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Air raid shelter
Air raid shelter
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One of the London deep-level shelters, in Belsize Park
Kleines Berlin (transl. Little Berlin) is the complex of underground air-raid tunnels dating to World War II, which still exists in Trieste, Italy

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 (but many have been used as defensive structures in such situations).[citation needed]

History

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Pre-WWII

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Prior to World War II, in 1924, an Air Raid Precautions Committee was set up in the United Kingdom. For years, little progress was made with shelters because of the apparently irreconcilable conflict between the need to send the public underground for shelter and the need to keep them above ground for protection against gas attacks. In 1935, every city in the country was given a document to prepare air raid shelters.[1] In February 1936 the Home Secretary appointed a technical Committee on Structural Precautions against Air Attack.

By November 1937, there had only been slow progress, because of a serious lack of data on which to base any design recommendations and the Committee proposed that the Home Office should have its own department for research into structural precautions, rather than relying on research work done by the Bombing Test Committee to support the development of bomb design and strategy. This proposal was eventually implemented in January 1939.[2]

During the Munich crisis, local authorities dug trenches to provide shelter. After the crisis, the British Government decided to make these a permanent feature, with a standard design of precast concrete trench lining. Unfortunately these turned out to perform very poorly. They also decided to issue free to poorer households the Anderson shelter, and to provide steel props to create shelters in suitable basements.[3]

World War II

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During World War II, many types of structures were used as air raid shelters, such as cellars, Hochbunker (in Germany), basements, and underpasses. Bombing raids during World War I led the UK to build 80 specially adapted London Underground stations as shelters. However, during World War II, the government initially ruled out using these as shelters. After Londoners flooded into underground stations during The Blitz, the government reversed its policy. The UK began building street communal shelters as air raid shelters in 1940. Anderson shelters, designed in 1938 and built to hold up to six people, were in common use in the UK. Indoor shelters known as Morrison shelters were introduced as well.

Air raid shelters are still in use to some extent in various nations such as Spain, Switzerland, Israel, Singapore and Taiwan.

Air raid shelters were built to serve as protection against enemy air raids. Existing edifices designed for other functions, such as underground stations (tube or subway stations), tunnels, cellars in houses or basements in larger establishments and railway arches, above ground, were suitable for safeguarding people during air raids.[4] A commonly used home shelter known as the Anderson shelter would be built in a garden and equipped with beds as a refuge from air raids.[5]

Types

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Trenches

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Air raid trenches are forms of trenches that began to be constructed for defensive purposes around the world after the creation of bomber aircraft.[6][7] They were especially prevalent during World War II, but have also been used in other wars.[8][9]

Cellars

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Single-person air raid shelter on display at the Günter Leonhardt aviation museum near Hanover, Germany

Cellars have always been much more important in Continental Europe than in the United Kingdom and especially in Germany almost all houses and apartment blocks have been and still are built with cellars. Air-raid precautions during World War II in Germany could be much more readily implemented by the authorities than was possible in the UK. All that was necessary was to ascertain that cellars were being prepared to accommodate all the residents of a building; that all the cellar hatch and window protections were in place; that access to the cellars was safe in the event of an air raid; that once inside, the occupants were secure for any incidents other than direct hits during the air raid and that means of escape was available.

The inadequacies of cellars and basements became apparent in the firestorms during the incendiary attacks on the larger German inner cities, especially Hamburg and Dresden. When burning buildings and apartment blocks above them collapsed in the raging winds (which could reach well over 800 °C or 1,470 °F), the occupants often became trapped in these basement shelters, which had also become overcrowded after the arrival of inhabitants from other buildings rendered unsafe in earlier attacks. Some occupants perished from heat stroke or carbon monoxide poisoning.

