman and Arkham Horror, both originally published in the 1980s).

The possibility of an organic and completely different experience every time one plays was one of the influences in the design of the card game Magic: The Gathering. Magic designer Richard Garfield has often cited Cosmic Encounter as being influential in the design of Magic, the Gathering, going so far as to say, "[Magic's] most influential ancestor is a game for which I have no end of respect: Cosmic Encounter."

title: Cosmic Encounter


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Talk:Autocorrelation

Criticism in Statistics Section - Need to Add Alternative Definition Free from Signal Processing/Determinism (I.e. in the Domain of Stochastic Processes)
In the statistics section, the definition of autocorrelation is not the same as those often given in many books on stochastic processes, and it differs from the definition given in many places on Wikipedia itself. It is a valid notation, however. For example, this notation is used in the following two books and any other books/notes on "time-series analysis".

 * Time Series Theory and Methods by Peter J. Brockwell, Richard A. Davi
 * Time series Analysis forecasting and Control by Box and Jenkins

On the other hand, I have found a definition of autocorrelation to simply be $$\mathbb{E}\left\{X_a X_b\right\}$$ for two times $$a$$ and $$b$$ in these:

 * Probability, random variables, and Stochastic Processes by Papoulis
 * Probability, Statistics, and random Processes for Electrical Engineering by Leon-Garcia
 * Discrete Optimal Filtering and Optimal Filtering by Bertein and Ceschi

In other words, the alternative definition for autocorrelation deserves to be expressed with some formality in the context of stochastic processes (i.e. $$\mathbb{E}\left\{X_a X_b\right\}$$) in the "statistics" section also. And it should be dealt with explicitly that these two functions have the same name in differing contexts (seems to be "time-series analysis" and "everywhere else"). This has several advantages of at least admitting this alternative definition exists not merely in the context of "signal processing" with its integral definition (rather than the probabilistic one with the expectation):

 * It is consistent with many other articles on Wikipedia (in the context of stochastic processes):
 * http://en.wikipedia.org/wiki/Autocorrelation_matrix . Here, the autocorrelation matrix, a generalization of the autocorrelation function, is defined without normalization.
 * http://en.wikipedia.org/wiki/Spectral_density states that "Using such formal reasoning, one may already guess that for a stationary random process, the power spectral density f(\omega) and the autocorrelation function of this signal \gamma(\tau)=\langle X(t) X(t+\tau)\rangle should be a Fourier transform pair" while clearly showing the Fourier transform of $$\mathbb{E}\left\{X_a X_b\right\}$$.
 * http://en.wikipedia.org/wiki/Wiener%E2%80%93Khinchin_theorem also calls $$\mathbb{E}\left\{X_a X_b\right\}$$ the "autocorrelation function" (while being the only of these sources to even bother to clear the confusion that autocorrelation is sometimes called autocovariance).
 * It gives a name to the quantity$$\mathbb{E}\left\{X_a X_b\right\}$$ which is often of theoretical importance (e.g. in the Wiener-Khinchin theorem). The statistical section's terminology admits no such naming of this quantity that I know of.
 * The autocorrelation defined this way has the other autocorrelation function in it with only knowledge of the mean functions u_1 and u_2. On the other hand, to go the other way, we need the mean functions u_1 and u_2 in addition to the variance functions sig_1 and sig_2 (to undo the normalization). And yes, autocorrelation defined this way ALSO has the covariance function in it if we accompany it with u_1 and u_2. Further, autocorrelation defined this way more readily brings about the second moment of the r.v. (i.e. it is more readily linked to standard random variable theory of moments and whatnot).
 * The autocorrelation function defined this way exists in situations where it will fail to exist with the other definition (when one of the variances is zero).

— Preceding unsigned comment added by 71.80.79.67 (talk) 06:59, 4 February 2014 (UTC)

 * Since that section cites no sources, you would be perfectly justified in replacing it or supplementing it with sourced content. I agree that there are at least two major sourceable definitions worth mentioning.  Dicklyon (talk) 07:33, 4 February 2014 (UTC)

 * Please excuse this comment from someone late to this party, but it makes sense to call $$\mathbb{E}\left\{X_a X_b\right\}$$ an "autocorrelation" if and only if $$\mathbb{E}\left\{X_t\right\} = 0$$ for $$t = a$$ and b. Otherwise it's not a correlation (nor an autocorrelation).

 * The section on "Auto-correlation of stochastic processes" begins by saying, "the autocorrelation of a real or complex random process is the Pearson correlation between values of the process at different times, as a function of the two times or of the time lag." This means that Eq.1 is nonsense unless $$\mathbb{E}\left\{X_t\right\} = 0$$ and the variance $$\sigma_t^2$$ = 1 for each $$t$$.

 * I suggest deleting expressions Eq.1 and Eq.3 as well as deleting the distinction between $$\operatorname{R}_{XX}(t_1,t_2)$$ and $$\operatorname{K}_{XX}(t_1,t_2)$$. ??? DavidMCEddy (talk) 02:48, 13 December 2021 (UTC)

Unclear passage
This passage:

"''For a weak-sense stationarity, wide-sense stationarity (WSS) process, the definition is

$$\rho_{XX}(\tau) = \frac{\operatorname{K}_{XX}(\tau)}{\sigma^2} = \frac{\operatorname{E} \left[(X_{t+\tau} - \mu)\overline{(X_{t} - \mu)}\right]}{\sigma^2}$$

where

$$\operatorname{K}_{XX}(0) = \sigma^2.$$''"

seems unclear to me, because to the uninitiated (like me), the phrase:

"For a weak-sense stationarity, wide-sense stationarity (WSS) process"

seems to be self-contradictory nonsense.

I hope someone knowledgeable about this subject will please rewrite this so that it does not come across as nonsense.

Please note: I am not saying that it is nonsense. But since it appears to be nonsense, this would benefit from some clarification.

Is there supposed to be an and between "weak-sense stationarity" and "wide-sense stationarity" ??? An or ??? Or what??? 2601:200:C000:1A0:300E:BD77:DEE5:AA45 (talk) 03:27, 17 August 2022 (UTC)

 * The passage you quoted contains a link to a section entitles "Weak or wide-sense stationarity" of the Wikipedia article on "Stationary process". That article begins by saying, "a stationary process (or a strict/strictly stationary process or strong/strongly stationary process) is a stochastic process whose unconditional joint probability distribution does not change when shifted in time."  That subsection says that a process is "weak-sense stationarity, wide-sense stationarity (WSS), or covariance stationarity" if the first two moments and autocovariance are finite and do not change over time.

 * From that it's clear that we could rewrite that phrase as 'For a weak-sense stationary (WSS) process (also called a "wide-sense stationary" or "covariance stationary") process'. Please feel free to make that change.  (Please excuse:  It's 1:16 AM where I am right now, and I'm going back to bed.  I believe that I tend to be more productive if I check my email in the middle of the night and spend a few minutes doing things like this.  However, I don't feel an urgency to change this myself, but if you wanted to make this change, I would encourage you to do so.  You may know that almost anyone can change almost anything on Wikipedia.  What stays tends to be written from a neutral point of view citing credible sources.  (For the policy regarding articles that can NOT be changed by anyone see see "Protection policy".  Wikipedia also has a policy encouraging people to make changes like this.  The policy is summarized as "be bold but not reckless", i.e., just do it. ;-) Users who repeatedly make changes that are obvious vandalism can be blocked.  This clearly isn't.  If a change you is not quite right for some reason, some other user will likely fix it.  As an aside, you may know that if you have an account, you can "watch" articles.  I get several emails a day telling me that articles I'm "watching" have changed and inviting me to look at the change.  That's how I saw your question.) DavidMCEddy (talk) 06:44, 17 August 2022 (UTC)

If it's obvious vadalism

DavidMCEddy (talk) 06:44, 17 August 2022 (UTC)

Contradictory definition
The section Auto-correlation of stochastic processes begins as follows:

"In statistics, the autocorrelation of a real or complex random process is the Pearson correlation between values of the process at different times, as a function of the two times or of the time lag."

The definition is then presented as

(where $$\operatorname{E}$$ is the expected value operator and the bar represents complex conjugation.)

However, this does not  use Pearson correlation, but instead uses covariance.

Later in the article it is explained that there are two conventions, one for using Pearson correlation and another for using covriance (and calllling it "correlation" anyway).

Very bad idea. The passage I quote above contradicts itself.

