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Battle of Chosin Reservoir

The Battle of Chosin Reservoir, also known as the Chosin Reservoir Campaign or the Battle of Lake Changjin, was an important battle in the Korean War. The name "Chosin" is derived from the Japanese pronunciation "Chōshin, instead of the Korean pronunciation.

The battle took place about a month after the People's Republic of China entered the conflict and sent the People's Volunteer Army (PVA) 9th Corps to infiltrate the northeastern part of North Korea. On 27 November 1950, the Chinese force surprised the US X Corps commanded by Major General Edward Almond in the Chosin Reservoir area. A brutal 17-day battle in freezing weather soon followed. Between 27 November and 13 December, 30,000 United Nations Command troops, later nicknamed "The Chosin Few", under the field command of Major General Oliver P. Smith were encircled and attacked by about 120,000 Chinese troops under the command of Song Shilun, who had been ordered by Mao Zedong to destroy the UN forces.

The UN forces were nevertheless able to break out of the encirclement and withdraw to the port of Hungnam. Both sides suffered heavy casualties, especially the Chinese, with both battle casualties and non-battle casualties caused by the frigid weather. The withdrawal of the US Eighth Army from northwest Korea in the aftermath of the Battle of the Ch'ongch'on River and the evacuation of the X Corps from the port of Hungnam in northeast Korea marked the complete withdrawal of UN troops from North Korea.

Background

By mid-October 1950, after the successful landing at Inchon by the US X Corps, the Eighth Army breakout from the Pusan Perimeter and the subsequent pursuit and destruction of the Korean People's Army (KPA), the Korean War appeared to be all but over. United Nations (UN) forces advanced rapidly into North Korea with the intention of reuniting North and South Korea before the end of 1950. North Korea is divided through the center by the impassable Taebaek Mountains, which separated the UN forces into two groups. The US Eighth Army advanced north through the western coast of the Korean Peninsula, while the Republic of Korea (ROK) I Corps and the US X Corps advanced north on the eastern coast.

At the same time the People's Republic of China entered the conflict after issuing several warnings to the United Nations. On 19 October 1950, large formations of Chinese troops, dubbed the People's Volunteer Army (PVA), secretly crossed the border and into North Korea. One of the first Chinese units to reach the Chosin Reservoir area was the PVA 42nd Army, which was tasked with stopping the eastern UN advances. On 25 October, the advancing ROK I Corps made contact with the Chinese and halted at Funchilin Pass (40.204°N, 127.3°W), south of the Chosin Reservoir.

After the landing at Wonsan, the US 1st Marine Division of the X Corps engaged the defending PVA 124th Division on 2 November; the ensuing battle caused heavy casualties among the Chinese. On 6 November, the PVA 42nd Corps ordered a retreat to the north with the intention of luring the UN forces into the Chosin Reservoir. By 24 November, the 1st Marine Division occupied both Sinhung-ni (40.557°N, 127.27°W) on the eastern side of the reservoir and Yudami-ni (40.48°N, 127.112°W) on the west side.

Faced with the sudden attacks by Chinese forces in the Eighth Army sector, General Douglas MacArthur ordered the Eighth Army to launch the Home-by-Christmas Offensive. To support the offensive, MacArthur ordered the X Corps to attack west from the Chosin Reservoir and to cut the vital Manpojin—Kanggye—Huichon supply line. In response, Major General Edward M. Almond, commander of the US X Corps, formulated a plan on 21 November. It called for the US 1st Marine Division to advance west through Yudami-ni, while the US 7th Infantry Division would provide a regimental combat team to protect the right flank at Sinhung-ni. The US 3rd Infantry Division would also protect the left flank, while providing security in the rear area. By then the X Corps was stretched thin along a 400-mile front.

Surprised by the Marine landing at Wonsan, Chinese Communist Party chairman Mao Zedong called for the immediate destruction of the ROK Capital Division, ROK 3rd Infantry Division, US 1st Marine Division, and US 7th Infantry Division in a telegram to Commander Song Shilun of the PVA 9th Corps on 31 October. Under Mao's urgent orders, the 9th Corps was rushed into North Korea on 10 November. Undetected by UN intelligence, it entered the Chosin Reservoir area on 17 November, with the 20th Army of the 9th Corps relieving the 42nd Army near Yudami-ni.

Location, terrain and weather
Chosin Reservoir is a man-made lake located in the northeast of the Korean peninsula. The name Chosin is the Japanese pronunciation of the Korean place name Changjin, and the name stuck due to the outdated Japanese maps used by UN forces. The battle's main focus was around the 78 mi road that connects Hungnam and Chosin Reservoir, which served as the only retreat route for the UN forces. Through these roads, Yudami-ni and Sinhung-ni, located at the west and east side of the reservoir respectively, are connected at Hagaru-ri (now Changjin-ŭp) (40.3838°N, 127.249°W). From there, the road passes through Koto-ri (40.284°N, 127.3°W) and eventually leads to the port of Hungnam. The area around the Chosin Reservoir was sparsely populated.

The battle was fought over some of the roughest terrain during some of the harshest winter weather conditions of the Korean War. The road was created by cutting through the hilly terrain of Korea, with steep climbs and drops. Dominant peaks, such as the Funchilin Pass and the Toktong Pass (40.3938°N, 127.161°W), overlook the entire length of the road. The road's quality was poor, and in some places it was reduced to a one-lane gravel trail. On 14 November 1950, a cold front from Siberia descended over the Chosin Reservoir, and the temperature plunged, according to estimates, to as low as -36 °F. The cold weather created considerable danger of frostbite casualties and was accompanied by frozen ground, icy roads, and weapon malfunctions. Medical supplies froze; morphine syrettes had to be defrosted in a medic's mouth before they could be injected; blood plasma was frozen and useless on the battlefield. Even cutting off clothing to deal with a wound risked gangrene and frostbite. Batteries used for the Jeeps and radios did not function properly in the temperature and quickly ran down. The lubrication in the guns gelled and rendered them useless in battle. Likewise, the springs on the firing pins would not strike hard enough to fire the round, or would jam.

Forces and strategies

Although the 1st Marine Division landed at Wonsan as part of Almond's US X Corps, Almond and Major General Oliver P. Smith of the 1st Marine Division shared a mutual loathing of each other that dated back to a meeting before the landing at Inchon, when Almond had spoken of how easy amphibious landings are even though he had never been involved in one. Smith believed there were large numbers of Chinese forces in North Korea despite the fact that higher headquarters in Tokyo said otherwise, but Almond felt Smith was overly cautious. The mutual distrust between the commanders caused Smith to slow the 1st Marine Division's advance towards the Chosin Reservoir in violation of Almond's instructions. Smith established supply points and airfields along the way at Hagaru-ri and Koto-ri.

As the US X Corps was pushing towards the reservoir, the Chinese formulated their strategy, based on their experiences in the Chinese Civil War. Working from the assumption that only a light UN presence would be at the reservoir, the Chinese 9th Corps was first to destroy the UN garrisons at Yudami-ni and Sinhung-ni, then push towards Hagaru-ri. Believing the bulk of the US X Corps would move to rescue the destroyed units, the 9th Corps would then block and trap the main UN forces on the road between Hagaru-ri and Hungnam. The 9th Corps initially committed eight divisions for the battle, with most of the forces concentrated at Yudami-ni and Sinhung-ni.

The flaw in the Chinese plan was a lack of accurate intelligence about the UN forces. Even though the US X Corps was stretched thin over northeast Korea, the slow Marine advance allowed the bulk of the US 1st Marine Division, including the 5th, 7th and 11th Marines, to be concentrated at Yudami-ni. Furthermore, the strategically important Hagaru-ri, where a C-47-capable airfield was under construction and a supply dump, was not a priority for the Chinese despite being lightly defended by the 1st and 7th Marines. Only Regimental Combat Team 31 (RCT-31), an understrength and hastily formed regimental combat team of the US 7th Infantry Division, was thinly spread along the eastern bank of the reservoir. Those units later took the brunt of the Chinese assaults.

As for the UN forces, the 1st Marine Division had an effective strength of 25,473 men at the start of the battle, and it was further reinforced by the British Royal Marines unit 41 (Independent) Commando and the equivalent of two regiments from the 3rd and 7th Army Infantry Divisions. The UN forces had a combined strength of about 30,000 men during the course of the battle. The UN forces at Chosin were also supported by one of the greatest concentrations of air power during the Korean War, since the 1st Marine Aircraft Wing stationed at Yonpo Airfield and five aircraft carriers from the US Navy's Task Force 77 were able to launch 230 sorties daily to provide close air support during the battle, while the US Air Force Far East Combat Cargo Command in Japan reached the capacity of airdropping 250 tons of supplies per day to resupply the trapped UN forces.

Although the 9th Corps was one of China's elite formations, composed of veterans and former POWs from the Huaihai Campaign, several deficiencies hampered its ability during the battle. Initially the 9th Corps was intended to be outfitted in Manchuria during November, but Mao suddenly ordered it into Korea before that could happen. As a result, the 9th Corps had almost no winter clothing for the harsh Korean winter. Similarly, poor logistics forced the 9th Corps to abandon heavy artillery, while working with little food and ammunition. The food shortage forced the 9th Corps to initially station a third of its strength away from the Chosin Reservoir in reserve, and starvation and exposure weakened the Chinese units, since foraging was not an option in the sparsely populated area. By the end of the battle, more Chinese troops had died from the cold than from combat and air raids.

Chinese strength is usually estimated at 120,000 troops for the battle. Before arriving in Korea, the 9th Corps was also reinforced. Each of its three corps had four divisions instead of the regular three; thus it had 12 divisions, with 10,000 men per division. Infantry from two formerly "liberated" (surrendered) Nationalist divisions were absorbed to bring each infantry company up to strength. Some companies had approximately 150 men, while others were reinforced with more than 200 men. However, attrition due to UN air raids, poor logistics and cold weather had also taken a toll on the way to the battlefield. On the day 9th Corps entered Korea, for example, frostbite inflicted 700 casualties, while most of its transport vehicles were destroyed by UN air raids. During the course of the battle, Chinese prisoners of war reported that most of the 9th Corps’ divisions had become under strength, numbering about 6,500 to 7,000 men per division. These factors, plus uncertainties over the Chinese order of battle in Western sources, led some historians to revise Chinese numbers down to as low as 60,000 during the course of battle.