Hochbunker

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The Hochbunker in Trier
Winkelturm in Wünsdorf, Brandenburg

Hochbunker (lit.'high-rise bunkers' or blockhouses), were a type of construction designed to relieve the pressure Nazi German authorities were facing to accommodate additional numbers of the population in high-density housing areas, as well as pedestrians on the streets during air raids. In contrast to other shelters, these buildings were considered completely bomb-proof. They had the advantage of being built upward, which was much cheaper than downward excavation. Hochbunker usually consisted of large concrete blocks above ground with walls between 1 and 1.5 metres (3 ft 3 in and 4 ft 11 in) thick and with huge lintels above doorways and openings. They often had a constant interior temperature of 7 to 10 °C (45 to 50 °F), which made them perfectly suitable for laboratories, both during and after the war. They were used to protect people, administrative centres, important archives and works of art.[citation needed]

Their structures took many forms: usually consisting of square blocks or of low, long rectangular or triangular shapes; straight towers of a square plan rising to great heights, or round tower-like edifices, even pyramidal constructions. Some of the circular towers contained helical floors that gradually curved their way upward within the circular walls. Many of these structures may still be seen. They have been converted into offices, storage space; some have even been adapted for hotels, hospitals and schools, as well as many other peacetime purposes. In Schöneberg, a block of flats was built over the Pallasstrasse air-raid shelter after World War II. During the Cold War, NATO used the shelter for food storage.[10][11]

The cost of demolishing these edifices after the war would have been enormous, as the attempts at breaking up one of the six so-called Flak towers of Vienna proved. The attempted demolition caused no more than a crack in one of the walls of the tower, after which efforts were abandoned. Only the Zoo Tower in Berlin was successfully demolished.[12]

One particular variant of the Hochbunker was the Winkelturm, named after its designer, Leo Winkel of Duisburg. Winkel patented his design in 1934, and from 1936 onward, Germany built 98 Winkeltürme of five different types. The towers had a conical shape with walls that curved downward to a reinforced base. The dimensions of the towers varied. Diameters ranged between 8.4 and 10 metres (28 and 33 ft) and the height between 20 and 25 metres (66 and 82 ft). The walls of the towers had a minimum thickness for reinforced concrete of 0.8 metres (2 ft 7 in) and 1.5 metres (4 ft 11 in) for ordinary concrete. The towers were able to shelter between 164 and 500 people, depending on the type. The intent with the Winkeltürme and the other Hochbunker was to protect workers in rail yards and industrial areas. Because of their shape, the towers became known colloquially as "cigar stubs" or "sugar beets".[citation needed]

The theory behind the Winkeltürme was that the curved walls would deflect any bomb hitting the tower, directing it down towards the base. The towers had a small footprint, which was probably a greater protection. A US bomb did hit one tower in Bremen in October 1944; the bomb exploded through the roof, killing five people inside.

Israel

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Miklat (Hebrew: מקלט, lit.'protected place') Is a type of air raid shelters found in Israel inside homes, near residential areas and in other places across the country.

These places are also called Merkhav Mugan (Hebrew: מרחב מוגן, lit.'protected space'). They are reinforced security rooms required in all new buildings by Israeli law.

Types

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  • Miklat Tzibury (מקלט ציבורי) – lit.'public shelter', a partly underground facility, installed in residential areas. They are commonly used for community needs (clubs, education etc.). Maintained by the local governance and Home Front. They are located in streets and near public facilities.[13]
Public miklat in Holon
  • Miklat BeBayit Meshutaf (מקלט בבית משותף) – lit.'shelter' in a condominium, a facility built into a building which has been declared as a condominium (commonly in a low-rise building) it includes all the facilities that a public shelter has, but is maintained by the building residents.
  • Merkhav Mugan Dirati (מרחב מוגן דירתי or ממ״ד) – installed in residential apartments and private houses.
  • Merkhav Mugan Komati (מרחב מוגן קומתי or ממ״ק) – common floor space in apartment buildings in which there is no Merkhav Mugan Dirati in every apartment and in other multi-storey buildings (mostly offices and industry).
  • Merkhav Mugan Mosadi (מרחב מוגן מוסדי or ממ״מ) – installed in every public structure.

United Kingdom

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Cellars

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Cellars in the UK, were mainly included only in larger houses, and in houses built up to the period of World War I, after which detached and semi-detached properties were constructed without cellars, usually to avoid the higher building costs entailed. Since house building had increased vastly between the wars, the lack of cellars in more recent housing became a major problem in the Air Raid Precautions (ARP) programmes in the UK during World War II.