And regardless of whether some people misuse the word "correlation" to mean "covariance", that should not be what Wikipedia does. 2601:200:C000:1A0:1841:4827:BAAA:F4DF (talk) 15:52, 17 August 2022 (UTC)

 * Agreed. (Eq. 1) is wrong.
 * Can someone check the two references? If they contain that expression, those references are wrong -- or at least using non-standard definitions.
 * I do not have time now to fix this, but I would support others doing it. E.g., what about deleting (Eq. 1).  I suggest also deleting all equation numbers unless there are actual references.  Simple searches yielded nothing.
 * FYI: Almost anyone can change almost anything in Wikipedia.  Others change new contributions they find inappropriate.  What stays tends to be written from a neutral point of view citing credible sources.  We encourage users to Be bold but not reckless.
 * Thanks for the observation. DavidMCEddy (talk) 16:18, 17 August 2022 (UTC)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Talk:Autocorrelation


text: User talk:155.69.5.235

title: User talk:155.69.5.235


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Pressure vessel

A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.

Construction methods and materials may be chosen to suit the pressure application, and will depend on the size of the vessel, the contents, working pressure, mass constraints, and the number of items required.

Pressure vessels can be dangerous, and fatal accidents have occurred in the history of their development and operation. Consequently, pressure vessel design, manufacture, and operation are regulated by engineering authorities backed by legislation. For these reasons, the definition of a pressure vessel varies from country to country.

Design involves parameters such as maximum safe operating pressure and temperature, safety factor, corrosion allowance and minimum design temperature (for brittle fracture). Construction is tested using nondestructive testing, such as ultrasonic testing, radiography, and pressure tests. Hydrostatic pressure tests usually use water, but pneumatic tests use air or another gas. Hydrostatic testing is preferred, because it is a safer method, as much less energy is released if a fracture occurs during the test (water does not greatly increase its volume when rapid depressurization occurs, unlike gases, which expand explosively). Mass or batch production products will often have a representative sample tested to destruction in controlled conditions for quality assurance. Pressure relief devices may be fitted if the overall safety of the system is sufficiently enhanced.

In most countries, vessels over a certain size and pressure must be built to a formal code. In the United States that code is the ASME Boiler and Pressure Vessel Code (BPVC). In Europe the code is the Pressure Equipment Directive. Information on this page is mostly valid in ASME only. These vessels also require an authorized inspector to sign off on every new vessel constructed and each vessel has a nameplate with pertinent information about the vessel, such as maximum allowable working pressure, maximum temperature, minimum design metal temperature, what company manufactured it, the date, its registration number (through the National Board), and American Society of Mechanical Engineers's official stamp for pressure vessels (U-stamp). The nameplate makes the vessel traceable and officially an ASME Code vessel.

A special application is pressure vessels for human occupancy, for which more stringent safety rules apply.

History
The earliest documented design of pressure vessels was described in 1495 in the book by Leonardo da Vinci, the Codex Madrid I, in which containers of pressurized air were theorized to lift heavy weights underwater. However, vessels resembling those used today did not come about until the 1800s, when steam was generated in boilers helping to spur the industrial revolution. However, with poor material quality and manufacturing techniques along with improper knowledge of design, operation and maintenance there was a large number of damaging and often deadly explosions associated with these boilers and pressure vessels, with a death occurring on a nearly daily basis in the United States. Local provinces and states in the US began enacting rules for constructing these vessels after some particularly devastating vessel failures occurred killing dozens of people at a time, which made it difficult for manufacturers to keep up with the varied rules from one location to another. The first pressure vessel code was developed starting in 1911 and released in 1914, starting the ASME Boiler and Pressure Vessel Code (BPVC). In an early effort to design a tank capable of withstanding pressures up to 10000 psi, a 6 in diameter tank was developed in 1919 that was spirally-wound with two layers of high tensile strength steel wire to prevent sidewall rupture, and the end caps longitudinally reinforced with lengthwise high-tensile rods. The need for high pressure and temperature vessels for petroleum refineries and chemical plants gave rise to vessels joined with welding instead of rivets (which were unsuitable for the pressures and temperatures required) and in the 1920s and 1930s the BPVC included welding as an acceptable means of construction; welding is the main means of joining metal vessels today.

There have been many advancements in the field of pressure vessel engineering such as advanced non-destructive examination, phased array ultrasonic testing and radiography, new material grades with increased corrosion resistance and stronger materials, and new ways to join materials such as explosion welding, friction stir welding, advanced theories and means of more accurately assessing the stresses encountered in vessels such as with the use of Finite Element Analysis, allowing the vessels to be built safer and more efficiently. Today, vessels in the USA require BPVC stamping but the BPVC is not just a domestic code, many other countries have adopted the BPVC as their official code. There are, however, other official codes in some countries, such as Japan, Australia, Canada, Britain, and Europe. Regardless of the country, nearly all recognize the inherent potential hazards of pressure vessels and the need for standards and codes regulating their design and construction.

Shape
Pressure vessels can theoretically be almost any shape, but shapes made of sections of spheres, cylinders, and cones are usually employed. A common design is a cylinder with end caps called heads. Head shapes are frequently either hemispherical or dished (torispherical). More complicated shapes have historically been much harder to analyze for safe operation and are usually far more difficult to construct.

Theoretically, a spherical pressure vessel has approximately twice the strength of a cylindrical pressure vessel with the same wall thickness, and is the ideal shape to hold internal pressure. However, a spherical shape is difficult to manufacture, and therefore more expensive, so most pressure vessels are cylindrical with 2:1 semi-elliptical heads or end caps on each end. Smaller pressure vessels are assembled from a pipe and two covers. For cylindrical vessels with a diameter up to 600 mm (NPS of 24 in), it is possible to use seamless pipe for the shell, thus avoiding many inspection and testing issues, mainly the nondestructive examination of radiography for the long seam if required. A disadvantage of these vessels is that greater diameters are more expensive, so that for example the most economic shape of a 1000 L, 250 bar pressure vessel might be a diameter of 91.44 cm and a length of 1.7018 m including the 2:1 semi-elliptical domed end caps.

Construction materials

Many pressure vessels are made of steel. To manufacture a cylindrical or spherical pressure vessel, rolled and possibly forged parts would have to be welded together. Some mechanical properties of steel, achieved by rolling or forging, could be adversely affected by welding, unless special precautions are taken. In addition to adequate mechanical strength, current standards dictate the use of steel with a high impact resistance, especially for vessels used in low temperatures. In applications where carbon steel would suffer corrosion, special corrosion resistant material should also be used.

Some pressure vessels are made of composite materials, such as filament wound composite using carbon fibre held in place with a polymer. Due to the very high tensile strength of carbon fibre these vessels can be very light, but are much more difficult to manufacture. The composite material may be wound around a metal liner, forming a composite overwrapped pressure vessel.

Other very common materials include polymers such as PET in carbonated beverage containers and copper in plumbing.

Pressure vessels may be lined with various metals, ceramics, or polymers to prevent leaking and protect the structure of the vessel from the contained medium. This liner may also carry a significant portion of the pressure load.

Pressure Vessels may also be constructed from concrete (PCV) or other materials which are weak in tension. Cabling, wrapped around the vessel or within the wall or the vessel itself, provides the necessary tension to resist the internal pressure. A "leakproof steel thin membrane" lines the internal wall of the vessel. Such vessels can be assembled from modular pieces and so have "no inherent size limitations". There is also a high order of redundancy thanks to the large number of individual cables resisting the internal pressure.

The very small vessels used to make liquid butane fueled cigarette lighters are subjected to about 2 bar pressure, depending on ambient temperature. These vessels are often oval (1 x 2 cm ... 1.3 x 2.5 cm) in cross section but sometimes circular. The oval versions generally include one or two internal tension struts which appear to be baffles but which also provide additional cylinder strength.

Working pressure
The typical circular-cylindrical high pressure gas cylinders for permanent gases (that do not liquify at storing pressure, like air, oxygen, nitrogen, hydrogen, argon, helium) have been manufactured by hot forging by pressing and rolling to get a seamless steel vessel.

Working pressure of cylinders for use in industry, skilled craft, diving and medicine had a standardized working pressure (WP) of only 150 bar in Europe until about 1950. From about 1975 until now, the standard pressure is 200 bar. Firemen need slim, lightweight cylinders to move in confined spaces; since about 1995 cylinders for 300 bar WP were used (first in pure steel).

