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A bunker is a defensive military fortification designed to protect people and valued materials from falling bombs, artillery, or other attacks. Bunkers are almost always underground, in contrast to blockhouses which are mostly above ground. [1] They were used extensively in World War I, World War II, and the Cold War for weapons facilities, command and control centers, and storage facilities. Bunkers can also be used as protection from tornadoes.
Trench bunkers are small concrete structures, partly dug into the ground. Many artillery installations, especially for coastal artillery, have historically been protected by extensive bunker systems. Typical industrial bunkers include mining sites, food storage areas, dumps for materials, data storage, and sometimes living quarters. When a house is purpose-built with a bunker, the normal location is a reinforced below-ground bathroom with fiber-reinforced plastic shells. Bunkers deflect the blast wave from nearby explosions to prevent ear and internal injuries to people sheltering in the bunker. Nuclear bunkers must also cope with the underpressure that lasts for several seconds after the shock wave passes, and block radiation.
A bunker's door must be at least as strong as the walls. In bunkers inhabited for prolonged periods, large amounts of ventilation or air conditioning must be provided. Bunkers can be destroyed with powerful explosives and bunker-busting warheads.
The word bunker originates as a Scots word for "bench, seat" recorded 1758, alongside shortened bunk "sleeping berth". [2] The word possibly has a Scandinavian origin: Old Swedish bunke means "boards used to protect the cargo of a ship". [3] In the 19th century the word came to describe a coal store in a house, or below decks in a ship. It was also used for a sand-filled depression installed on a golf course as a hazard. [4]
In the First World War the belligerents built underground shelters, called dugouts in English, while the Germans used the term Bunker. [5] [6] By the Second World War the term came to be used by the Germans to describe permanent structures both large (blockhouses), and small (pillboxes), and bombproof shelters both above ground (as in Hochbunker ) and below ground (such as the Führerbunker ). [7] The military sense of the word was imported into English during World War II, at first in reference to specifically German dug-outs; according to the Oxford English Dictionary, the sense of "military dug-out; a reinforced concrete shelter" is first recorded on 13 October 1939, in "A Nazi field gun hidden in a cemented 'bunker' on the Western front". [8] All the early references to its usage in the Oxford English Dictionary are to German fortifications. However, in the Far East the term was also applied to the earth and log positions built by the Japanese, the term appearing in a 1943 instruction manual issued by the British Indian Army and quickly gaining wide currency. [9]
By 1947 the word was familiar enough in English that Hugh Trevor-Roper in The Last Days of Hitler was describing Hitler's underground complex near the Reich Chancellery as "Hitler's own bunker" without quotes around the word bunker. [8]
This type of bunker is a small concrete structure, partly dug into the ground, which is usually a part of a trench system. Such bunkers give the defending soldiers better protection than the open trench and also include top protection against aerial attack. They also provide shelter against the weather. Some bunkers may have partially open tops to allow weapons to be discharged with the muzzle pointing upwards (e.g., mortars and anti-aircraft weapons). [10]
Many artillery installations, especially for coastal artillery, have historically been protected by extensive bunker systems. These usually housed the crews serving the weapons, protected the ammunition against counter-battery fire, and in numerous examples also protected the guns themselves, though this was usually a trade-off reducing their fields of fire. Artillery bunkers are some of the largest individual pre-Cold War bunkers. The walls of the 'Batterie Todt' gun installation in northern France were up to 3.5 metres (11 ft) thick, [11] and an underground bunker was constructed for the V-3 cannon.
Typical industrial bunkers include mining sites, food storage areas, dumps for materials, data storage, and sometimes living quarters. They were built mainly by nations like Germany during World War II to protect important industries from aerial bombardment. Industrial bunkers are also built for control rooms of dangerous activities, such as tests of rocket engines or explosive experiments. They are also built in order to perform dangerous experiments in them or to store radioactive or explosive goods. Such bunkers also exist on non-military facilities.