Alternatives had to be found speedily once it became clear that Germany was contemplating air raids as a means of demoralising the population and disrupting supply lines in the UK. Initial recommendations were that householders should shelter under the stairs. Later, authorities supplied materials to households to construct communal street shelters and Morrison and Anderson shelters.[citation needed]

Basements

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Basements also became available for the use of air raid shelters. Basements under factory premises, schools, hospitals, department stores and other businesses were utilised. However, these ad hoc shelters could bring additional dangers, as heavy machinery and materials or water storage facilities above the shelter, and insufficient support structures threatened to cause the collapse of basements.

When the Wilkinson's Lemonade factory in North Shields received a direct hit on Saturday, 3 May 1941 during a German attack on the north-east coast of England, 107 occupants lost their lives when heavy machinery fell through the ceiling of the basement in which they were sheltering.[14][15]

Railway arches and subways (underpasses)

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British cities prepared for use of railway arches and underpasses in 1935[1] and railway arches and subways[1] were operationalised in the UK for air raid protection during World War II.

Railway arches were deep, curved structures of brick or concrete, set into the vertical sidewalls of railway lines, which had been intended originally for commercial depots, etc. The arches were covered usually with wooden or brick screen- or curtain walls, thus giving a considerable amount of protection against air raids – provided, of course, that railway lines were not the prime target of the attack at the particular time and so being more likely to suffer from direct hits. Each arch could accommodate anything from around 60 to 150 people. However, fewer people could find shelter at night as sleeping areas for the occupants took up more of the space available – a limitation applying to any other type of shelter as well. Subways were actual thoroughfares also in the shape of arches, normally allowing passage underneath railway lines.[16][17]

London Underground stations

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Prior to the beginning of the war, shelter policy had been determined by John Anderson, then Lord Privy Seal and, on the declaration of war, Home Secretary and Minister of Home Security. Anderson announced the policy to Parliament on 20 April 1939,[18] based on a report from a committee chaired by Lord Hailey. This reaffirmed a policy of dispersal and eschewed the use of deep shelters, including the use of tube stations and underground tunnels as public shelters. Reasons given were the spread of disease due to the lack of toilet facilities at many stations, the inherent danger of people falling onto the lines, and that people sheltering in the stations and tunnels might be tempted to stay in them day and night because they would feel safer there than outside the stations.

None of these concerns had been borne out by experience during the bombing raids of the First World War, when eighty specially adapted tube stations had been pressed into use, but in a highly controversial decision in January 1924, Anderson, then chairman of the Air Raid Precautions Committee of Imperial Defence, had ruled out the tube station shelter option in any future conflict.

Following the intensive bombing of London on 7 September 1940 and the overnight raids of 7/8 September, there was considerable pressure to change the policy but, even following a review on 17 September, the government stood firm. On 19 September, William Mabane, parliamentary secretary to the Ministry of Home Security, urged the public not to leave their Anderson shelters for public shelters, saying it deprived others of shelter. "We're going to improve the amenities in existing shelters", he promised. "We're setting about providing better lighting and better accommodation for sleeping and better sanitary arrangements." The Ministries of Home Security and Transport jointly issued an "urgent appeal", telling the public "to refrain from using Tube stations as air-raid shelters except in the case of urgent necessity".

Over the night of 19/20 September, thousands of Londoners took matters in their own hands. They had flocked to the Tubes for shelter, at some stations, they began to arrive as early as 4:00 pm, with bedding and bags of food to sustain them for the night. By the time the evening rush hour was in progress, they had already staked their "pitches" on the platforms. The Police did not intervene and some station managers, on their own initiative, provided additional toilet facilities. Transport Minister John Reith, and the chairman of London Transport, Lord Ashfield, inspected Holborn tube station to see for themselves.

The government realised that it could not contain this popular revolt. On 21 September, it abruptly changed policy, removing its objections to the use of tube stations. In what it called part of its "deep shelter extension policy", it decided to close the short section of Piccadilly line from Holborn to Aldwych, and convert different sections for specific wartime use, including a public air raid shelter at Aldwych. Floodgates were installed at various points to protect the network should bombs breach the tunnels under the Thames, or large water mains in the vicinity of stations. Seventy-nine stations were fitted with bunks for 22,000 people, supplied with first aid facilities and equipped with chemical toilets. 124 canteens opened in all parts of the tube system. Shelter marshals were appointed, whose function it was to keep order, give first aid and assist in case of the flooding of the tunnels.