A demand for reduced weight led to different generations of composite (fiber and matrix, over a liner) cylinders that are more easily damageable by a hit from outside. Therefore, composite cylinders are usually built for 300 bar.

Hydraulic (filled with water) testing pressure is usually 50% higher than the working pressure.

Vessel thread
Until 1990, high pressure cylinders were produced with conical (tapered) threads. Two types of threads have dominated the full metal cylinders in industrial use from 0.2 to 50 L in volume. Taper thread (17E), with a 12% taper right hand thread, standard Whitworth 55° form with a pitch of 14 threads per inch (5.5 threads per cm) and pitch diameter at the top thread of the cylinder of 18.036 mm. These connections are sealed using thread tape and torqued to between 120 and 150 Nm on steel cylinders, and between 75 and 140 Nm on aluminium cylinders. To screw in the valve, a high torque of typically 200 Nm is necessary for the larger 25E taper thread, and 100 Nm for the smaller 17E thread. Until around 1950, hemp was used as a sealant. Later, a thin sheet of lead pressed to a hat with a hole on top was used. Since 2005, PTFE-tape has been used to avoid using lead.

A tapered thread provides simple assembly, but requires high torque for connecting and leads to high radial forces in the vessel neck. All cylinders built for 300 bar working pressure, all diving cylinders, and all composite cylinders use parallel threads. Parallel threads are made to several standards: The 3/4"NGS and 3/4"BSP are very similar, having the same pitch and a pitch diameter that only differs by about 0.2 mm, but they are not compatible, as the thread forms are different.
 * M25x2 ISO parallel thread, which is sealed by an O-ring and torqued to 100 to 130 Nm on steel, and 95 to 130 Nm on aluminium cylinders;
 * M18x1.5 parallel thread, which is sealed by an O-ring, and torqued to 100 to 130 Nm on steel cylinders, and 85 to 100 Nm on aluminium cylinders;
 * 3/4"x14 BSP parallel thread, which has a 55° Whitworth thread form, a pitch diameter of 25.279 mm and a pitch of 14 threads per inch (1.814 mm);
 * 3/4"x14 NGS (NPSM) parallel thread, sealed by an O-ring, torqued to 40 to 50 Nm on aluminium cylinders, which has a 60° thread form, a pitch diameter of 0.9820 to 0.9873 in, and a pitch of 14 threads per inch (5.5 threads per cm);
 * 3/4"x16 UNF, sealed by an O-ring, torqued to 40 to 50 Nm on aluminium cylinders.
 * 7/8"x14 UNF, sealed by an O-ring.

All parallel thread valves are sealed using an elastomer O-ring at top of the neck thread which seals in a chamfer or step in the cylinder neck and against the flange of the valve.

Development of composite vessels
To classify the different structural principles cylinders, 4 types are defined.

 * Type 1 – Full metal: Cylinder is made entirely from metal.
 * Type 2 – Hoop wrap: Metal cylinder, reinforced by a belt-like hoop wrap with fibre-reinforced resin.
 * Type 3 – Fully wrapped, over metal liner: Diagonally wrapped fibres form the load bearing shell on the cylindrical section and at the bottom and shoulder around the metal neck. The metal liner is thin and provides the gas tight barrier.
 * Type 4 – Fully wrapped, over non-metal liner: A lightweight thermoplastic liner provides the gas tight barrier, and the mandrel to wrap fibres and resin matrix around. Only the neck which carries the neck thread and its anchor to the liner is made of metal, which may be lightweight aluminium or sturdy stainless steel.

Type 2 and 3 cylinders have been in production since around 1995. Type 4 cylinders are commercially available at least since 2016.

Leak before burst
Leak before burst describes a pressure vessel designed such that a crack in the vessel will grow through the wall, allowing the contained fluid to escape and reducing the pressure, prior to growing so large as to cause fracture at the operating pressure.

Many pressure vessel standards, including the ASME Boiler and Pressure Vessel Code and the AIAA metallic pressure vessel standard, either require pressure vessel designs to be leak before burst, or require pressure vessels to meet more stringent requirements for fatigue and fracture if they are not shown to be leak before burst.

Safety valves

As the pressure vessel is designed to a pressure, there is typically a safety valve or relief valve to ensure that this pressure is not exceeded in operation.

Pressure vessel closures
Pressure vessel closures are pressure retaining structures designed to provide quick access to pipelines, pressure vessels, pig traps, filters and filtration systems. Typically pressure vessel closures allow access by maintenance personnel. A commonly used access hole shape is elliptical, which allows the closure to be passed through the opening, and rotated into the working position, and is held in place by a bar on the outside, secured by a central bolt. The internal pressure prevents it from being inadvertently opened under load.

Uses
Pressure vessels are used in a variety of applications in both industry and the private sector. They appear in these sectors as industrial compressed air receivers, boilers and domestic hot water storage tanks. Other examples of pressure vessels are diving cylinders, recompression chambers, distillation towers, pressure reactors, autoclaves, and many other vessels in mining operations, oil refineries and petrochemical plants, nuclear reactor vessels, submarine and space ship habitats, atmospheric diving suits, pneumatic reservoirs, hydraulic reservoirs under pressure, rail vehicle airbrake reservoirs, road vehicle airbrake reservoirs, and storage vessels for high pressure permanent gases and liquified gases such as ammonia, chlorine, and LPG (propane, butane).

A unique application of a pressure vessel is the passenger cabin of an airliner: the outer skin carries both the aircraft maneuvering loads and the cabin pressurization loads.

Alternatives
Depending on the application and local circumstances, alternatives to pressure vessels exist. Examples can be seen in domestic water collection systems, where the following may be used:
 * Natural gas storage
 * Gas holder
 * Gravity-controlled systems which typically consist of an unpressurized water tank at an elevation higher than the point of use. Pressure at the point of use is the result of the hydrostatic pressure caused by the elevation difference. Gravity systems produce 0.43 psi per foot of water head (elevation difference). A municipal water supply or pumped water is typically around 90 psi.
 * Inline pump controllers or pressure-sensitive pumps.
 * In nuclear reactors, pressure vessels are primarily used to keep the coolant (water) liquid at high temperatures to increase Carnot efficiency. Other coolants can be kept at high temperatures with much less pressure, explaining the interest in molten salt reactors, lead cooled fast reactors and gas cooled reactors. However, the benefits of not needing a pressure vessel or one of less pressure are in part compensated by drawbacks unique to each alternative approach.

Scaling
No matter what shape it takes, the minimum mass of a pressure vessel scales with the pressure and volume it contains and is inversely proportional to the strength to weight ratio of the construction material (minimum mass decreases as strength increases ).

Scaling of stress in walls of vessel
Pressure vessels are held together against the gas pressure due to tensile forces within the walls of the container. The normal (tensile) stress in the walls of the container is proportional to the pressure and radius of the vessel and inversely proportional to the thickness of the walls. Therefore, pressure vessels are designed to have a thickness proportional to the radius of tank and the pressure of the tank and inversely proportional to the maximum allowed normal stress of the particular material used in the walls of the container.

Because (for a given pressure) the thickness of the walls scales with the radius of the tank, the mass of a tank (which scales as the length times radius times thickness of the wall for a cylindrical tank) scales with the volume of the gas held (which scales as length times radius squared). The exact formula varies with the tank shape but depends on the density, ρ, and maximum allowable stress σ of the material in addition to the pressure P and volume V of the vessel. (See below for the exact equations for the stress in the walls.)

Spherical vessel
For a sphere, the minimum mass of a pressure vessel is

 * $$M = {3 \over 2} P V {\rho \over \sigma}$$,

where:
 * $$M$$ is mass, (kg)
 * $$P$$ is the pressure difference from ambient (the gauge pressure), (Pa)
 * $$V$$ is volume,
 * $$\rho$$ is the density of the pressure vessel material, (kg/m3)
 * $$\sigma$$ is the maximum working stress that material can tolerate. (Pa)

Other shapes besides a sphere have constants larger than 3/2 (infinite cylinders take 2), although some tanks, such as non-spherical wound composite tanks can approach this.

Cylindrical vessel with hemispherical ends
This is sometimes called a "bullet" for its shape, although in geometric terms it is a capsule.

For a cylinder with hemispherical ends,
 * $$M = 2 \pi R^2 (R + W) P {\rho \over \sigma}$$,

where
 * R is the Radius (m)
 * W is the middle cylinder width only, and the overall width is W + 2R (m)

Cylindrical vessel with semi-elliptical ends
In a vessel with an aspect ratio of middle cylinder width to radius of 2:1,
 * $$M = 6 \pi R^3 P {\rho \over \sigma}$$.