When a house is purpose-built with a bunker, the normal location is a reinforced below-ground bathroom with large cabinets. [12] One common design approach uses fibre-reinforced plastic shells. Compressive protection may be provided by inexpensive earth arching.[ citation needed ] The overburden is designed to shield from radiation.[ citation needed ] To prevent the shelter from floating to the surface in high groundwater, some designs have a skirt held down with the overburden. [13] It may also serve the purpose of a safe room.[ citation needed ]
Large bunkers are often bought by super rich individuals in case of political instability, and usually store or access large amounts of energy for use. They are sometimes refereed to as "luxury bunkers," and their locations are often documented. [14] [15] [16]
Munitions storage bunkers are designed to securely store explosive ordnance and contain any internal explosions. The most common configuration for high explosives storage is the igloo shaped bunker.[ citation needed ] They are often built into a hillside in order to provide additional containment mass.
A specialized version of the munitions bunker called a Gravel Gertie is designed to contain radioactive debris from an explosive accident while assembling or disassembling nuclear warheads. They are installed at all facilities in the United States and United Kingdom which do warhead assembly and disassembly, the largest being the Pantex plant in Amarillo, Texas, which has 12 Gravel Gerties. [17]
Bunkers deflect the blast wave from nearby explosions to prevent ear and internal injuries to people sheltering in the bunker. While frame buildings collapse from as little as 21 kPa (3 psi ; 0.21 bar ) of overpressure, bunkers are regularly constructed to survive over 1,000 kPa (150 psi; 10 bar). This substantially decreases the likelihood that a bomb (other than a bunker buster) can harm the structure.
The basic plan is to provide a structure that is very strong in physical compression. The most common purpose-built structure is a buried, steel reinforced concrete vault or arch. Most expedient blast shelters are civil engineering structures that contain large, buried tubes or pipes such as sewage or rapid transit tunnels. Improvised purpose-built blast shelters normally use earthen arches or vaults. To form these, a narrow, 1–2-metre (3.5–6.5 ft), flexible tent of thin wood is placed in a deep trench, and then covered with cloth or plastic, and then covered with 1–2 m (3.5–6.5 feet) of tamped earth.
A large ground shock can move the walls of a bunker several centimeters in a few milliseconds. Bunkers designed for large ground shocks must have sprung internal buildings to protect inhabitants from the walls and floors. [18]
Nuclear bunkers must also cope with the underpressure that lasts for several seconds after the shock wave passes, and block radiation. Usually, these features are easy to provide. The overburden (soil) and structure provide substantial radiation shielding, and the negative pressure is usually only 1⁄3 of the overpressure. [19]
The doors must be at least as strong as the walls. The usual design is now starting to incorporate vault doors. To reduce the weight, the door is normally constructed of steel, with a fitted steel lintel and frame. Very thick wood also serves and is more resistant to heat because it chars rather than melts.[ citation needed ] If the door is on the surface and will be exposed to the blast wave, the edge of the door is normally counter-sunk in the frame so that the blast wave or a reflection cannot lift the edge. A bunker should have two doors. Door shafts may double as ventilation shafts to reduce digging.
In bunkers inhabited for prolonged periods, large amounts of ventilation or air conditioning must be provided in order to prevent ill effects of heat. In bunkers designed for war-time use, manually operated ventilators must be provided because supplies of electricity or gas are unreliable. One of the most efficient manual ventilator designs is the Kearny Air Pump. Ventilation openings in a bunker must be protected by blast valves. A blast valve is closed by a shock wave, but otherwise remains open. One form of expedient blast valve is worn flat rubber tire treads nailed or bolted to frames strong enough to resist the maximum overpressure. [20]
Bunkers can be destroyed with powerful explosives and bunkerbusting warheads. The crew of a pillbox can be killed with flamethrowers. [21] Complex, well-built and well-protected fortifications are often vulnerable to attacks on access points. If the exits to the surface can be closed off, those manning the facility can be trapped. The fortification can then be bypassed.