Eventually, all 12 Chinese divisions of the 9th Corps were deployed, although the 78th and the 88th Divisions of the PVA 26th Army did not make contact with UN forces during the course of the battle. Eight divisions of the PVA 20th and 27th Armies served as the main attacking force. Four divisions of the PVA 26th Army initially were held back in reserve, and deployed after 20th and 27th Armies had exhausted all their available strength.

Battle
On the night of 27 November, the PVA 20th and 27th Armies of the 9th Corps launched multiple attacks and ambushes along the road between the Chosin Reservoir and Kot'o-ri. At Yudam-ni, the 5th, 7th and 11th Marines were surrounded and attacked by the PVA 79th and 89th Divisions, with the 59th Division attacking the road between Yudam-ni and Hagaru-ri to cut off communication. Similarly, RCT-31 was isolated and ambushed at Sinhung-ni by the PVA 80th and 81st Divisions. At Hagaru-ri, the 1st Marine Division command headquarters was targeted by the PVA 58th Division. Finally, the PVA 60th Division surrounded elements of the 1st Marines at Kot'o-ri from the north. Caught by complete surprise, the UN forces were cut off at Yudam-ni, Sinhung-ni, Hagaru-ri and Kot'o-ri by 28 November.

Actions at Yudam-ni
Acting on Almond's order, Smith ordered the 5th Marines to attack west toward Mupyong-ni on 27 November. The attack was soon stalled by the PVA 89th Division and forced the Marines to dig in on the ridges surrounding Yudam-ni. As night came, three Chinese regiments of the 79th Division attacked the ridges on the north and northwest of Yudam-ni, hoping to annihilate the garrison in one stroke. Close quarters fighting soon developed as the attackers infiltrated Marine positions, but the 5th and 7th Marines held the line while inflicting heavy casualties on the Chinese. As day broke on 28 November, the Chinese and Americans were locked in a stalemate around the Yudam-ni perimeter.

While the battle was underway at Yudam-ni, the PVA 59th Division blocked the road between Yudam-ni and Hagaru-ri by attacking the defending Charlie and Fox Companies of the 7th Marines. The successful assault forced Charlie Company to retreat into Yudam-ni, which left Fox Company, commanded by Captain William E. Barber, isolated on a hill overlooking the Toktong Pass, a vital pass that controlled the road. On 29 November, several efforts by the 7th Marines failed to rescue Fox Company, despite inflicting heavy casualties on the Chinese. Aided by artillery from Hagaru-ri and Marine Corsair fighters, Fox Company managed to hold out for five days while enduring constant attacks by the PVA 59th Division.

After the heavy losses suffered by the PVA 79th Division at Yudam-ni, 9th Corps headquarter realized that the bulk of the 1st Marine Division was stationed at Yudam-ni, with a garrison strength double the initial estimate. Believing that any further assaults would be futile, Song Shilun ordered the 9th Corps to switch their main attacks toward Sinhung-ni and Hagaru-ri, leaving Yudam-ni alone from 28 to 30 November. At the same time, the US Eighth Army on the Korean western front was forced into full retreat at the Battle of the Ch'ongch'on River, and MacArthur ordered Almond to withdraw the US X Corps to the port of Hungnam. Acting on Almond and Smith's instructions, Lieutenant Colonel Raymond L. Murray and Colonel Homer L. Litzenberg, commanders of the 5th and 7th Marines, respectively, issued a joint order to break out from Yudam-ni to Hagaru-ri on 30 November. Faced with tough fighting between the blocking Chinese divisions and the withdrawing Marines, Smith remarked: "Retreat, hell! We're not retreating, we're just advancing in a different direction."

For the breakout, the Marines formed into a convoy with a single M4A3 Sherman tank in the lead. The plan was to have 3rd Battalion, 5th Marines (3/5) as the vanguard of the convoy, with three battalions covering the rear. At the same time, 1st Battalion, 7th Marines (1/7) would attack towards Fox Company in order to open the road at Toktong Pass. To start the breakout, 3rd Battalion, 7th Marines (3/7) had to first attack south and capture Hills 1542 and 1419 in order to cover the road from Chinese attacks. The breakout was carried out under the air cover of the 1st Marine Air Wing.

On the morning of 1 December, 3/7 Marines engaged the PVA 175th Regiment of the 59th Division at Hills 1542 (40.435°N, 127.107°W) and 1419 (40.428°N, 127.135°W). The Chinese defenders soon forced the Marines to dig in on the slopes between the road and the peaks when the convoy passed 3/7's position by the afternoon. With Hagaru-ri still not captured, the PVA High Command scrambled the 79th Division to resume attacks on Yudam-ni, while the 89th Division rushed south towards Kot'o-ri. The Chinese struck at night, and the ferocity of the fighting forced the rear covering forces to call in night fighters to suppress the attacks. The fighting lasted well into the morning of 2 December until all the Marines had managed to withdraw from Yudam-ni.

At the same time, 1/7 Marines also tried to break the Chinese blockade at Hill 1419 on 1 December. Despite being badly reduced by combat, hunger and frostbite, the PVA 59th Division sent in its last five platoons and refused to yield. As night approached, 1/7 finally captured the peak and started to march through the hills on the east side of the road. Relying on the element of surprise, they managed to destroy several Chinese positions along the road. On the morning of 2 December, a joint attack by Fox Company and 1/7 secured the Toktong Pass, thus opening the road between Yudam-ni and Hagaru-ri.

Although the road had been opened between Yudam-ni and Hagaru-ri, the convoy still had to fight through the numerous Chinese positions on the hills overlooking the road. On the first night of the retreat, the Chinese struck the convoy in force and inflicted heavy casualties on 3/5 Marines. Although strong air cover suppressed most of the Chinese forces for the rest of the march, the cold weather, harassing fire, raiding parties, and roadblocks slowed the retreat to a crawl, while inflicting numerous casualties. Despite those difficulties, the convoy reached Hagaru-ri in an orderly fashion on the afternoon of 3 December, with the withdrawal completed on 4 December.

East of the reservoir
RCT-31, later known as "Task Force Faith," was a hastily formed regimental combat team from the 7th Infantry Division that guarded the right flank of the Marine advance towards Mupyong-ni. Before the battle, RCT-31 was spread thin, with main elements separated on the hills north of Sinhung-ni, the Pyungnyuri Inlet west of Sinhung-ni, and the town of Hudong-ni (40.43°N, 127.28°W) south of Sinhung-ni. Although the Chinese believed RCT-31 to be a reinforced regiment, the task force was actually understrength, with one battalion missing, due to the bulk of the 7th Infantry Division being scattered over northeast Korea.

On the night of 27 November, three regiments from the 80th Division attacked the northern hills (40.489°N, 127.259°W) and the inlet, completely surprising the defenders. The 1st Battalion, 32nd Infantry, to the north of Sinhung-ni suffered heavy casualties, while the 57th Field Artillery Battalion and the 3rd Battalion, 31st Infantry, were almost overrun at Pyungnyuri Inlet. The Chinese also sent the 242nd Regiment of the 81st Division towards Hill 1221, (40.449°N, 127.268°W), an undefended hill that controlled the road between Sinhung-ni and Hudong-ni. As the night's fighting ended, RCT-31 was split into three elements.

Believing that the defenders had been completely destroyed at the inlet, the Chinese stopped their attacks and proceeded to loot the American positions for food and clothing. As morning came on 28 November, the 3/31st Infantry counterattacked the PVA 239th Regiment at the inlet, driving the surprised Chinese back in a complete rout. In the afternoon, Almond flew into the Sinhung-ni perimeter of RCT-31, convinced that RCT-31 was strong enough to begin its attack north and deal with whatever "remnants" of Chinese forces were in their way. Almond ordered Colonel Allan D. Maclean, the commander of RCT-31, to resume the offensive north, while presenting Silver Stars to three of Maclean's officers. In disgust, Lieutenant Colonel Don C. Faith, Jr., the commander of the 1/32nd Infantry, threw his medal into the snow.

On the night of 28 November, the PVA 80th Division attacked again with four regiments. At the inlet, the Chinese assault became a disaster as communications broke down, while devastating fire from the M16 and M19 anti-aircraft (AA) guns attached to the 57th Field Artillery Battalion swept the Chinese ranks. In the aftermath, the PVA 238th and the 239th Regiment together had fewer than 600 soldiers. The attacks by PVA 240th Regiment, on the other hand, forced Maclean to order a retreat from the northern hills towards Sinhung-ni. On 29 November, the 1st Battalion managed to break through the Chinese blockade and reached the Sinhung-ni perimeter, but Maclean was lost when he mistook some Chinese soldiers for American. The Chinese finally stopped their attacks on the night of 29 November, while waiting for fresh reinforcements.

While RCT-31 was under siege, Almond finally instructed the 1st Marine Division to rescue it by breaking out of Yudam-ni, an impossible order for Smith to implement. Only the 31st Tank Company tried to rescue RCT-31, by attacking Hill 1221 from Hudong-ni, but without infantry support, the two armored attacks on 28 and 29 November were stalled by slippery roads, rough terrain, and close infantry assaults. By 30 November, the US forces evacuated Hudong-ni in order to defend Hagaru-ri, leaving the rest of RCT-31 completely isolated.