Gas storage
In looking at the first equation, the factor PV, in SI units, is in units of (pressurization) energy. For a stored gas, PV is proportional to the mass of gas at a given temperature, thus
 * $$M = {3 \over 2} nRT {\rho \over \sigma}$$. (see gas law)

The other factors are constant for a given vessel shape and material. So we can see that there is no theoretical "efficiency of scale", in terms of the ratio of pressure vessel mass to pressurization energy, or of pressure vessel mass to stored gas mass. For storing gases, "tankage efficiency" is independent of pressure, at least for the same temperature.

So, for example, a typical design for a minimum mass tank to hold helium (as a pressurant gas) on a rocket would use a spherical chamber for a minimum shape constant, carbon fiber for best possible $$\rho / \sigma$$, and very cold helium for best possible $$M / {pV}$$.

Stress in thin-walled pressure vessels
Stress in a thin-walled pressure vessel in the shape of a sphere is
 * $$\sigma_\theta = \sigma_{\rm long} = \frac{pr}{2t}$$,

where $$\sigma_\theta$$ is hoop stress, or stress in the circumferential direction, $$\sigma_{long}$$ is stress in the longitudinal direction, p is internal gauge pressure, r is the inner radius of the sphere, and t is thickness of the sphere wall. A vessel can be considered "thin-walled" if the diameter is at least 10 times (sometimes cited as 20 times) greater than the wall thickness.

Stress in a thin-walled pressure vessel in the shape of a cylinder is
 * $$\sigma_\theta = \frac{pr}{t}$$,
 * $$\sigma_{\rm long} = \frac{pr}{2t}$$,

where:
 * $$\sigma_\theta$$ is hoop stress, or stress in the circumferential direction
 * $$\sigma_{long}$$ is stress in the longitudinal direction
 * p is internal gauge pressure
 * r is the inner radius of the cylinder
 * t is thickness of the cylinder wall.

Almost all pressure vessel design standards contain variations of these two formulas with additional empirical terms to account for variation of stresses across thickness, quality control of welds and in-service corrosion allowances. All formulae mentioned above assume uniform distribution of membrane stresses across thickness of shell but in reality, that is not the case. Deeper analysis is given by Lamé's theorem, which gives the distribution of stress in the walls of a thick-walled cylinder of a homogeneous and isotropic material. The formulae of pressure vessel design standards are extension of Lamé's theorem by putting some limit on ratio of inner radius and thickness.

For example, the ASME Boiler and Pressure Vessel Code (BPVC) (UG-27) formulas are: Spherical shells: Thickness has to be less than 0.356 times inner radius
 * $$\sigma_\theta = \sigma_{\rm long} = \frac{p(r + 0.2t)}{2tE}$$

Cylindrical shells: Thickness has to be less than 0.5 times inner radius
 * $$\sigma_\theta = \frac{p(r + 0.6t)}{tE}$$
 * $$\sigma_{\rm long} = \frac{p(r - 0.4t)}{2tE}$$

where E is the joint efficiency, and all others variables as stated above.

The factor of safety is often included in these formulas as well, in the case of the ASME BPVC this term is included in the material stress value when solving for pressure or thickness.

Winding angle of carbon fibre vessels
Wound infinite cylindrical shapes optimally take a winding angle of 54.7 degrees to the cylindrical axis, as this gives the necessary twice the strength in the circumferential direction to the longitudinal.

Riveted
The standard method of construction for boilers, compressed air receivers and other pressure vessels of iron or steel before gas and electrical welding of reliable quality became widespread was riveted sheets which had been rolled and forged into shape, then riveted together, often using butt straps along the joints, and caulked along the riveted seams by deforming the edges of the overlap with a blunt chisel. Hot riveting caused the rivets to contract on cooling, forming a tighter joint.

Seamless
Manufacturing methods for seamless metal pressure vessels are commonly used for relatively small diameter cylinders where large numbers will be produced, as the machinery and tooling require large capital outlay. The methods are well suited to high pressure gas transport and storage applications, and provide consistently high quality products.

Backward extrusion: A process by which the material is forced to flow back along the mandrel between the mandrel and die.

Cold extrusion (aluminium):

Seamless aluminium cylinders may be manufactured by cold backward extrusion of aluminium billets in a process which first presses the walls and base, then trims the top edge of the cylinder walls, followed by press forming the shoulder and neck.

Hot extrusion (steel):

In the hot extrusion process a billet of steel is cut to size, induction heated to the correct temperature for the alloy, descaled and placed in the die. The metal is backward extruded by forcing the mandrel into it, causing it to flow through the annular gap until a deep cup is formed. This cup is further drawn to diameter and wall thickness reduced and the bottom formed. After inspection and trimming of the open end The cylinder is hot spun to close the end and form the neck.

Drawn: Seamless cylinders may also be cold drawn from steel plate discs to a cylindrical cup form, in two or three stages. After forming the base and side walls, the top of the cylinder is trimmed to length, heated and hot spun to form the shoulder and close the neck. This process thickens the material of the shoulder. The cylinder is heat-treated by quenching and tempering to provide the best strength and toughness.

Regardless of the method used to form the cylinder, it will be machined to finish the neck and cut the neck threads, heat treated, cleaned, and surface finished, stamp marked, tested, and inspected for quality assurance.

Welded
Large and low pressure vessels are commonly manufactured from formed plates welded together. Weld quality is critical to safety in pressure vessels for human occupancy.

Composite
Composite pressure vessels are generally filament wound rovings in a thermosetting polymer matrix. The mandrel may be removable after cure, or may remain a part of the finished product, often providing a more reliable gas or liquid-tight liner, or better chemical resistance to the intended contents than the resin matrix. Metallic inserts may be provided for attaching threaded accessories, such as valves and pipes.

Operation standards
Pressure vessels are designed to operate safely at a specific pressure and temperature, technically referred to as the "Design Pressure" and "Design Temperature". A vessel that is inadequately designed to handle a high pressure constitutes a very significant safety hazard. Because of that, the design and certification of pressure vessels is governed by design codes such as the ASME Boiler and Pressure Vessel Code in North America, the Pressure Equipment Directive of the EU (PED), Japanese Industrial Standard (JIS), CSA B51 in Canada, Australian Standards in Australia and other international standards like Lloyd's, Germanischer Lloyd, Det Norske Veritas, Société Générale de Surveillance (SGS S.A.), Lloyd's Register Energy Nederland (formerly known as Stoomwezen) etc.

Note that where the pressure-volume product is part of a safety standard, any incompressible liquid in the vessel can be excluded as it does not contribute to the potential energy stored in the vessel, so only the volume of the compressible part such as gas is used.

List of standards

 * EN 13445: The current European Standard, harmonized with the Pressure Equipment Directive (Originally "97/23/EC", since 2014 "2014/68/EU"). Extensively used in Europe.
 * ASME Boiler and Pressure Vessel Code Section VIII: Rules for Construction of Pressure Vessels.
 * BS 5500: Former British Standard, replaced in the UK by BS EN 13445 but retained under the name PD 5500 for the design and construction of export equipment.
 * AD Merkblätter: German standard, harmonized with the Pressure Equipment Directive.
 * EN 286 (Parts 1 to 4): European standard for simple pressure vessels (air tanks), harmonized with Council Directive 87/404/EEC.
 * BS 4994: Specification for design and construction of vessels and tanks in reinforced plastics.
 * ASME PVHO: US standard for Pressure Vessels for Human Occupancy.
 * CODAP: French Code for Construction of Unfired Pressure Vessel.
 * AS/NZS 1200: Australian and New Zealand Standard for the requirements of Pressure equipment including Pressure Vessels, boilers and pressure piping.
 * AS 1210: Australian Standard for the design and construction of Pressure Vessels
 * AS/NZS 3788: Australian and New Zealand Standard for the inspection of pressure vessels
 * API 510.
 * ISO 11439: Compressed natural gas (CNG) cylinders
 * IS 2825–1969 (RE1977)_code_unfired_Pressure_vessels.
 * FRP tanks and vessels.
 * AIAA S-080-1998: AIAA Standard for Space Systems – Metallic Pressure Vessels, Pressurized Structures, and Pressure Components.
 * AIAA S-081A-2006: AIAA Standard for Space Systems – Composite Overwrapped Pressure Vessels (COPVs).
 * ECSS-E-ST-32-02C Rev.1: Space engineering – Structural design and verification of pressurized hardware
 * B51-09 Canadian Boiler, pressure vessel, and pressure piping code.
 * HSE guidelines for pressure systems.
 * Stoomwezen: Former pressure vessels code in the Netherlands, also known as RToD: Regels voor Toestellen onder Druk (Dutch Rules for Pressure Vessels).
 * SANS 10019:2021 South African National Standard: Transportable pressure receptacles for compressed, dissolved and liquefied gases - Basic design, manufacture, use and maintenance.
 * SANS 1825:2010 Edition 3: South African National Standard: Gas cylinder test stations ― General requirements for periodic inspection and testing of transportable refillable gas pressure receptacles. ISBN 978-0-626-23561-1