Famous bunkers include the post-World War I Maginot Line on the French eastern border and Czechoslovak border fortifications mainly on the northern Czech border facing Germany (but to lesser extent all around), Fort Eben-Emael in Belgium, Alpine Wall on the north of Italy, World War II Führerbunker and in Italy, industrial Marnate's Bunker, the V-weapon installations in Germany (Mittelwerk) & France (La Coupole, and the Blockhaus d'Éperlecques) and the Cold War installations in the United States (Cheyenne Mountain Complex, Site R, and The Greenbrier), United Kingdom (Burlington), Sweden (Boden Fortress) and Canada (Diefenbunker). In Switzerland, there is an unusually large number of bunkers because of a law requiring protective shelters to be constructed for all new buildings since 1963, as well as a number of bunkers built as part of its National Redoubt military defense plan. [22] Some of Switzerland's bunkers have since become tourist attractions housing hotels and museums such as Sasso San Gottardo Museum. [23]
The Soviet Union maintained huge bunkers (one of the secondary uses of the very deeply dug Moscow Metro and Kyiv metro systems was as nuclear shelters). A number of facilities were constructed in China, such as Beijing's Underground City and Underground Project 131 in Hubei; in Albania, Enver Hoxha dotted the country with hundreds of thousands of bunkers. In the United States, the Presidential Emergency Operations Center underneath the East Wing of the White House serves as a secure shelter and communications center for the President of the United States in case of an emergency.
A fallout shelter is an enclosed space specially designated to protect occupants from radioactive debris or fallout resulting from a nuclear explosion. Many such shelters were constructed as civil defense measures during the Cold War.
A thermobaric weapon, also called an aerosol bomb, or a vacuum bomb, is a type of explosive munition that works by dispersing an aerosol cloud of gas, liquid or powdered explosive. The fuel is usually a single compound, rather than a mixture of multiple molecules. Many types of thermobaric weapons can be fitted to hand-held launchers, and can also be launched from airplanes.
A nuclear bunker buster, also known as an earth-penetrating weapon (EPW), is the nuclear equivalent of the conventional bunker buster. The non-nuclear component of the weapon is designed to penetrate soil, rock, or concrete to deliver a nuclear warhead to an underground target. These weapons would be used to destroy hardened, underground military bunkers or other below-ground facilities. An underground explosion releases a larger fraction of its energy into the ground, compared to a surface burst or air burst explosion at or above the surface, and so can destroy an underground target using a lower explosive yield. This in turn could lead to a reduced amount of radioactive fallout. However, it is unlikely that the explosion would be completely contained underground. As a result, significant amounts of rock and soil would be rendered radioactive and lofted as dust or vapor into the atmosphere, generating significant fallout.
A bunker buster is a type of munition that is designed to penetrate hardened targets or targets buried deep underground, such as military bunkers.
A fortification is a military construction designed for the defense of territories in warfare, and is used to establish rule in a region during peacetime. The term is derived from Latin fortis ("strong") and facere.
A bomb shelter is a structure designed to provide protection against the effects of a bomb.
The effects of a nuclear explosion on its immediate vicinity are typically much more destructive and multifaceted than those caused by conventional explosives. In most cases, the energy released from a nuclear weapon detonated within the lower atmosphere can be approximately divided into four basic categories:
Air raid shelters are structures for the protection of non-combatants as well as combatants against enemy attacks from the air. They are similar to bunkers in many regards, although they are not designed to defend against ground attack.
A storm shelter or storm cellar is a type of underground bunker designed to protect the occupants from violent severe weather, particularly tornadoes. They are most frequently seen in the Midwest and Southeastern United States where tornadoes are generally frequent and the low water table permits underground structures.
A blockhouse is a small fortification, usually consisting of one or more rooms with loopholes, allowing its defenders to fire in various directions. It is usually an isolated fort in the form of a single building, serving as a defensive strong point against any enemy that does not possess siege equipment or, in modern times, artillery, air force or cruise missiles. A fortification intended to resist these weapons is more likely to qualify as a fortress or a redoubt, or in modern times, be an underground bunker. However, a blockhouse may also refer to a room within a larger fortification, usually a battery or redoubt.
The Diefenbunker, formerly known by its military designation, Canadian Forces Station Carp (CFS Carp), is a large underground four-storey reinforced concrete bunker and nuclear fallout shelter located in the rural area of Carp, Ontario approximately 30 km (19 mi) west of downtown Ottawa. Between 1957 and 1961, during the Cold War the Government of Canada led by then Prime Minister John Diefenbaker authorized the Diefenbunker to be designed and built as the Central Emergency Government Headquarters (CEGHQ Carp) in an attempt to ensure the continuity of government subsequent to a nuclear weapons attack by the Soviet Union. In 1994, CFS Carp was decommissioned and closed.