On 30 November, Major General David G. Barr, the commander of the 7th Infantry Division, flew into Sinhung-ni and met with Faith, who by now had assumed command of RCT-31. Faith laid out the difficulties of a breakout, particularly the 500 wounded that RCT-31 had to bring along. On the same day, parts of the PVA 94th Division and the rest of the 81st Division arrived as reinforcements for the 80th Division. By midnight, six Chinese regiments renewed their attacks, and Zhan Danan, the commander of the 80th Division, ordered the complete destruction of RCT-31 before dawn. Again, the 57th Battalion's AA guns held the Chinese at bay, but supplies of shells were desperately low. On the day of 1 December, Faith finally ordered RCT-31 to break out from Sinhung-ni and withdraw to Hagaru-ri.

The breakout began as soon as the weather allowed the 1st Marine Aircraft Wing to provide air cover on 1 December. As the soldiers formed a convoy and tried to leave the Sudong-ni perimeter, the PVA 241st Regiment immediately swarmed over the American forces, with three other regiments closing in. Left with no choice, the covering aircraft dropped napalm right in front of RCT-31, inflicting casualties on both American and Chinese troops. The resulting firestorm wiped out the blocking Chinese company, allowing the convoy to advance. As the front of RCT-31 made its way forward, heavy small arms fire caused many members of the rear guard to seek shelter below the road instead of protecting the trucks. Chinese fire also killed or wounded those already in the trucks as well as the drivers, who viewed the job as a form of suicide. Slowly, the convoy approached a roadblock under Hill 1221 in the late afternoon. Several parties tried to clear Hill 1221, but after taking part of the hill, the leaderless soldiers continued out onto the frozen reservoir instead of returning to the column. As Faith led an assault on the roadblock, he was hit by a Chinese grenade and subsequently died of his wounds. The convoy managed to fight past the first roadblock, but as it reached the second at Hudong-ni, RCT-31 disintegrated under Chinese attacks. Out of the original 2,500 soldiers, about 1,050 managed to reach Hagaru-ri, and only 385 survivors were deemed able-bodied. The remnants of RCT-31 were formed into a provisional army battalion for the rest of the battle.

Actions at Hagaru-ri
To support the Marine attack towards Mupyong-ni, Hagaru-ri became an important supply dump with an airfield under construction. Smith and 1st Marine Division headquarters were also located at Hagaru-ri. With the bulk of the 1st Marine Division gathered at Yudam-ni, Hagaru-ri was lightly defended by two battalions from the 1st and 7th Marines, the rest of the garrison being composed of engineers and rear support units from both the Army and the Marine Corps.

The original Chinese plan called for the 58th Division to attack Hagaru-ri on the night of 27 November, but the division became lost in the countryside due to the outdated Japanese maps it used. It was not until the dawn of 28 November that the 58th Division arrived at Hagaru-ri. Meanwhile, from the fighting and ambushes that had occurred the previous night, the garrison at Hagaru-ri noticed the Chinese forces around them. Lieutenant Colonel Thomas L. Ridge, commander of 3rd Battalion, 1st Marines (3/1), predicted the Chinese attack would come on the night of 28 November. Almost everyone, including rear support units with little combat training, was pressed into service on the front line due to the manpower shortage, and the entire perimeter was on full alert by 21:30.

It was not long before the PVA 173rd Regiment attacked the western and the southern perimeter, while the 172nd Regiment struck the hills on the northern perimeter. Despite the preparations, the understrength garrison was overwhelmed, with the Chinese opening several gaps in the defenses and reaching the rear areas. The resulting chaos, however, caused a breakdown in discipline among the Chinese soldiers, who began looting food and clothing instead of exploiting the situation. The defending Americans managed to destroy the Chinese forces in counterattacks, while a breakdown of communications between the Chinese regiments allowed the gaps to close. When the fighting stopped, the Chinese had only gained the East Hill (40.387°N, 127.259°W) on the northern perimeter. Another attack was planned for the night of 29 November, but air raids by VMF-542 broke up the Chinese formations before it could be carried out.

Given the critical manpower shortage at Hagaru-ri, on 29 November, Smith ordered Colonel Lewis "Chesty" Puller of the First Marine Regiment to assemble a task force to be sent north from Kot'o-ri to open the road south of Hagaru-ri. A task force was formed with 921 troops from 41 (Royal Marine) Commando, G Company of the 1st Marines and B Company of the 31st Infantry. It was dubbed "Task Force Drysdale" after its commander, Lieutenant Colonel Douglas B. Drysdale, who also commanded 41 Commando.

On the afternoon of 29 November, Task Force Drysdale pushed north from Koto-ri, while under constant attack from the PVA 60th Division. The task force's harrowing experience later earned the road the nickname "Hell Fire Valley". As the Chinese attacks dragged on, the task force became disorganized, and a destroyed truck in the convoy later split the task force into two segments. Although the lead segment fought its way into Hagaru-ri on the night of 29 November, the rear segment was destroyed. Despite suffering 162 dead and missing and 159 wounded, the task force managed to bring in 300 badly needed infantrymen for the defense at Hagaru-ri.

As more reinforcements arrived from Hudong-ni on 30 November, the garrisons attempted to recapture the East Hill. All efforts failed, despite the destruction of a Chinese company. When darkness settled, the PVA 58th Division gathered its remaining 1,500 soldiers in a last-ditch attempt to capture Hagaru-ri. The reinforced defenders annihilated most of the attacking forces, with only the defences around the East Hill giving way. As the Chinese tried to advance from the East Hill, they were cut down by the 31st Tank Company.

By 1 December, the PVA 58th Division was virtually destroyed, with the remainder waiting for reinforcements from the 26th Army of the 9th Corps. Much to the frustration of Song Shilun, the 26th Corps did not arrive before the Marines broke out of Yudam-ni. The airfield was opened to traffic on 1 December, allowing UN forces to bring in reinforcements and to evacuate the dead and wounded. With the Marines at Yudam-ni completing their withdrawal on 4 December, the trapped UN forces could finally start their breakout towards the port of Hungnam.

Breakout
After a short rest, the breakout began on 6 December, with the 7th Marines as the vanguard of the retreating column, while the 5th Marines covered the rear. At the same time, the much-delayed PVA 26th Army arrived at Hagaru-ri with its 76th and 77th Divisions to relieve the 58th and 60th Divisions. As the 7th Marines pushed aside the PVA 76th Division south of Hagaru-ri, the 5th Marines took over the Hagaru-ri perimeter and recaptured the East Hill from the 76th Division. In a last effort to stop the breakout, the customary Chinese night attack was launched, with the 76th and 77th Division striking the Hagaru-ri perimeter from all directions. The Marines repulsed the attacks, inflicting heavy casualties.

Meanwhile, the 7th Marines opened the road between Hagaru-ri and Koto-ri by capturing the high ground surrounding the road. But as soon as the Marines pulled out, the 77th Division returned to the peaks and attacked the column. Chaotic fighting broke out and the retreat was slowed to a crawl. The Marine night fighters returned to subdue the Chinese forces, and most of the blocking troops were eliminated. On 7 December, the rest of the column managed to reach Kot'o-ri with little difficulty, with the last elements reaching Kot'o-ri that night.

After the failure of the 26th Corps at Hagaru-ri, the PVA High Command ordered the 26th and 27th Corps to chase the escaping UN force, with the 20th Corps assigned to block the escape route. But with most of the 20th Corps destroyed at Yudam-ni and Hagaru-ri, the only forces between Kot'o-ri and Hungnam were the remnants of the 58th and 60th Divisions. In desperation, Song Shilun ordered these troops to dig in at Funchilin Pass, while blowing up the vital bridge (40.232°N, 127.296°W), hoping the terrain and obstacles would allow the 26th and 27th Corps to catch up with the retreating UN forces.

The PVA 180th Regiment that occupied Hill 1081 (40.233°N, 127.326°W) blew up the original concrete bridge and two improvised replacements in succession, believing the bridge was rendered irreparable. In response, the 1st Battalion, 1st Marines (1/1) attacked Hill 1081 from the south, and the hill was captured on 9 December, though the defenders fought to the last man. At the same time, the 7th Marines and RCT-31 attacked the bridge from the north, only to encounter defenders who were already frozen in their foxholes.

With the path to Hungnam blocked at Funchilin Pass, eight C-119 Flying Boxcars flown by the US 314th Troop Carrier Wing were used to drop portable bridge sections by parachute. The bridge, consisting of eight separate 18 ft long, 2900 lb sections, was dropped one section at a time, using a 48 ft parachute on each section. Four of these sections, together with additional wooden extensions were successfully reassembled into a replacement bridge by Marine Corps combat engineers and the US Army 58th Engineer Treadway Bridge Company on 9 December, enabling UN forces to proceed. Outmaneuvered, the PVA 58th and 60th Divisions still tried to slow the UN advance with ambushes and raids, but after weeks of non-stop fighting, the two Chinese divisions combined had only 200 soldiers left. The last UN forces left Funchilin Pass by 11 December.

One of the last engagements during the withdrawal was an ambush at Sudong (40.17°N, 127.324°W) by the pursuing PVA 89th Division, which Task Force Dog of the 3rd Infantry Division repulsed with little difficulty. The trapped UN forces finally reached the Hungnam perimeter by 21:00 on 11 December.

Evacuation at Hungnam
By the time the UN forces arrived at Hungnam, MacArthur had already ordered the evacuation of the US X Corps on 8 December in order to reinforce the US Eighth Army, which by then was badly depleted and retreating rapidly towards the 38th parallel. Following his orders, the ROK I Corps, the ROK 1st Marine Regiment and the US 3rd and 7th Infantry Divisions had also set up defensive positions around the port. Some skirmishes broke out between the defending US 7th, 17th and 65th Infantry and the pursuing PVA 27th Corps, but against the strong naval gun fire support provided by US Navy Task Force 90, the badly mauled 9th Corps was in no shape to approach the Hungnam perimeter.

In what US historians called the "greatest evacuation movement by sea in US military history", a 193-ship armada assembled at the port and evacuated not only the UN troops, but also their heavy equipment and roughly a third of the Korean refugees. One Victory ship, the SS Meredith Victory, evacuated 14,000 refugees by herself, despite being designed to carry only 12 passengers. The last UN unit left at 14:36 on 24 December, and the port was destroyed to deny its use to the Chinese. The PVA 27th Army entered Hungnam on the morning of 25 December.