title: Pressure vessel


text:
Advanced Squad Leader

Advanced Squad Leader (ASL) is a tactical-level board wargame, originally marketed by Avalon Hill Games, that simulates actions of squad sized units in World War II. It is a detailed game system for two or more players (with solitary play also possible). Components include the ASL Rulebook and various games called modules. ASL modules provide the standard equipment for playing ASL, including geomorphic mapboards and counters. The mapboards are divided into hexagons to regulate fire and movement, and depict generic terrain that can represent different historical locations. The counters are cardboard pieces that depict squads of soldiers, crews, individual leaders, support weapons, heavy weapons, and vehicles.

Combined with the sales of the original Squad Leader, Advanced Squad Leader sold over 1 million copies by 1997.

Introduction
Fifteen core modules provide representations of nearly every troop type, vehicle, and weapon to see combat action from any nationality involved in World War II. Each module comes with 6 to 20 researched scenarios depicting historical battles. These scenarios are printed on card stock with specifications of game length, map board configuration, counters involved, special rules for the conditions of the particular battle such as weather, and victory conditions. In addition to the scenarios published in the modules, there are numerous other sources for scenarios, both official and unofficial. There is also a detailed set of instructions in the ASL Rulebook for Design Your Own (DYO) scenarios based on a point-purchase system.

Additional variations on ASL include Deluxe ASL (DASL), which was a short-lived experiment in fusing miniature wargaming with ASL; Historical ASL (HASL), which used historically accurate maps, usually in a campaign setting where the outcome of one scenario affected the setup of following scenarios; Solitaire ASL (SASL) with many rules changes for fog of war and command to enhance solitaire play; and the ASL Starter Kits (ASLSK), a series of stand-alone introductory kits.

The game was first published by Avalon Hill in 1985 as a successor to the award-winning Squad Leader series, on which the game is based and from which the rules and components were directly developed. By the time the fourth and final installment of Squad Leader debuted, there were four separate rulebooks in existence with poorly integrated and sometimes contradictory rules. For example, U.S. forces had lower morale and were therefore disadvantaged by the use of morale ratings to determine the ability to push ordnance through snow or mud, even though there is no real reason for morale to affect such an attempt. It was clear that the system had grown in ways never dreamed of in 1977; large amounts of "nutmail" to Avalon Hill convinced the developers of the need to streamline the rules.

ASL
Avalon Hill had originally promised a new rulebook streamlining procedures, eliminating redundancies, and possibly revising the "To Hit/To Kill" system used to simulate armor protection and penetration in tank combat. Instead, by the time it debuted, Advanced Squad Leader had become a complete replacement of the games of the original SL series. As an example, the original SL has only twelve different tank and assault gun types, and only five different armor ratings, from -2 to +2. By contrast, ASL has separate counters for 56 different types of tanks and assault guns for the Germans alone, with armor values from 0 to 26, based on actual thickness and degree of slope. Beyond Valor includes 99 separate German vehicles simulated in the game, including halftracks, armored cars, anti-aircraft vehicles, and soft skins.

Many fans of the original Squad Leader game who had looked forward to improvements to the system with the release of Advanced Squad Leader were taken aback by the need to replace the four modules they had bought; only the map boards of the earlier series were compatible with the new game.

The new game requires at least two products, the Advanced Squad Leader Rulebook and an initial module, either Beyond Valor, which contains a brand new counter mix for the German, Russian and Finnish armies, as well as all necessary system counters, or else Paratrooper, which contains a limited counter mix for system markers, US paratrooper units and their German opponents in Normandy. Either initial module also requires ownership of boards from SL in order to play the included scenarios.

The new game does not feature programmed instruction, instead of requiring a thorough reading of at least four chapters of the ASL Rulebook to play a game with ordnance and/or vehicles in it. Even the most basic ASL components were no longer introductory in nature, although Paratrooper masqueraded as such. (This would be redressed in 2004 by the introduction of ASL Starter Kits). Avalon Hill actually suggested that anyone wishing to play ASL also purchase the original Squad Leader and gain experience with that system first, and kept the original SL and three gamettes in print. The necessity of owning boards from these modules in order to play printed scenarios in the core modules of ASL may also have been a factor in this decision. So while ASL was intended to replace SL, there was a certain ambiguity for many years about the status of SL's replacement; the original game was still necessary as a stepping stone to learning ASL, and a source for needed map boards.

ASL was the first of Avalon Hill's 'advanced' games (the others were Advanced Civilization and Advanced Third Reich).

In 1998 Monarch Avalon, Inc. sold its entire line of games to Hasbro. On January 15, 1999, Multi-Man Publishing, LLC (MMP) announced an exclusive association with Hasbro, Inc. "to develop, produce, and distribute games and other products for Avalon Hill's Advanced Squad Leader (ASL) game system." MMP is a gaming company founded in 1994 by Perry Cocke and Brian Youse, and later co-partner Curt Schilling, to preserve ASL and other Avalon Hill games. Multi-Man Publishing made many changes to the new system; a decision not to reprint the earlier Squad Leader games resulted in reorganization and 2nd editions of many ASL core modules in order to include boards from the earlier games, necessary for play of the printed scenarios in those core modules.

Playtester Jon Mishcon described the new game rather more succinctly in Volume 21, Number 5 of The General Magazine, in relation to Squad Leader; he wrote that the game was "Closely akin to SL but NOT the same." ASL took longer to play, punished use of "cheats" that worked in the old game system (one example was flooding an isolated defending unit by moving multiple units towards him; in ASL, units could fire more than once at moving targets in certain situations, which was impossible in the original SL), and emphasized realism over playability. He clarified that while playability had in many cases increased with the organization of the new rules, there were still many "special" circumstances that called for special rules. The new rules did, however, have a very strong systemic approach whereby, in his words, you could

"learn a concept and it applies, with varying D (ice) R (oll) M (odifiers), in all similar situations. This makes the game easier to learn and play. The rules make more sense.  Most of the old 'funny' rules that allowed 'cute' tricks have been deleted.  Mostly, I guess, it's a distillation of the best of SL....In short, there's a lot less crapping around in the rules.  Most importantly, the vast majority of the rules really will tend to benefit the player who thinks as did his historical counterpart.  (Sigh, an end to our torching most of the map board.)"

In that same issue of The General, Don Greenwood - developer of ASL and also editor of the magazine - responded to harsh criticism by consumers who felt that the redesign of the system was a cash-grab, or worse, a betrayal.

"The SL game system, for all its acclaim...was based on a flawed foundation. The subsequent gamettes, in building on that start, only complicated matters by attempting to patch that foundation rather than replace it altogether....here's how I rationalize it. A few years ago, ...I was so enamored by (video cassette recorders) that I just had to have one.  Two years later they were selling models for half the price with twice the features which mine had.  Sometimes I regret buying that VCR so soon, but then I recall all the fun I had with it when it was new and eventually concluded that my money was well spent after all."

Despite the price tag and the expensive lists of prerequisites for each new module, the game system caught on and new modules continued to be produced twenty-five years after the original release - joining Dungeons & Dragons and Star Fleet Battles as one of what were known as "The Big Three" games of the hobbyist game industry. A large and active worldwide hobby community thrives around ASL, including tournaments, community websites, clubs, and fanzines. An active trading and auction community enables participants to buy and sell used ASL modules. ASL can be played over the Internet using a system called Virtual Advanced Squad Leader (VASL), using the "Vassal" game engine designed by Rodney Kinney. This is a Java-based application that allows for real-time input by one or more participants/observers who can manipulate graphical representations of map boards and counters, including random dice rolls, LOS checking, chart consultation and all the necessary administrative tasks to play a full game of ASL.

A number of third-party developers also continue to publish modules and scenarios for ASL.