The Mk/B53 was a high-yield bunker buster thermonuclear weapon developed by the United States during the Cold War. Deployed on Strategic Air Command bombers, the B53, with a yield of 9 megatons, was the most powerful weapon in the U.S. nuclear arsenal after the last B41 nuclear bombs were retired in 1976.
A blast shelter is a place where people can go to protect themselves from blasts and explosions, like those from bombs, or in hazardous worksites, such as on oil and gas refineries or petrochemical facilities. It differs from a fallout shelter, in that its main purpose is to protect from shock waves and overpressure instead of from radioactive precipitation, as a fallout shelter does. It is also possible for a shelter to protect from both blasts and fallout.
A blast valve is used to protect a shelter, such as a fallout shelter or bunker, from the effects of sudden outside air pressure changes. A nuclear weapon creates a shock wave, which may produce sudden pressure changes of more than an atmosphere even several kilometres from the detonation point. After the shock wave passes, a sudden negative pressure follows.
Tunnel warfare is using tunnels and other underground cavities in war. It often includes the construction of underground facilities in order to attack or defend, and the use of existing natural caves and artificial underground facilities for military purposes. Tunnels can be used to undermine fortifications and slip into enemy territory for a surprise attack, while it can strengthen a defense by creating the possibility of ambush, counterattack and the ability to transfer troops from one portion of the battleground to another unseen and protected. Also, tunnels can serve as shelter from enemy attack.
Dispersal is a military practice of dispersing or spreading out potentially vulnerable military assets, such as soldiers, aircraft, ships, tanks, weapons, vehicles, and similar equipment of an army, navy, or air force. Its primary objective is to minimise any potential effects of collateral damage, from incoming munitions such as artillery, bombs and missiles. Dispersal increases the number of artillery rounds needed to neutralise or destroy a military unit in proportion to the dispersal of the said unit. If a division doubles the area it takes up, it will double the number of artillery rounds needed to do the same damage to it. As more targets are spread out or dispersed, more artillery and / or bombs are required to hit all the individual targets.
The earthquake bomb, or seismic bomb, was a concept that was invented by the British aeronautical engineer Barnes Wallis early in World War II and subsequently developed and used during the war against strategic targets in Europe. A seismic bomb differs somewhat in concept from a traditional bomb, which usually explodes at or near the surface and destroys its target directly by explosive force; in contrast, a seismic bomb is dropped from high altitude to attain very high speed as it falls and upon impact, penetrates and explodes deep underground, causing massive caverns or craters known as camouflets, as well as intense shockwaves. In this way, the seismic bomb can affect targets that are too massive to be affected by a conventional bomb, as well as damage or destroy difficult targets such as bridges and viaducts.
Czechoslovakia built a system of border fortifications as well as some fortified defensive lines inland, from 1935 to 1938 as a defensive countermeasure against the rising threat of Nazi Germany. The objective of the fortifications was to prevent the taking of key areas by an enemy—not only Germany but also Hungary and Poland—by means of a sudden attack before the mobilization of the Czechoslovak Army could be completed, and to enable effective defense until allies—Britain and France, and possibly the Soviet Union—could help.
Abo Elementary School in Artesia, New Mexico, United States, was the first public school in the United States constructed entirely underground and equipped to function as an advanced fallout shelter. Designed at the height of the Cold War and completed in 1962, the school had a concrete slab roof which doubled as the school's playground. It contained a large storage facility with room for emergency rations and supplies for up to 2,160 people in the event of nuclear warfare or other catastrophe. The building was listed on the National Register of Historic Places in 1999.
The Armijska Ratna Komanda D-0, also known as the Ark, ARK/D-0, Atomska Ratna Komanda, and nicknamed Tito's bunker, is a Cold War-era nuclear bunker and military command centre located near the town of Konjic in Bosnia and Herzegovina. Built to protect Yugoslav President Josip Broz Tito and up to 350 members of his inner circle in the event of an atomic conflict, the structure is made up of residential areas, conference rooms, offices, strategic planning rooms, and other areas. The bunker remained a state secret until after the breakup of Yugoslavia in the 1990s.
1. abmm.org: Australian Bunker And Military Museum
2. BunkerBlog: All about German fortifications 1933-1945
3. Bunkersite.com: About bunkers built by the Germans during 1933–1945 in the whole of Europe
4. German bunkers in Poland: Fortified Front Odra-Warta rivers, Boryszyn Loop