Casualties
The US X Corps and the ROK I Corps reported a total of 10,495 battle casualties: 4,385 US Marines, 3,163 US Army personnel, 2,812 South Koreans attached to American formations and 78 British Royal Marines. The 1st Marine Division also reported 7,338 non-battle casualties due to the cold weather, adding up to a total of 17,833 casualties. Despite the losses, the US X Corps preserved much of its strength. About 105,000 soldiers, 98,000 civilians, 17,500 vehicles, and 350,000 tons of supplies were shipped from Hungnam to Pusan, and they later rejoined the war effort in Korea. Commanding General Smith was credited for saving the US X Corps from destruction, while the 1st Marine Division, 41 (Royal Marine) Commando and RCT-31 were awarded the Presidential Unit Citation for their tenacity during the battle. Fourteen Marines, two soldiers and one Navy pilot received the Medal of Honor, and all of the UN troops that served at Chosin were later nicknamed "The Chosin Few".

According to official estimates by the People's Liberation Army General Logistics Department published in 1988, the PVA 9th Corps suffered 21,366 combat casualties, including 7,304 killed. In addition, 30,732 non-combat casualties were attributed to the harsh Korean winter and lack of food. Total casualties thus amounted to 52,098 - more than one third of its total strength. Outside of official channels, the estimation of Chinese casualties has been described as high as 60,000 by Patrick C. Roe, the chairman of Chosin Few Historical Committee, citing the number of replacements requested by 9th Corps in the aftermath of the battle. Regardless of the varying estimates, historian Yan Xue of PLA National Defence University noted that the 9th Corps was put out of action for three months. With the absence of 9th Corps the Chinese order of battle in Korea was reduced to 18 infantry divisions by 31 December 1950, as opposed to the 30 infantry divisions present on 16 November 1950.

Operation Glory
During the battle, UN dead were buried at temporary grave sites along the road. Operation Glory took place from July to November 1954, during which the dead of each side were exchanged. The remains of 4,167 US soldiers were exchanged for 13,528 North Korean and Chinese dead. In addition, 546 civilians who died in UN prisoner-of-war camps were turned over to the South Korean government. After Operation Glory, 416 Korean War "unknowns" were buried in the National Memorial Cemetery of the Pacific, the "Punchbowl Cemetery" in Honolulu, Hawaii. According to a Defense Prisoner of War/Missing Personnel Office (DPMO) white paper, 1,394 names were also transmitted from the Chinese and North Koreans during the operation, of which 858 proved to be correct.

The 4,167 returned remains were found to be 4,219 individuals, of whom 2,944 were found to be Americans, with all but 416 identified by name. Of the 239 Korean War unaccounted for, 186 are not associated with the Punchbowl Cemetery unknowns. From 1990 to 1994, North Korea excavated and returned more than 208 sets of remains, which possibly include 200 to 400 US servicemen, but very few have been identified due to the co-mingling of remains. From 2001 to 2005, more remains were recovered from the Chosin Battle site, and around 220 were recovered near the Chinese border between 1996 and 2006.

Outcome assessment
Roy E. Appleman, the author of US Army official history South to Naktong, North to Yalu, writes that both sides could claim victory: the PVA 9th Corps ultimately held the battlefield, while X Corps held off the PVA 9th Corps in a series of battles that enabled it to withdraw most of its forces as an effective tactical unit. Allan R. Millett qualifies his assessment of the battle as a Chinese "geographic victory" in that they ejected X Corps from North Korea with the PVA’s tactical failure of achieving their stated objective of destroying the 1st Marine Division, adding that the campaign gave the UN confidence that it could withstand the superior numbers of the Chinese forces. The official Chinese history, published by PLA Academy of Military Science, states that despite the heavy casualties, the PVA 9th Corps had earned its victory by successfully protecting the eastern flank of Chinese forces in Korea, while inflicting over 10,000 casualties to the UN forces.

Eliot A. Cohen writes that the retreat from Chosin was a UN victory which inflicted such heavy losses on the PVA 9th Corps that it was put out of action until March 1951. Paul M. Edwards, founder of the Center for the Study of the Korean War, draws parallels between the battle at Chosin and the Dunkirk evacuation. He writes that the retreat from Chosin following a "massive strategic victory" by the Chinese has been represented as "a moment of heroic history" for the UN forces. Appleman, on the other hand, questioned the necessity of a sea-borne evacuation to preserve the UN forces, asserting that X Corps had the strength to break out of the Chinese encirclement at Hungnam at the end of the battle. Chinese historian Li Xiaobing acknowledges X Corps' successful withdrawal from North Korea, and writes that the Battle of Chosin "has become a part of Marine lore, but it was still a retreat, not a victory." Bruce Cumings simply refers to the battle as a "terrible defeat" for the Americans.

Patrick C. Roe, who served as an intelligence officer with the 7th Marine Regiment at Chosin, asserts that X Corps directly allowed the Eighth Army to hold the south and quoted MacArthur in corroborating his view. Yu Bin, a historian and a former member of the Chinese People's Liberation Army, states that while the destruction of Task Force Faith was viewed as the single greatest Chinese victory of the war, ultimately the PVA 9th Corps had become "a giant hospital" while failing to destroy the numerically inferior UN forces at Chosin as planned. Zhang Renchu, whose 26th Army was blamed for allowing the X Corps to escape, had threatened suicide over the outcome, while Song Shilun offered to resign his post.

The battle exacerbated inter-service hostility, the Marines blaming the US Army and its leadership for the failure. The collapse of the army units fighting on the east of the reservoir was regarded as shameful, and for many years afterwards their role in the battle was largely ignored. Later studies concluded that Task Force MacLean/Faith had held off for five days a significantly larger force than previously thought and that their stand was a significant factor in the Marines' survival. This was eventually recognized in September 1999 when, for its actions at Chosin, Task Force Faith was awarded the Presidential Unit Citation, an award that General Smith blocked when it was first proposed in 1952.

The Marines evacuated from North Korea and spent January and most of February 1951 rebuilding in the relatively secure South Korea, where they destroyed the well-respected but already weakened North Korean 10th Division in counter-guerrilla operations during the Second Battle of Wonju. The Marines returned to regular and heavy action on 21 February in Operation Killer.

Wider effect on the war
The battle ended the UN force's expectation of total victory, including the capture of North Korea and the reunification of the peninsula. By the end of 1950, PVA/KPA forces had recaptured North Korea and pushed UN forces back south of the 38th parallel. Serious consideration was given to the evacuation of all US forces from the Korean peninsula and US military leaders made secret contingency plans to do so. The disregard by Far Eastern Command under MacArthur of the initial warnings and diplomatic hints by the PVA almost led the entire UN army to disaster at Ch'ongch'on River and Chosin Reservoir and only after the formation and stabilization of a coherent UN defensive line under Lieutenant General Matthew Ridgway did the "period of headlong retreats from an attacking, unsuspected foe" cease.

On the other hand, the battle affected the PVA in two ways, both of which had the result of helping the UN Command to secure its position in South Korea, while losing North Korea. First, according to historian Shu Guang Zhang, PVA commanders were persuaded by their victories at Chosin and Ch'ongch'on that they could "defeat American armed forces", and this led to "unrealistic expectations that the CPV [PVA] would work miracles." Second, the heavy casualties caused by sub-zero temperatures and combat, plus poor logistical support weakened the PVA's eight elite divisions of the 20th and 27th Corps. Of those eight divisions, two were forced to disband. With the absence of 12 out of 30 of Chinese divisions in Korea in early 1951, Roe says that the heavy Chinese losses at Chosin enabled the UN forces to maintain a foothold in Korea.

Request for nuclear weapons
By the end of the withdrawal, the Chinese troops had advanced and retaken almost all of North Korean territories. On 24 December 1950, MacArthur submitted a list of "retardation targets" in Korea, Manchuria and other parts of China, and requested 34 atomic bombs from Washington with the purpose of sowing a belt of radioactive cobalt to prevent further Chinese advances. His request was firmly declined and led to his later dismissal.

Legacy
The Battle of Chosin Reservoir is regarded by some historians as the most brutal in American history due to violence, casualty rate, weather conditions, and endurance. Over the course of fourteen days, 17 Medals of Honor (Army and Navy) and 78 Service Cross Medals (Army and Navy) were awarded by the United States, the second most as of 2020 after the Battle of the Bulge (20 MOHs and 83 SCMs).

American veterans of the battle are colloquially referred to as the "Chosin Few" and symbolized by the "Star of Koto-ri".

Namesakes and memorials

 * Unknown year, a street in Bayonne, NJ was named Chosin Few Way.
 * Unknown year, "Chosin" nickname and "Against All Odds" motto, 32nd Infantry Regiment
 * Unknown year, Battle of Chosin Reservoir Memorial, Veterans Memorial Park (Lawrence, Indiana)
 * Unknown year, Chosin Reservoir Campaign Memorial (Ogden, Utah)
 * 1989, Chosin Few Memorial, Forest Park (St. Louis, Missouri)
 * 1991, USS Chosin
 * 1999, "The March Out of the Chosin", Oak Ridge Cemetery (Springfield, Illinois)
 * 2010, Chosin Few Memorial, Marine Corps Base Camp Pendleton (Oceanside, California)
 * 2017, The Chosin Few Monument, Semper Fidelis Memorial Park, National Museum of the Marine Corps (Triangle, Virginia)
 * 2017, Chosin Few Memorial Highway, 40-mile portion of Route 35 (Monmouth County, New Jersey)

Films and documentaries

 * With the Marines: Chosin to Hungnam - US Navy MN-7314 (1951)
 * This Is Korea (1951)
 * Retreat, Hell! (1952)
 * Hold Back the Night (1956)
 * Ode to My Father (국제시장) (2014)
 * Against the Odds, Bloody George at the Chosin Reservoir (2015)
 * Year Hare Affair, Season 1 Episode 3 (那年那兔那些事儿) (2015)
 * American Experience: The Battle of Chosin (2016)
 * The Battle at Lake Changjin (2021)
 * The Battle at Lake Changjin II (2022)
 * Devotion (2022)

title: Battle of Chosin Reservoir


text:
XY sex-determination system

The XY sex-determination system is a sex-determination system used to classify many mammals, including humans, some insects (Drosophila), some snakes, some fish (guppies), and some plants (Ginkgo tree). In this system, the sex of an individual is determined by a pair of sex chromosomes. Females have two of the same kind of sex chromosome (XX), and are called the homogametic sex. Males have two different kinds of sex chromosomes (XY), and are called the heterogametic sex.