ASL rulebook
The ASL Rulebook was reformatted away from the traditional Avalon Hill format used in their smaller games. The ASL Rulebook was modeled after Amarillo Design Bureau's Star Fleet Battles rulebook, a format that better supported the "massive" game that ASL had become. Based on military field manuals, the rule book was contained in a three-ring binder. Each chapter was color-coded along the top of the page, with brightly colored section dividers of heavy cardboard stock reproducing charts and diagrams associated with that chapter. Errata would be provided on a regular basis, and coupons in the back of the rulebook could be exchanged by mail for the initial updates to the rulebook. The errata would come in the form of altered pages, with page numbers annotated with the date of any changes; old pages were simply removed from the binder and discarded and the new page inserted. The two largest updates were the '87 and '89 sections that came with many pages. The first edition rules shipped with Chapter A, B, C, D, H, J, and N. Chapter N was a visual inventory of all game pieces included in Beyond Valor and several follow up modules but was not fully supported. While early modules did contain the appropriate Chapter N pages, some modules did not have the pages included immediately (Paratrooper's Chapter N pages, for example, were not provided until the release of Yanks). HASL modules did not have associated Chapter N pages, and neither did Doomed Battalions.

The rules themselves were heavily streamlined, as promised, though many more procedures were introduced to the game, increasing complexity and playing time (as well as the likelihood of rules arguments). The modelling of infantry weapons was overhauled to prevent unrealistic tactics, and machineguns and ordnance were given variable rates of fire (in other words, the ability to fire more than once per phase, with a certain unpredictability as to how many times worked in). Squads equipped only with small arms now had many options to reflect weapons types; semi-automatic and automatic weapons could be simulated with rules for Spraying Fire or Assault Fire, for example.

Above all, the use of standardized abbreviations and jargon made the rules very technical in outlook; this language is known as "legalese" and is in contrast to more "conversational" types of rules. The debate of the merits of both approaches went as far back as the original Squad Leader rulebook written by John Hill and Don Greenwood. ASL came down firmly on the side of "legalese", though not coincidentally Don Greenwood was the driving force behind ASL with John Hill having moved on to other projects after the original SL.

A 2nd Edition Rulebook was introduced by Multi-Man Publishing in early 2001, combining all previous errata and including updates to Chapters A, B, C, D, H (German/Russian), and J as well as Chapter E (previously available only with the Yanks module) and Chapter K Days 1-8 (previously available only with the Paratrooper Module (Days 1-6), Pegasus Bridge HASL Module (Day 7) and ASL Journal #2 (Day 8)).

All Historical ASL Module rules associated with Historical Study Modules and the ASL Journal were incorporated into a new Chapter Z.

Chapter N is no longer supported in the 2nd Edition ASL Rulebook, and all Chapter N pages have been deleted from reprinted modules. The new rulebook also includes (minor) material not covered in any previous issue of errata, making ownership of the 2nd Edition essential for compatibility with new products or other players who use the 2nd Edition. The 2nd Edition does reflect most, but not all, previous changes to the rules via an issue of replacement pages. There are also cosmetic differences such as larger typeface and improved layout.

Unique elements
Perhaps one of the most unusual elements of the ASL system is the use of dice. While using two dice to obtain a bell curve result between 2 and 12 (36 possible outcomes) is not unique to ASL, there are many other ways in which the dice are used. One die is a "colored" die, so that when two dice are rolled, not only will the sum of both dice be used (for example, an attack by a machinegun on an enemy unit will have the result of two dice cross-referenced on the Infantry Fire Table (IFT)), but other results may also be achieved simultaneously. (To continue the example, if the colored die is equal or less to a printed Rate of Fire (ROF) number given for the machinegun, it may fire again in that phase). Comparing the results of the two dice to each other will also create simultaneous results; so while the sum of the dice will be used on the IFT, two sixes (a natural 12) will result in the machinegun suffering a stoppage. If the roll was for an attack by an infantry squad, identical results on both dice would result in "cowering" and a different column on the IFT would be consulted with the dice roll. Double ones will result in a Critical Hit if rolling for an ordnance weapon "To Hit" an enemy target. As well, ASL gives each side in most scenarios a Sniper Activation Number (SAN) that will activate a random sniper attack whenever one side rolls the other's SAN for any purpose during gameplay. The dice thus feature heavily in gameplay providing multiple random events every time they are rolled.

ASL modules
The following is a list of Advanced Squad Leader Modules, and the dates of their release. There were complex prerequisites for just about all modules after the release of Beyond Valor and Paratrooper, and 2nd Editions of most of the following have reorganized the map boards and rules chapters released with each. Specifically, a re-release of boards 1 to 4 has been necessary given MMPs decision not to reprint the original Squad Leader game and its three gamettes.

The original Avalon Hill West of Alamein module originally contained the entire British/Commonwealth order of battle; reprintings by MMP have reorganized the content, splitting the original WOA content into two modules, a 2nd Edition West of Alamein, and a new For King and Country module.
 * 1—Beyond Valor (1985)
 * 2—Paratrooper (1986)
 * 3—Yanks (1987)
 * 3a-Yanks (2016 reprint)
 * 4—Partisan! (1987)
 * 5—West of Alamein (1988)
 * 5a—For King and Country (2004)
 * 6—The Last Hurrah (1988)
 * 7—Hollow Legions (1989)
 * 8—Code of Bushido (1990)
 * 9—Gung Ho! (1991)
 * 10—Croix de Guerre (1992)
 * 10a—Croix de Guerre (2020)
 * 11—Doomed Battalions (1998)
 * 12—Armies of Oblivion (2006)
 * 13—Rising Sun (2013)
 * 14—Hakkaa Päälle (2015)
 * 15—Forgotten War (2017)

ASL module prerequisites
A tremendous strength in the ASL system is its flexibility. Most tactical situations from Second World War history can be recreated using the components of the game system. However, special rules, maps, or map overlays may be required in order to properly portray these situations. ASL modules usually have dependencies on one or more previous module(s) (in other words, use of the material in one module is dependent on ownership of another). Very few modules can be played in isolation.

This is not a complete list.

As well, the problem of prerequisites extends to the playing of printed scenarios, many of which require components from multiple modules, particularly those scenarios released by third-party publishers. For instance, the Order of Battle (OOB) from a module may be needed to play one module while a single map board from the same module may be required to play a particular scenario. The Hollow Legions (HL) Module was originally intended to add on to West of Alamein (WOA) and as such the OOB from For King and Country will not be enough to play all scenarios in HL as the WOA map boards are required as well. Furthermore, an MMP Action Pack is required for one module, a Historical Study.

Finally, the release of the 2nd Edition rules further complicates the process by making some sections of the 1st Edition obsolete. Full compatibility with 2nd Edition rules is only possible by owning the 2nd Edition. This forces some players to purchase the ASLRB all over again. An area the new rules simplifies is the Chapters included in various Modules. Originally a new module would add a new chapter to the ASLRB to cover the new material. For instance, the release of Yanks included special rules in Chapter E and a chapter detailing the American OOB. Any players wishing to use these rules in a following Module would also have to own Yanks. The 2nd Edition helps to alleviate this problem by supplying more rules in one binder. It still does not supply all rules for all situations. For instance, if you wish to play a scenario using Jungle terrain you will need the Code of Bushido module with its rules section. Also, the OOB of particular nationalities and the map boards from particular Modules may still be required for subsequent Modules.

ASL Action Packs
ASL Action Packs (AP) are published by MMP. They include new scenarios and boards. They do not contain new rules or counters, with the exception of AP 2 and AP 4 which have new rule pages inserts.

 * 1-Action Pack 1 (AH, 1997)
 * 2-Action Pack 2 (MMP, 1999)
 * 3-Action Pack 3: Few Returned (MMP, 2007)
 * 4-Action Pack 4: Normandy (MMP, 2008)
 * 5-Action Pack 5: Eastern Front (MMP, 2009)
 * 6-Action Pack 6: A Decade of War (MMP, 2010)
 * 7-Action Pack 7 (MMP, 2011)
 * 8-Action Pack 8: Roads Through Rome (MMP, 2011)
 * 9-Action Pack 9: To the Bridge! (MMP, 2014)
 * 10-Action Pack 10 (MMP, 2014)
 * 11-Action Pack 11: 29 Let's Go! (MMP, 2015)
 * 12-Action Pack 12: ASLOK XXX(MMP,2015)

Deluxe ASL
Deluxe Advanced Squad Leader (DASL) was a version of the Advanced Squad Leader game introduced in 1985. Intended to be a fusion of 1:285 scale miniatures (so-called "micro-armor") and Squad Leader, the concept never really took off, at least in the printed form sold by Avalon Hill, and only two modules were released, both in 1985.

The 1st edition ASL Rulebook contained a chapter on painting 1:285 scale miniatures, and the Deluxe Advanced Squad Leader Modules were released soon after Beyond Valor. These map boards were 11" by 26" and had greatly enlarged hex grids, each hex being 2.2" inches across. The maps were designed to be used in conjunction with 1:285 scale miniatures, but could naturally be used with the standard cardboard counters and a very brief rulebook chapter gave some additional special rules for using the cardboard counters in the larger hexes. Only two modules were released; the drawback of the larger scale map boards was that the terrain being simulated had to be fairly close-in, and scenarios based on fighting in these kinds of environments. The two official releases focused on city fighting and the hedgerow country in Normandy.

In 2020, the DASL system was re-released. Included were the original 18 scenarios from the first two releases, as well as a further 20 scenarios, all updated scenarios previously released.

Streets of Fire
Streets of Fire was the first Deluxe ASL module to be released; the maps were very similar and depicted city terrain similar to that found on the mapboard 1 from Squad Leader or the "city boards" found in Beyond Valor.

Hedgerow Hell
Hedgerow Hell was the second Deluxe ASL module to be released. The maps represented typical bocage country, with many hedge depictions and more rural type terrain types.

Deluxe ASL
Deluxe ASL was released in 2020 at Winter Offensive in Bowie, Maryland. Its maps were the tri-fold style, repainted by Charlie Kibler and printed on card stock, the so-called "SK" style boards. Also included were all of the original Deluxe ASL overlays (from the 1995 Annual), also repainted by Charlie, and two sheets of *new* overlays and four additional sheets of wooden and stone rubble Kibler overlays

Historical ASL
Several modules known as Historical Advanced Squad Leader modules, or HASL, feature maps based on actual terrain as well as historical "campaigns" (known as Campaign Games (CG)) where interlinked scenarios depict several days of fighting over historical objectives. MMP took over production of HASL with A Bridge Too Far, and also released "Historical Studies", or modules in which the geomorphic mapboards were sometimes substituted for actual terrain maps.

HASL modules

 * 1989: Red Barricades
 * 1993: Kampfgruppe Peiper I
 * 1995: Kampfgruppe Peiper II
 * 1996: Pegasus Bridge
 * 1999: A Bridge Too Far
 * 1999: Blood Reef: Tarawa
 * 2001: Operation Watchtower (historical study)
 * 2002: Operation Veritable (historical study)
 * 2008: Valor of the Guards
 * 2012: Festung Budapest
 * 2018: Hatten in Flames
 * 2019: Red Factories (incorporates reissued Red Barricades)

Solitaire ASL
A module designed for solitaire play was designed by MMP, using dice and charts to generate opposing actions, in a system similar to earlier solitaire games like Ambush! or Tokyo Express. Only one module has been released, and MMP has announced that no reprint will be made. No new boards were released with the module, though Chapter S was included covering the special rules for SASL (a 2nd edition was released with expanded solitaire rules), informational counters, several types of charts, and 14 "Mission Cards", which were the SASL version of scenarios. Only German, Russian, Partisan and US forces were covered in this game, and the rulebook, Beyond Valor and Yanks were prerequisites.

A 2nd Edition was released expanding the charts to include all nationalities covered by ASL, with the exception of Axis Minors and the Finns. An expanded version of Chapter S was included and 21 Mission cards. Prerequisites for play of SASL depend on the nationalities involved.

ASL Starter Kits
In 2004, in recognition that newcomers to the ASL hobby would have a hard time learning 200 pages of rules quickly and happily, the Starter Kits were introduced. Along with the new semi-mounted mapboards replacing the older mounted style, these kits provided newcomers to ASL with everything they needed to get into the game with a minimum of reading. In a form of Programmed Instruction not possible with the ASL Rulebook, each starter kit comes with a small pamphlet outlining only the bare minimum of rules necessary for play of the game. Each kit focuses on a particular aspect of ASL.

 * 1—ASL Starter Kit 1, German, American and Russian forces, infantry, support weapons
 * 2—ASL Starter Kit 2, German, Italian, British, Allied Minor, and American forces, ordnance
 * 3—ASL Starter Kit 3, German, American, British and Russian forces, Tanks, armored cars
 * 4—ASL Starter Kit 4, Japanese and US Marine Corps units, including vehicles and ordnance.

ASL Starter Kit #1
The first Starter Kit includes very basic rules to quickly get players into a simplified version of ASL. Counters are included for German, Russian and American infantry units and is intended as a stand-alone purchase with the expectation that players who enjoy the experience will feel comfortable "graduating" to the full-blown ASL game series. In addition to counters and two geomorphic boards (this release also marked the end of expensively mounted mapboards, introducing a less durable cardboard map style), a small rules booklet, quick reference chart, and two dice are included.

ASL Starter Kit #2
The second Starter Kit adds rules for using artillery pieces, anti-tank guns, mortars and shaped-charge weapons (SCW - in ASL specifically referring to infantry carried and shoulder fired weapons like the bazooka, PIAT or Panzerschreck). This game, like the first Starter Kit, is intended as a stand-alone game and includes two infantry-only scenarios. Only what is included is necessary for play of the game, with the expectation that players who enjoy the experience will feel comfortable "graduating" to the full-blown ASL game series. In addition to counters depicting various nationalities and boards, a small 20 page rules booklet, pair of quick reference charts, and two dice are included.

(Scenarios s7 and s8 were sold separately in issues of Operations Magazine and are currently available as free downloads from MMP )

ASL Starter Kit #3
ASL Starter Kit #3 adds rules for tanks and other vehicles. It contains a comprehensive starter kit 28-page rule book, and a 12-page Historical Notes (ASL chapter H) reference for the vehicles and ordnance contained. Two dice are included.

(scenarios s17 to s19 and 28-31 are available on MMP's website as free downloads)

Decision at Elst
Decision at Elst is the first Advanced Squad Leader Starter Kit Historical Module and covers the battle at Elst, Holland, in September 1944 between British and German units during Operation MARKET-GARDEN. It contains a 28-page Advanced Squad Leader Starter Kit basic rules book and a 20-page Decision at Elst Campaign Game rules booklet.

ASL Starter Kit #4
ASL Starter Kit Module #4 PTO brings ASLSK to the Pacific Theater of Operations (PTO), and adds the Japanese and the United States Marine Corps to the ASLSK lineup. ASLSK#4 is a self-contained ASL module that gives players the opportunity to start playing Advanced Squad Leader almost immediately. Two dice are included.

The General
The General was an Avalon Hill house organ and as such, regularly promoted ASL by including in-depth articles on gameplay, "series replay" features where games were recorded and printed move for further analysis, and published scenarios. There were three main categories of ASL Scenarios printed in The General:  conversions from the original Squad Leader system, new scenarios, and tournament scenarios.

Squad Leader Conversions were lettered A-W, with the first scenarios appearing in Volume 22, Number 6 and the last in Volume 32 Number 3.

Tournament Scenarios were numbered T1 - T16, and ran between Volume 24, Number 2 and Volume 29, Number 1.

New scenarios included those for ASL (G1 - G46, Volume 23, Number 3 to Volume 32 Number 2) as well as three Deluxe ASL scenarios (DASL A - DASL C), one Historical ASL scenario, and one interesting new scenario using the map board from the Devil's Den game by Avalon Hill (a game about a battle of the American Civil War). This latter was numbered Scenario 3000. Scenario 2000 had been an SL scenario called Operation Hubertus, a "monster scenario" set in Stalingrad and apparently utilizing the research from the later module Red Barricades.

ASL Annual
Aside from regular features in The General Magazine, AH also produced a series of magazines focused on ASL but with some original SL content also, beginning in 1989. The ASL Annual was, as the name implies, released once a year, with issues in 1989, 1990, 1991 and 1992, and two issues were published in 1993 (called ASL Annual '93a and ASL Annual '93b). No issue was published in 1994, with issues again appearing in 1995, 1996 and 1997. The 1995 issue was named ASL Annual '95w (Winter) in anticipation of a second issue that year being printed in the summer, but it did not materialize. Scenarios located in the ASL Annual were numbered sequentially with an "A" prefix, either ASL Scenario A1, A2, etc., or SL Scenario A1, A2, etc., Deluxe ASL Scenario A1, A2, etc.