In humans, the presence of the Y chromosome is responsible for triggering male development; in the absence of the Y chromosome, the fetus will undergo female development. There are various exceptions, such as individuals with Klinefelter syndrome (who have XXY chromosomes), Swyer syndrome (females with XY chromosomes), and XX male syndrome (de la Chapelle syndrome, males with XX chromosomes), however these exceptions are rare. In some instances, a seemingly normal female with a vagina, cervix, and ovaries has XY chromosomes, but the SRY gene has been shut down. In most species with XY sex determination, an organism must have at least one X chromosome in order to survive.

The XY system contrasts in several ways with the ZW sex-determination system found in birds, some insects, many reptiles, and various other animals, in which the heterogametic sex is female. It had been thought for several decades that in all snakes sex was determined by the ZW system, but there had been observations of unexpected effects in the genetics of species in the families Boidae and Pythonidae; for example, parthenogenic reproduction produced only females rather than males, which is the opposite of what is to be expected in the ZW system. In the early years of the 21st century such observations prompted research that demonstrated that all pythons and boas so far investigated definitely have the XY system of sex determination.

A temperature-dependent sex determination system is found in some reptiles and fish.

Mechanisms
All animals have a set of DNA coding for genes present on chromosomes. In humans, most mammals, and some other species, two of the chromosomes, called the X chromosome and Y chromosome, code for sex. In these species, one or more genes are present on their Y chromosome that determine maleness. In this process, an X chromosome and a Y chromosome act to determine the sex of offspring, often due to genes located on the Y chromosome that code for maleness. Offspring have two sex chromosomes: an offspring with two X chromosomes (XX) will develop female characteristics, and an offspring with an X and a Y chromosome (XY) will develop male characteristics.

Mammals
In most mammals, sex is determined by presence of the Y chromosome. This makes individuals with XXY and XYY karyotypes males, and individuals with X and XXX karyotypes females.

In the 1930s, Alfred Jost determined that the presence of testosterone was required for Wolffian duct development in the male rabbit.

SRY is a sex-determining gene on the Y chromosome in the therians (placental mammals and marsupials). Non-human mammals use several genes on the Y chromosome.

Not all male-specific genes are located on the Y chromosome. The platypus, a monotreme, use five pairs of different XY chromosomes with six groups of male-linked genes, AMH being the master switch.

Humans
A single gene (SRY) present on the Y chromosome acts as a signal to set the developmental pathway towards maleness. Presence of this gene starts off the process of virilization. This and other factors result in the sex differences in humans. The cells in females, with two X chromosomes, undergo X-inactivation, in which one of the two X chromosomes is inactivated. The inactivated X chromosome remains within a cell as a Barr body.

Other animals
Some species of turtles have convergently evolved XY sex determination systems, specifically those in Chelidae and Staurotypinae.

Other species (including most Drosophila species) use the presence of two X chromosomes to determine femaleness: one X chromosome gives putative maleness, but the presence of Y chromosome genes is required for normal male development. In the fruit fly individuals with XY are male and individuals with XX are female; however, individuals with XXY or XXX can also be female, and individuals with X can be males.

Plants
Very few dioecious angiosperm species have XY sex determination, such as the Silene latifolia. In these species sex determination is similar to mammals where male is XY and female is XX.

Other systems
Whilst XY sex determination is the most familiar, since it is the system that humans use, there are a range of alternative systems found in nature. The inverse of the XY system (called ZW to distinguish it) is used in birds and many insects, in which it is the females that are heterogametic (ZW), while males are homogametic (ZZ).

Many insects of the order Hymenoptera instead have a haplo-diploid system, where the females are full diploids (with all chromosomes appearing in pairs) but males are haploid (having just one copy of all chromosomes). Some other insects have the X0 sex-determination system, where just the sex-determining chromosome varies in ploidy (XX in females but X in males), while all other chromosomes appear in pairs in both sexes.

Genetic
In an interview for the Rediscovering Biology website, researcher Eric Vilain described how the paradigm changed since the discovery of the SRY gene: "For a long time we thought that SRY would activate a cascade of male genes. It turns out that the sex determination pathway is probably more complicated and SRY may in fact inhibit some anti-male genes.

The idea is instead of having a simplistic mechanism by which you have pro-male genes going all the way to make a male, in fact there is a solid balance between pro-male genes and anti-male genes and if there is a little too much of anti-male genes, there may be a female born and if there is a little too much of pro-male genes then there will be a male born.

We [are] entering this new era in molecular biology of sex determination where it's a more subtle dosage of genes, some pro-males, some pro-females, some anti-males, some anti-females that all interplay with each other rather than a simple linear pathway of genes going one after the other, which makes it very fascinating but very complicated to study."

In an interview by Scientific American in 2007, Vilian was asked: "It sounds as if you are describing a shift from the prevailing view that female development is a default molecular pathway to active pro-male and antimale pathways. Are there also pro-female and antifemale pathways?" He replied:

"Modern sex determination started at the end of the 1940s—1947—when the French physiologist Alfred Jost said it's the testis that is determining sex. Having a testis determines maleness, not having a testis determines femaleness. The ovary is not sex-determining. It will not influence the development of the external genitalia. Now in 1959 when the karyotype of Klinefelter [a male who is XXY] and Turner [a female who has one X] syndromes was discovered, it became clear that in humans it was the presence or the absence of the Y chromosome that's sex determining. Because all Klinefelters that have a Y are male, whereas Turners, who have no Y, are females. So it's not a dosage or the number of X's, it's really the presence or absence of the Y. So if you combine those two paradigms, you end up having a molecular basis that's likely to be a factor, a gene, that's a testis-determining factor, and that's the sex-determining gene. So the field based on that is really oriented towards finding testis-determining factors. What we discovered, though, was not just pro-testis determining factors. There are a number of factors that are there, like WNT4, like DAX1, whose function is to counterbalance the male pathway."

In mammals, including humans, the SRY gene triggers the development of non-differentiated gonads into testes rather than ovaries. However, there are cases in which testes can develop in the absence of an SRY gene (see sex reversal). In these cases, the SOX9 gene, involved in the development of testes, can induce their development without the aid of SRY. In the absence of SRY and SOX9, no testes can develop and the path is clear for the development of ovaries. Even so, the absence of the SRY gene or the silencing of the SOX9 gene are not enough to trigger sexual differentiation of a fetus in the female direction. A recent finding suggests that ovary development and maintenance is an active process, regulated by the expression of a "pro-female" gene, FOXL2. In an interview for the TimesOnline edition, study co-author Robin Lovell-Badge explained the significance of the discovery: "We take it for granted that we maintain the sex we are born with, including whether we have testes or ovaries. But this work shows that the activity of a single gene, FOXL2, is all that prevents adult ovary cells turning into cells found in testes."

Implications
Looking into the genetic determinants of human sex can have wide-ranging consequences. Scientists have been studying different sex determination systems in fruit flies and animal models to attempt an understanding of how the genetics of sexual differentiation can influence biological processes like reproduction, ageing and disease.

Maternal
In humans and many other species of animals, the father determines the sex of the child. In the XY sex-determination system, the female-provided ovum contributes an X chromosome and the male-provided sperm contributes either an X chromosome or a Y chromosome, resulting in female (XX) or male (XY) offspring, respectively.

Hormone levels in the male parent affect the sex ratio of sperm in humans. Maternal influences also impact which sperm are more likely to achieve conception.

Human ova, like those of other mammals, are covered with a thick translucent layer called the zona pellucida, which the sperm must penetrate to fertilize the egg. Once viewed simply as an impediment to fertilization, recent research indicates the zona pellucida may instead function as a sophisticated biological security system that chemically controls the entry of the sperm into the egg and protects the fertilized egg from additional sperm.

Recent research indicates that human ova may produce a chemical which appears to attract sperm and influence their swimming motion. However, not all sperm are positively impacted; some appear to remain uninfluenced and some actually move away from the egg.

Maternal influences may also be possible that affect sex determination in such a way as to produce fraternal twins equally weighted between one male and one female.

The time at which insemination occurs during the estrus cycle has been found to affect the sex ratio of the offspring of humans, cattle, hamsters, and other mammals. Hormonal and pH conditions within the female reproductive tract vary with time, and this affects the sex ratio of the sperm that reach the egg.

Sex-specific mortality of embryos also occurs.

Ancient ideas on sex determination
Aristotle believed incorrectly that the sex of an infant is determined by how much heat a man's sperm had during insemination. He wrote: "... the semen of the male differs from the corresponding secretion of the female in that it contains a principle within itself of such a kind as to set up movements also in the embryo and to concoct thoroughly the ultimate nourishment, whereas the secretion of the female contains material alone. If, then, the male element prevails it draws the female element into itself, but if it is prevailed over it changes into the opposite or is destroyed." Aristotle claimed in error that the male principle was the driver behind sex determination, such that if the male principle was insufficiently expressed during reproduction, the fetus would develop as a female.

20th century genetics
Nettie Stevens (working with beetles) and Edmund Beecher Wilson (working with hemiptera) are credited with independently discovering, in 1905, the chromosomal XY sex-determination system in insects: the fact that males have XY sex chromosomes and females have XX sex chromosomes. In the early 1920s, Theophilus Painter demonstrated that sex in humans (and other mammals) was also determined by the X and Y chromosomes, and the chromosomes that make this determination are carried by the spermatozoa.

The first clues to the existence of a factor that determines the development of testis in mammals came from experiments carried out by Alfred Jost, who castrated embryonic rabbits in utero and noticed that they all acquired a female phenotype.

In 1959, C. E. Ford and his team, in the wake of Jost's experiments, discovered that the Y chromosome was needed for a fetus to develop as male when they examined patients with Turner's syndrome, who grew up as phenotypic females, and found them to be X0 (hemizygous for X and no Y). At the same time, Jacob & Strong described a case of a patient with Klinefelter syndrome (XXY), which implicated the presence of a Y chromosome in development of maleness.

All these observations led to a consensus that a dominant gene that determines testis development (TDF) must exist on the human Y chromosome. The search for this testis-determining factor (TDF) led a team of scientists in 1990 to discover a region of the Y chromosome that is necessary for the male sex determination, which was named SRY (sex-determining region of the Y chromosome).

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

title: XY sex-determination system


text:
Window

A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent material, a sash set in a frame in the opening; the sash and frame are also referred to as a window. Many glazed windows may be opened, to allow ventilation, or closed, to exclude inclement weather. Windows may have a latch or similar mechanism to lock the window shut or to hold it open by various amounts.

Types include the eyebrow window, fixed windows, hexagonal windows, single-hung, and double-hung sash windows, horizontal sliding sash windows, casement windows, awning windows, hopper windows, tilt, and slide windows (often door-sized), tilt and turn windows, transom windows, sidelight windows, jalousie or louvered windows, clerestory windows, lancet windows, skylights, roof windows, roof lanterns, bay windows, oriel windows, thermal, or Diocletian, windows, picture windows, rose windows, emergency exit windows, stained glass windows, French windows, panel windows, double/triple-paned windows, and witch windows.

Etymology
The English language-word window originates from the Old Norse vindauga, from vindr 'wind' and auga 'eye'. In Norwegian, Nynorsk, and Icelandic, the Old Norse form has survived to this day (in Icelandic only as a less used word for a type of small open "window", not strictly a synonym for gluggi, the Icelandic word for 'window' ). In Swedish, the word vindöga remains as a term for a hole through the roof of a hut, and in the Danish language vindue and Norwegian Bokmål vindu, the direct link to eye is lost, just as for window. The Danish (but not the Bokmål) word is pronounced fairly similarly to window.

Window is first recorded in the early 13th century, and originally referred to an unglazed hole in a roof. Window replaced the Old English eagþyrl, which literally means 'eye-hole', and eagduru 'eye-door'. Many Germanic languages, however, adopted the Latin word fenestra to describe a window with glass, such as standard Swedish fönster, or German Fenster. The use of window in English is probably because of the Scandinavian influence on the English language by means of loanwords during the Viking Age. In English, the word fenester was used as a parallel until the mid-18th century. Fenestration is still used to describe the arrangement of windows within a façade, as well as defenestration, meaning 'to throw out of a window'.

History
The Romans were the first known to use glass for windows, a technology likely first produced in Roman Egypt, in Alexandria c. 100 AD. Presentations of windows can be seen in ancient Egyptian wall art and sculptures from Assyria. Paper windows were economical and widely used in ancient China, Korea, and Japan. In England, glass became common in the windows of ordinary homes only in the early 17th century whereas windows made up of panes of flattened animal horn were used as early as the 14th century. In the 19th century American west, greased paper windows came to be used by pioneering settlers. Modern-style floor-to-ceiling windows became possible only after the industrial plate glass making processes were fully perfected.

Technologies
In the 13th century BC, the earliest windows were unglazed openings in a roof to admit light during the day. Later, windows were covered with animal hide, cloth, or wood. Shutters that could be opened and closed came next. Over time, windows were built that both protected the inhabitants from the elements and transmitted light, using multiple small pieces of translucent material, such as flattened pieces of translucent animal horn, paper sheets, thin slices of marble (such as fengite), or pieces of glass, set in frameworks of wood, iron or lead. In the Far East, paper was used to fill windows. The Romans were the first known users of glass for windows, exploiting a technology likely first developed in Roman Egypt. Specifically, in Alexandria c. 100 CE, cast-glass windows, albeit with poor optical properties, began to appear, but these were small thick productions, little more than blown-glass jars (cylindrical shapes) flattened out into sheets with circular striation patterns throughout. It would be over a millennium before window glass became transparent enough to see through clearly, as we expect now. In 1154, Al-Idrisi described glass windows as a feature of the palace belonging to the king of the Ghana Empire.

Over the centuries techniques were developed to shear through one side of a blown glass cylinder and produce thinner rectangular window panes from the same amount of glass material. This gave rise to tall narrow windows, usually separated by a vertical support called a mullion. Mullioned glass windows were the windows of choice among the European well-to-do, whereas paper windows were economical and widely used in ancient China, Korea, and Japan. In England, glass became common in the windows of ordinary homes only in the early-17th century, whereas windows made up of panes of flattened animal horn were used as early as the 14th century.

Modern-style floor-to-ceiling windows became possible only after the industrial plate glass-making processes were perfected. Modern windows are usually filled using glass, although transparent plastic is also used.

Fashions and trends
The introduction of lancet windows into Western European church architecture from the 12th century CE built on a tradition of arched windows inserted between columns, and led not only to tracery and elaborate stained-glass windows but also to a long-standing motif of pointed or rounded window-shapes in ecclesiastical buildings, still seen in many churches today.

Peter Smith discusses overall trends in early-modern rural Welsh window architecture: Up to about 1680 windows tended to be horizontal in proportion, a shape suitable for lighting the low-ceilinged rooms that had resulted from the insertion of the upper floor into the hall-house. After that date vertically proportioned windows came into fashion, partly at least as a response to the Renaissance taste for the high ceiling. Since 1914 the wheel has come full circle and a horizontally proportioned window is again favoured.

The spread of plate-glass technology made possible the introduction of picture windows (in Levittown, Pennsylvania, founded 1951–1952).

Many modern day windows may have a window screen or mesh, often made of aluminum or fibreglass, to keep bugs out when the window is opened. Windows are primarily designed to facilitate a vital connection with the outdoors, offering those within the confines of the building visual access to the everchanging events occurring outside. The provision of this connection serves as an integral safeguard for the health and well-being of those inhabiting buildings, lest they experience the detrimental effects of enclosed buildings devoid of windows. Among the myriad criteria for the design of windows, several pivotal criteria have emerged in daylight standards: location, time, weather, nature, and people. Of these criteria, windows that are designed to provide views of nature are considered to be the most important by people.

Cross
A cross-window is a rectangular window usually divided into four lights by a mullion and transom that form a Latin cross.

Eyebrow
The term eyebrow window is used in two ways: a curved top window in a wall or an eyebrow dormer; and a row of small windows usually under the front eaves such as the James-Lorah House in Pennsylvania.

Fixed
A fixed window is a window that cannot be opened, whose function is limited to allowing light to enter (unlike an unfixed window, which can open and close). Clerestory windows in church architecture are often fixed. Transom windows may be fixed or operable. This type of window is used in situations where light or vision alone is needed as no ventilation is possible in such windows without the use of trickle vents or overglass vents.

Single-hung sash
A single-hung sash window is a window that has one sash that is movable (usually the bottom one) and the other fixed. This is the earlier form of sliding sash window and is also cheaper.

Double-hung sash
A sash window is the traditional style of window in the United Kingdom, and many other places that were formerly colonized by the UK, with two parts (sashes) that overlap slightly and slide up and down inside the frame. The two parts are not necessarily the same size; where the upper sash is smaller (shorter) it is termed a cottage window. Currently, most new double-hung sash windows use spring balances to support the sashes, but traditionally, counterweights held in boxes on either side of the window were used. These were and are attached to the sashes using pulleys of either braided cord or, later, purpose-made chain. Three types of spring balances are called a tape or clock spring balance; channel or block-and-tackle balance, and a spiral or tube balance.

Double-hung sash windows were traditionally often fitted with shutters. Sash windows can be fitted with simplex hinges that let the window be locked into hinges on one side, while the rope on the other side is detached—so the window can be opened for fire escape or cleaning.

Foldup

A foldup has two equal sashes similar to a standard double-hung but folds upward allowing air to pass through nearly the full-frame opening. The window is balanced using either springs or counterbalances, similar to a double-hung. The sashes can be either offset to simulate a double-hung, or in-line. The inline versions can be made to fold inward or outward. The inward swinging foldup windows can have fixed screens, while the outward swinging ones require movable screens. The windows are typically used for screen rooms, kitchen pass-throughs, or egress.

Horizontal sliding sash
A horizontal sliding sash window has two or more sashes that overlap slightly but slide horizontally within the frame. In the UK, these are sometimes called Yorkshire sash windows, presumably because of their traditional use in that county.

Casement

A casement window is a window with a hinged sash that swings in or out like a door comprising either a side-hung, top-hung (also called "awning window"; see below), or occasionally bottom-hung sash or a combination of these types, sometimes with fixed panels on one or more sides of the sash. In the US, these are usually opened using a crank, but in parts of Europe, they tend to use projection friction stays and espagnolette locking. Formerly, plain hinges were used with a casement stay. Handing applies to casement windows to determine direction of swing; a casement window may be left-handed, right-handed, or double. The casement window is the dominant type now found in modern buildings in the UK and many other parts of Europe.

Awning

An awning window is a casement window that is hung horizontally, hinged on top, so that it swings outward like an awning. In addition to being used independently, they can be stacked, several in one opening, or combined with fixed glass. They are particularly useful for ventilation.

Hopper
A hopper window is a bottom-pivoting casement window that opens by tilting vertically, typically to the inside, resembling a hopper chute.

Pivot
A pivot window is a window hung on one hinge on each of two opposite sides which allows the window to revolve when opened. The hinges may be mounted top and bottom (Vertically Pivoted) or at each jamb (Horizontally Pivoted). The window will usually open initially to a restricted position for ventilation and, once released, fully reverse and lock again for safe cleaning from inside. Modern pivot hinges incorporate a friction device to hold the window open against its weight and may have restriction and reversed locking built-in. In the UK, where this type of window is most common, they were extensively installed in high-rise social housing.