ASL Journal
When MMP took over publication of ASL components, they started to produce ASL Journal on a generally annual basis. Format for the magazine remained very similar to the ASL Annual, though no SL-themed content was included. with no outside advertising, and full of articles, variants, and scenarios for all incarnations of SL and ASL. New scenarios of ASL (or DASL) were given "J" numbers, while SASL scenarios were given an "r" prefix (since they utilized the Red Barricades mapsheets).

Third party products
A variety of "third party" products have been developed for ASL on an ongoing basis by a variety of publishers, including scenario packs and historical modules (including mapsheets). Two prolific "third party" publishers are Critical Hit and Heat of Battle, who have both produced scenario packs, geomorphic and historical mapsheets, and even new playing pieces. In recent years Le Franc Tireur and Bounding Fire productions have also produced a number of substantial products. Other products include player aids such as cards indicating SAN (Sniper Activation Numbers) and for resolving OBA (Off Board Artillery) battery access. There is also an English online free-to-view fanzine called View From The Trenches containing articles, reviews, and occasionally scenarios. Since 1996, Evan Sherry and the Tampa ASL Group have produced Schwerpunkt (published by Sherry Enterprises), an ASL magazine that features scenarios, scenario analyses and articles. To date, the Tampa Group has published over 200 scenarios in the pages of Schwerpunkt and its sister publication, Rally Point.

Scenario design
Two (unofficial) books on ASL scenario design have been written by ASL enthusiasts. Scenario Designers Guide was self-published by Mark Pitcavage, and Scenario Designer's Handbook was published by Michael A. Dorosh.

Early computer programs based on Avalon Hill games
While a computerized assistant for ASL was released (ASL Gamer's Assistance Program, or ASL GAP), no computerized version of the game itself has yet materialized. A similar game called Under Fire was released by Avalon Hill's computer division in 1985 but like most Avalon Hill computer games, was behind the industry standards for graphics and gameplay. It was not billed as a computer version of ASL, though it did bear some similarities in that players commanded roughly company sized forces. Only three maps were available for play. The game was released for Apple II, Commodore 64, and DOS systems. The game was unique (and rather unsatisfying to many) in that for each of the nine scenarios, victory was not declared at game's end. A results screen would show losses in men and equipment, and list possession of objectives, leaving the determination of "victory" to the player.

Approximations of a computerized version of SL/ASL was the 1981 release of Close Assault, also by Avalon Hill, which included an actual mapboard and counters that the human player used to make his moves. He would then input them into the computer for resolution of sighting and combat. Then the computer would make its move, and print only the results that the human units could see.

Though the counters were larger, they used the factors from Squad Leader. The player input the weapons and leaders directly into the game rather than using counters as in the board game.

Like the original Squad Leader board game, German, Russian and American nationalities were represented. The computer allowed three scenarios and any combination of two forces, including a hypothetical US vs USSR 1945 scenario.

The game was released for the Apple II, Atari 800, and the TRS-80.

Computer ASL interpretations
There have been a number of computer game interpretations of ASL.

Close Combat by Atomic Games was originally devised as a computer game version of ASL. Atomic Games had already developed several games for Avalon Hill, however, with Avalon Hill embroiled in a financial crisis that would ultimately lead to its demise, Atomic Games took what work they had completed, severed ties with the board game franchise and completed the game's development for Microsoft. The first three Close Combat games were notable, at the time, for being among the few games published by Microsoft. The final two games in the original series were, however, published by Strategic Simulations, Inc.

In 1998 Big Time Software negotiated with Avalon Hill to do a computerized version of Advanced Squad Leader, but plans fell through. Big Time Software went on to produce Combat Mission: Beyond Overlord, which was a 3D tactical computer game very similar to Advanced Squad Leader but with significant differences. While lacking much of the arcane detail of ASL (you could not swim, climb cliffs, or descend onto the battlefield by parachute), it also featured an innovative simultaneous turn-based system, and provided complete orders of battle for German, American, British, Canadian, Free French and Polish forces in Northwest Europe from 6 June 1944 to 8 May 1945.

Close Combat and Combat Mission both inspired later computer games which are beyond the scope of this article, including GI Combat (a 3D version of CC which also inspired Eric Young's Squad Assault and CMX2, a second-generation version of the Combat Mission game engine. None of these later offspring of CC or CM were directly related to ASL, and both series took on lives of their own.

WW2T is a 2D computer game for PC, Linux and Mac OSX based on the ASL rule set. The game has been released in 2015 and is currently in Alpha version. It can be played in hotseat mode, against another opponent in a LAN or online via a webservice. The rule set so far covers infantry and ordnance but is permanently extended. It also features a simple map and scenario editor to create your own matches. All ASL rules are fully validated by the game engine so new players without extended knowledge of the game rules should be able to play more rapidly.

Avalon Hill's Squad Leader
Hasbro eventually permitted the release of a game called Avalon Hill's Squad Leader  The game, released by MicroProse in 2000 (but developed by Random Games), bore no resemblance to either Squad Leader or Advanced Squad Leader, was well behind industry standards in terms of graphics and gameplay, had an awkward interface and was on a completely different scale than the actual SL and ASL games.

Virtual Advanced Squad Leader
The most successful literal adaptation of ASL to the computer has been Virtual Advanced Squad Leader, designed by Rodney Kinney as described above. VASL still officially requires ownership of the physical components of the games, however, or at least of the printed scenario cards, reference cards, and rulebook. In addition to possession of these physical components, a detailed understanding of the rules must be expected of players, as the computer version does not enforce rules - it merely serves as a means of manipulating 2-dimensional virtual game boards and pieces in an online environment facilitating long distance play, either by email or in real time. The closest the game comes to performing any of the "chores" of playing ASL is by providing random dice roll results for both players and recording moves from hex to hex on the mapboards. Some LOS calculations can also be made by the computer engine.

Reviews

 * Casus Belli #32 (Apr 1986)

title: Advanced Squad Leader


text:
User:Dwindrim~enwiki/graphics

Graphics Gallery

title: User:Dwindrim~enwiki/graphics


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Chyle

Chyle (from the Greek word χυλός chylos, "juice" ) is a milky bodily fluid consisting of lymph and emulsified fats, or free fatty acids (FFAs). It is formed in the small intestine during digestion of fatty foods, and taken up by lymph vessels specifically known as lacteals. The lipids in the chyle are colloidally suspended in chylomicrons.

Clinical significance
A chyle fistula occurs when defect(s) of lymphatic vessel(s) result in leakage of lymphatic fluid, typically accumulating in the thoracic (pleural) or abdominal (peritoneal) cavities, leading to a chylous pleural effusion (chylothorax) or chylous ascites, respectively.

Diagnosis of a chyle fistula may be accomplished by analysis of pleural/peritoneal fluid. Identifying the source (localizing the lymphatic defect) is often challenging, but may be accomplished with lymphangiography, which is occasionally associated with a serendipitous therapeutic effect (resolution of the leak), thought to be secondary to a sclerosant effect of the lymphangiography contrast.

Due to the extreme friability of the lymphatic vessels, direct repair of defects is impractical. Therefore, treatment of chyle fistulae relies upon either decreased production of lymphatic fluid to allow for healing of lymphatic defect(s) or permanent diversion of lymphatic fluid away from lymphatic defect(s). Decreased production of lymphatic fluid may be accomplished by dietary restriction (or complete replacement of oral intake with total parenteral nutrition), as well as by the medications octreotide (a synthetic analogue of the hormone somatostatin) and orlistat (a lipase inhibitor that decreases absorption of dietary fats). Permanent diversion of lymphatic fluid may be accomplished by thoracic duct embolization (a needle-based procedure to occlude the duct by depositing glue/embolic material into it) or by thoracic duct ligation (an open surgical procedure to occlude the duct by suturing tightly around it).

title: Chyle


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Storyline

Storyline may refer to:
 * The plot or subplot of a story
 * The narrative of a work, whether of fictional or nonfictional basis
 * The narrative threads experienced by each character or set of characters in a work of fiction
 * The storyline method of teaching
 * Alternative term for an angle in professional wrestling – see Glossary of professional wrestling terms: Angle

Music

 * Storyline (Raphe Malik album), 2000
 * Story Line, 1991 album by Lorie Line
 * Storyline, 2005 album by Mari Wilson
 * Storyline (Hunter Hayes album), 2014

title: Storyline