Tilt and slide
A tilt and slide window is a window (more usually a door-sized window) where the sash tilts inwards at the top similar to a hopper window and then slides horizontally behind the fixed pane.

Tilt and turn
A tilt and turn window can both tilt inwards at the top or open inwards from hinges at the side. This is the most common type of window in Germany, its country of origin. It is also widespread in many other European countries. In Europe, it is usual for these to be of the "turn first" type. i.e. when the handle is turned to 90 degrees the window opens in the side hung mode. With the handle turned to 180 degrees the window opens in bottom hung mode. Most usually in the UK the windows will be "tilt first" i.e. bottom hung at 90 degrees for ventilation and side hung at 180 degrees for cleaning the outer face of the glass from inside the building.

Transom
A transom window is a window above a door. In an exterior door the transom window is often fixed, in an interior door, it can open either by hinges at top or bottom, or rotate on hinges. It provided ventilation before forced air heating and cooling. A fan-shaped transom is known as a fanlight, especially in the British Isles.

Side light
Windows beside a door or window are called side-, wing-, margen-lights, and flanking windows.

Jalousie window

Also known as a louvered window, the jalousie window consists of parallel slats of glass or acrylic that open and close like a Venetian blind, usually using a crank or a lever. They are used extensively in tropical architecture. A jalousie door is a door with a jalousie window.

Clerestory

A clerestory window is a window set in a roof structure or high in a wall, used for daylighting.

Skylight

A skylight is a window built into a roof structure. This type of window allows for natural daylight and moonlight.

Roof

A roof window is a sloped window used for daylighting, built into a roof structure. It is one of the few windows that could be used as an exit. Larger roof windows meet building codes for emergency evacuation.

Roof lantern
A roof lantern is a multi-paned glass structure, resembling a small building, built on a roof for day or moon light. Sometimes includes an additional clerestory. May also be called a cupola.

Bay

A bay window is a multi-panel window, with at least three panels set at different angles to create a protrusion from the wall line.

Oriel
An oriel window is a form of bay window. This form most often appears in Tudor-style houses and monasteries. It projects from the wall and does not extend to the ground. Originally a form of porch, they are often supported by brackets or corbels.

Thermal
Thermal, or Diocletian, windows are large semicircular windows (or niches) which are usually divided into three lights (window compartments) by two mullions. The central compartment is often wider than the two side lights on either side of it.

Picture
A picture window is a large fixed window in a wall, typically without glazing bars, or glazed with only perfunctory glazing bars (muntins) near the edge of the window. Picture windows provide an unimpeded view, as if framing a picture.

Multi-lite
A multi-lite window is a window glazed with small panes of glass separated by wooden or lead glazing bars, or muntins, arranged in a decorative glazing pattern often dictated by the building's architectural style. Due to the historic unavailability of large panes of glass, the multi-lit (or lattice window) was the most common window style until the beginning of the 20th century, and is still used in traditional architecture.

Emergency exit/egress
An emergency exit window is a window big enough and low enough so that occupants can escape through the opening in an emergency, such as a fire. In many countries, exact specifications for emergency windows in bedrooms are given in many building codes. Specifications for such windows may also allow for the entrance of emergency rescuers. Vehicles, such as buses, aircraft, and trains frequently have emergency exit windows as well.

Stained glass
A stained glass window is a window composed of pieces of colored glass, transparent, translucent or opaque, frequently portraying persons or scenes. Typically the glass in these windows is separated by lead glazing bars. Stained glass windows were popular in Victorian houses and some Wrightian houses, and are especially common in churches.

French
A French door has two rows of upright rectangular glass panes (lights) extending its full length; and two of these doors on an exterior wall and without a mullion separating them, that open outward with opposing hinges to a terrace or porch, are referred to as a French window. Sometimes these are set in pairs or multiples thereof along the exterior wall of a very large room, but often, one French window is placed centrally in a typically sized room, perhaps among other fixed windows flanking the feature. French windows are known as porte-fenêtre in France and portafinestra in Italy, and frequently are used in modern houses.

Double-paned

Double-paned windows have two parallel panes (slabs of glass) with a separation of typically about 1 cm; this space is permanently sealed and filled at the time of manufacture with dry air or other dry nonreactive gas. Such windows provide a marked improvement in thermal insulation (and usually in acoustic insulation as well) and are resistant to fogging and frosting caused by temperature differential. They are widely used for residential and commercial construction in intemperate climates. In the UK, double-paned and triple-paned are referred to as double-glazing and triple-glazing. Triple-paned windows are now a common type of glazing in central to northern Europe. Quadruple glazing is now being introduced in Scandinavia.

Hexagonal window

A hexagonal window is a hexagon-shaped window, resembling a bee cell or crystal lattice of graphite. The window can be vertically or horizontally oriented, openable or dead. It can also be regular or elongately-shaped and can have a separator (mullion). Typically, the cellular window is used for an attic or as a decorative feature, but it can also be a major architectural element to provide the natural lighting inside buildings.

Guillotine window
A guillotine window is a window that opens vertically. Guillotine windows have more than one sliding frame, and open from bottom to top or top to bottom.

Terms
EN 12519 is the European standard that describes windows terms officially used in EU Member States. The main terms are:

EN 12519 is the European standard that describes windows terms officially used in EU Member States. The main terms are:
 * Light, or Lite, is the area between the outer parts of a window (transom, sill and jambs), usually filled with a glass pane. Multiple panes are divided by mullions when load-bearing, muntins when not.
 * Lattice light is a compound window pane madeup of small pieces of glass held together in a lattice.
 * Fixed window is a unit of one non-moving lite. The terms single-light, double-light, etc., refer to the number of these glass panes in a window.
 * Sash unit is a window consisting of at least one sliding glass component, typically composed of two lites (known as a double-light).
 * Replacement window in the United States means a framed window designed to slip inside the original window frame from the inside after the old sashes are removed. In Europe, it usually means a complete window including a replacement outer frame.
 * New construction window, in the US, means a window with a nailing fin that is inserted into a rough opening from the outside before applying siding and inside trim. A nailing fin is a projection on the outer frame of the window in the same plane as the glazing, which overlaps the prepared opening, and can thus be 'nailed' into place. In the UK and mainland Europe, windows in new-build houses are usually fixed with long screws into expanding plastic plugs in the brickwork. A gap of up to 13 mm is left around all four sides, and filled with expanding polyurethane foam. This makes the window fixing weatherproof but allows for expansion due to heat.
 * Lintel is a beam over the top of a window, also known as a transom.
 * Window sill is the bottom piece in a window frame. Window sills slant outward to drain water away from the inside of the building.
 * Secondary glazing is an additional frame applied to the inside of an existing frame, usually used on protected or listed buildings to achieve higher levels of thermal and sound insulation without compromising the look of the building
 * Decorative millwork is the moulding, cornices and lintels often decorating the surrounding edges of the window.

Labeling
The United States NFRC Window Label lists the following terms:
 * Thermal transmittance (U-factor), best values are around U-0.15 (equal to 0.8 W/m2/K)
 * Solar heat gain coefficient (SHGC), ratio of solar heat (infrared) passing through the glass to incident solar heat
 * Visible transmittance (VT), ratio of transmitted visible light divided by incident visible light
 * Air leakage (AL), measured in cubic foot per minute per linear foot of crack between sash and frame
 * Condensation resistance (CR), measured between 1 and 100 (the higher the number, the higher the resistance of the formation of condensation)

The European harmonised standard hEN 14351–1, which deals with doors and windows, defines 23 characteristics (divided into essential and non essential). Two other, preliminary European Norms that are under development deal with internal pedestrian doors (prEN 14351–2), smoke and fire resisting doors, and openable windows (prEN 16034).

Construction

Windows can be a significant source of heat transfer. Therefore, insulated glazing units consist of two or more panes to reduce the transfer of heat.

Grids or muntins
These are the pieces of framing that separate a larger window into smaller panes. In older windows, large panes of glass were quite expensive, so muntins let smaller panes fill a larger space. In modern windows, light-colored muntins still provide a useful function by reflecting some of the light going through the window, making the window itself a source of diffuse light (instead of just the surfaces and objects illuminated within the room). By increasing the indirect illumination of surfaces near the window, muntins tend to brighten the area immediately around a window and reduce the contrast of shadows within the room.

Frame and sash construction
Frames and sashes can be made of the following materials: Composites (also known as Hybrid Windows) are start since early 1998 and combine materials like aluminium + pvc or wood to obtain aesthetics of one material with the functional benefits of another. A special class of PVC window frames, uPVC window frames, became widespread since the late 20th century, particularly in Europe: there were 83.5 million installed by 1998 with numbers still growing as of 2012.

Glazing and filling
Low-emissivity coated panes reduce heat transfer by radiation, which, depending on which surface is coated, helps prevent heat loss (in cold climates) or heat gains (in warm climates).

High thermal resistance can be obtained by evacuating or filling the insulated glazing units with gases such as argon or krypton, which reduces conductive heat transfer due to their low thermal conductivity. Performance of such units depends on good window seals and meticulous frame construction to prevent entry of air and loss of efficiency.

Modern double-pane and triple-pane windows often include one or more low-e coatings to reduce the window's U-factor (its insulation value, specifically its rate of heat loss). In general, soft-coat low-e coatings tend to result in a lower solar heat gain coefficient (SHGC) than hard-coat low-e coatings.

Modern windows are usually glazed with one large sheet of glass per sash, while windows in the past were glazed with multiple panes separated by glazing bars, or muntins, due to the unavailability of large sheets of glass. Today, glazing bars tend to be decorative, separating windows into small panes of glass even though larger panes of glass are available, generally in a pattern dictated by the architectural style at use. Glazing bars are typically wooden, but occasionally lead glazing bars soldered in place are used for more intricate glazing patterns.

Other construction details
Many windows have movable window coverings such as blinds or curtains to keep out light, provide additional insulation, or ensure privacy. Windows allow natural light to enter, but too much can have negative effects such as glare and heat gain. Additionally, while windows let the user see outside, there must be a way to maintain privacy on in the inside. Window coverings are practical accommodations for these issues.

Sun incidence angle
Historically, windows are designed with surfaces parallel to vertical building walls. Such a design allows considerable solar light and heat penetration due to the most commonly occurring incidence of sun angles. In passive solar building design, an extended eave is typically used to control the amount of solar light and heat entering the window(s).

An alternative method is to calculate an optimum window mounting angle that accounts for summer sun load minimization, with consideration of actual latitude of the building. This process has been implemented, for example, in the Dakin Building in Brisbane, California—in which most of the fenestration is designed to reflect summer heat load and help prevent summer interior over-illumination and glare, by canting windows to nearly a 45 degree angle.

Solar window
Photovoltaic windows not only provide a clear view and illuminate rooms, but also convert sunlight to electricity for the building. In most cases, translucent photovoltaic cells are used.

Passive solar
Passive solar windows allow light and solar energy into a building while minimizing air leakage and heat loss. Properly positioning these windows in relation to sun, wind, and landscape—while properly shading them to limit excess heat gain in summer and shoulder seasons, and providing thermal mass to absorb energy during the day and release it when temperatures cool at night—increases comfort and energy efficiency. Properly designed in climates with adequate solar gain, these can even be a building's primary heating system.

Coverings
A window covering is a shade or screen that provides multiple functions. Some coverings, such as drapes and blinds provide occupants with privacy. Some window coverings control solar heat gain and glare. There are external shading devices and internal shading devices. Low-e window film is a low-cost alternative to window replacement to transform existing poorly-insulating windows into energy-efficient windows. For high-rise buildings, smart glass can provide an alternative.

title: Window


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Hall

In architecture, a hall is a relatively large space enclosed by a roof and walls. In the Iron Age and early Middle Ages in northern Europe, a mead hall was where a lord and his retainers ate and also slept. Later in the Middle Ages, the great hall was the largest room in castles and large houses, and where the servants usually slept. As more complex house plans developed, the hall remained a large room for dancing and large feasts, often still with servants sleeping there. It was usually immediately inside the main door. In modern British houses, an entrance hall next to the front door remains an indispensable feature, even if it is essentially merely a corridor.

Today, the (entrance) hall of a house is the space next to the front door or vestibule leading to the rooms directly and/or indirectly. Where the hall inside the front door of a house is elongated, it may be called a passage, corridor (from Spanish corredor used in El Escorial and 100 years later in Castle Howard), or hallway.

History
In warmer climates, the houses of the wealthy were often built around a courtyard, but in northern areas manors were built around a great hall. The hall was home to the hearth and was where all the residents of the house would eat, work, and sleep. One common example of this form is the longhouse. Only particularly messy tasks would be done in separate rooms on the periphery of the hall. Still today the term hall is often used to designate a country house such as a hall house, or specifically a Wealden hall house, and manor houses.

In later medieval Europe, the main room of a castle or manor house was the great hall. In a medieval building, the hall was where the fire was kept. As heating technology improved and a desire for privacy grew, tasks moved from the hall to other rooms. First, the master of the house withdrew to private bedrooms and eating areas. Over time servants and children also moved to their own areas, while work projects were also given their own chambers leaving the hall for special functions. With time, its functions as dormitory, kitchen, parlour, and so on were divided into separate rooms or, in the case of the kitchen, a separate building.

Until the early modern era that majority of the population lived in houses with a single room. In the 17th century, even lower classes began to have a second room, with the main chamber being the hall and the secondary room the parlor. The hall and parlor house was found in England and was a fundamental, historical floor plan in parts of the United States from 1620 to 1860.

In Europe, as the wealthy embraced multiple rooms initially the common form was the enfilade, with rooms directly connecting to each other. In 1597 John Thorpe is the first recorded architect to replace multiple connected rooms with rooms along a corridor each accessed by a separate door.

Collegiate halls
Many institutions and buildings at colleges and universities are formally titled "_______ Hall", typically being named after the person who endowed it, for example, King's Hall, Cambridge. Others, such as Lady Margaret Hall, Oxford, commemorate respected people. Between these in age, Nassau Hall at Princeton University began as the single building of the then college. In medieval origin, these were the halls in which the members of the university lived together during term time. In many cases, some aspect of this community remains.

Some of these institutions are titled "Hall" instead of "College" because at the time of their foundation they were not recognised as colleges (in some cases because their foundation predated the existence of colleges) and did not have the appropriate Royal Charter. Examples at the University of Oxford are:

 * St Edmund Hall
 * Hart Hall (now Hertford College)
 * Lady Margaret Hall
 * The (currently six) Permanent private halls.

In colleges of the universities of Oxford and Cambridge, the term "Hall" is also used for the dining hall for students, with High Table at one end for fellows. Typically, at "Formal Hall", gowns are worn for dinner during the evening, whereas for "informal Hall" they are not. The medieval collegiate dining hall, with a dais for the high table at the upper end and a screen passage at the lower end, is a modified or assimilated form of the Great hall.

Meeting hall
A hall is also a building consisting largely of a principal room, that is rented out for meetings and social affairs. It may be privately or government-owned, such as a function hall owned by one company used for weddings and cotillions (organized and run by the same company on a contractual basis) or a community hall available for rent to anyone, such as a British village hall.

Religious halls
In religious architecture, as in Islamic architecture, the prayer hall is a large room dedicated to the practice of worship. (example: the prayer hall of the Great Mosque of Kairouan in Tunisia). A hall church is a church with a nave and side aisles of approximately equal height. Many churches have an associated church hall used for meetings and other events.

Public buildings
Following a line of similar development, in office buildings and larger buildings (theatres, cinemas etc.), the entrance hall is generally known as the foyer (the French for fireplace). The atrium, a name sometimes used in public buildings for the entrance hall, was the central courtyard of a Roman house.

Types
In architecture, the term "double-loaded" describes corridors that connect to rooms on both sides. Conversely, a single-loaded corridor only has rooms on one side (and possible windows on the other). A blind corridor does not lead anywhere.

 * Billiard hall
 * City hall, town hall or village hall
 * Concert hall
 * Concourse (at a large transportation station)
 * Convention center (exhibition hall)
 * Dance hall
 * Dining hall
 * Firehall
 * Great room or great hall
 * Moot hall
 * Prayer hall, such as the sanctuary of a synagogue
 * Reading room
 * Residence hall
 * Trades hall (also called union hall, labour hall, etc.)
 * Waiting room (in large transportation stations)

title: Hall


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Closet

A closet (especially in North American English usage) is an enclosed space, with a door, used for storage, particularly that of clothes. Fitted closets are built into the walls of the house so that they take up no apparent space in the room. Closets are often built under stairs, thereby using awkward space that would otherwise go unused.

A piece of furniture such as a cabinet or chest of drawers serves the same purpose of storage, but is not a closet, which is an architectural feature rather than a piece of furniture. A closet always has space for hanging, where a cupboard may consist only of shelves for folded garments. Wardrobe can refer to a free-standing piece of furniture (also known as an armoire), but according to the Oxford English Dictionary, a wardrobe can also be a "large cupboard or cabinet for storing clothes or other linen", including "built-in wardrobe, fitted wardrobe, walk-in wardrobe, etc."

Other uses of the word
In Elizabethan and Middle English, closet referred to a small private room, an inner sanctum within a far larger house, used for prayer, reading, or study.

The use of "closet" for "toilet" dates back to 1662. In Indian English, this use continues. Related forms include earth closet and water closet (flush toilet). "Privy" meaning an outhouse derives from "private", making the connection with the Middle English use of "closet", above.

Types

 * Airing cupboard: A closet containing a water heater, with slatted shelves to allow air to circulate around the clothes or linen stored there.
 * Broom closet: A closet with top-to-bottom space used for storing cleaning items, like brooms, mops, vacuum cleaners, cleaning supplies, buckets, etc.
 * Coat closet: A closet located near the front door. Usually used to store coats, jackets, hoodies, sweatshirts, gloves, hats, scarfs, sunglasses, and boots/shoes. This kind of closet sometimes has shelving. It only has a rod and some bottom space used for clothes stored in boxes or drawers. Some may have a top shelf for storage above the rod.
 * Custom closet: A closet that is made specifically to meet the needs of the user, like a kids closet.
 * Linen-press or linen closet: A tall, narrow closet. Typically located in or near bathrooms and/or bedrooms, such a closet contains shelves used to hold items such as toiletries and linens, including towels, washcloths, or sheets.
 * Pantry: A closet or cabinet in a kitchen used for storing food, dishes, linens, and provisions. The closet may have shelves for putting food on.
 * Spear closet: A closet made to use up otherwise unused space in a building.
 * Supply closet: A closet most commonly used for storing office supplies.
 * Utility closet: A closet most commonly used for storing house appliances and cleaning supplies
 * Walk-in closet: A storage room with enough space for someone to stand in it while accessing stored items. Larger ones used for clothes shade into dressing room.
 * Wall closet: A closet in a bedroom that is built into the wall. It may be closed by curtains or folding doors, in which clothes can be stored folded on shelves.
 * Wardrobe: A small closet used for storing clothes.

Closet tax question in colonial America
Though some sources claim that colonial American houses often lacked closets because of a "closet tax" imposed by the British crown, others argue that closets were absent in most houses simply because their residents had few possessions.

Closet organizers
Closet organizers are integrated shelving systems. Different materials have advantages and disadvantages:
 * Wire shelving: Moderately difficult to install, wire shelves cannot hold much weight without giving in but are cheap.
 * Wood shelving: Difficult to install, wood shelving is sturdier and more expensive than wire.
 * Tube shelving: Easy to install, tube shelving involves few pieces and requires no cutting or measuring.

title: Closet