London Underground station in use as an air-raid shelter during World War II

Businesses (for example Plessey Ltd) were allowed to use the Underground stations and unopened tunnels; government offices were installed in others and the anti-aircraft centre for London used a station as its headquarters. Tube stations and tunnels were still vulnerable to a direct hit and on 14 October 1940, a bomb penetrated the road and tunnel at Balham tube station, blew up the water mains and sewage pipes, and killed 66 people. At Bank station, a direct hit caused a crater of 37 by 30 metres (120 ft × 100 ft) on 11 January 1941; the road above the station collapsed and killed 56 occupants. The highest death toll was caused by an incident at the unfinished Bethnal Green tube station on 8 March 1943, when 1,500 people entered the station. The crowd suddenly surged forward upon hearing the unfamiliar sound of a new type of anti-aircraft rocket being launched nearby. Someone stumbled on the stairs, and the crowd pushing on, were falling on top of one another, and 173 people were crushed to death in the disaster.

The London Underground system was considered one of the safest means of protecting relatively many people in a high-density area of the capital. An estimated 170,000 people sheltered in the tunnels and stations during the war. Although not a great number in comparison to the population of the capital, it almost certainly saved the lives of the people who probably would have had to find alternative, less secure means of protection.[19] Artists and photographers such as Henry Moore and Bill Brandt were employed as war artists to document life in London's shelters during the war.[20]

Other tunnels

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The Victoria tunnels, offered air raid shelter.
External videos
video icon By 1935... the government stated, every city should have air raid protection.[1]

Many other types of tunnels were adapted for shelters to protect the civil population, and the military and administrative establishment in the UK during the war. Some had been built many years before, some had been part of an ancient defence system, and some had belonged to commercial enterprises, such as coal mining.

The Victoria tunnels at Newcastle upon Tyne, for example, completed as long ago as 1842, and used for transporting coal from the collieries to the river Tyne, had been closed in 1860 and remained so until 1939. In places the tunnels were 12 metres (39 ft) deep, the tunnels, stretching in parts beneath the city of Newcastle, were converted to air raid shelters with a capacity for 9,000 people.[1] Tunnels linked to landing stages built on the River Irwell in Manchester at the end of the nineteenth century were also used as air-raid shelters.

The medieval labyrinth of tunnels beneath Dover Castle had been built originally as part of the defensive system of the approaches to England, extended over the centuries and further excavated and reinforced during the world wars, until it was capable of accommodating large parts of the secret defence systems protecting the British Isles. On 26 May 1940, it became the headquarters under Vice Admiral Bertram Ramsay of Operation Dynamo, from which the rescue and evacuation of up to 338,000 troops from France was directed.

In Stockport, 6 mi (9.7 km) south of Manchester, four sets of underground air raid shelter tunnels for civilian use were dug into the red sandstone on which the town centre stands. Preparation started in September 1938 and the first set of shelters was opened on 28 October 1939. (Stockport was not bombed until 11 October 1940.) The smallest of the tunnel shelters could accommodate 2,000 people and the largest 3,850 (subsequently expanded to take up to 6,500 people.) The largest of the Stockport Air Raid Shelters are open to the public as part of the town's museum service.[21]

In southeast London, residents made use of the Chislehurst Caves beneath Chislehurst, a 35-kilometre-long (22 mi) network of caves which have existed since the Middle Ages for the mining of chalk and flint.

Street communal shelter

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In the United Kingdom, public shelters in open spaces, especially near streets, were needed for pedestrians, drivers and passengers in passing vehicles, etc. The programme of building street communal shelters commenced in March 1940, the government supplying the materials, and being the moving force behind the scheme, and private builders executing the work under the supervision of surveyors. These shelters consisted of 360-millimetre (14 in) brick walls and 300-millimetre-thick (1 ft) reinforced concrete roofs, similarly to, but much larger than, the private shelters in backyards and gardens being introduced slightly later. The communal shelters were usually intended to accommodate about fifty persons, and were divided into various sections by interior walls with openings connecting the different sections. Sections were normally furnished with six bunks.[citation needed]

The construction work then went on rapidly, until the resources of concrete and bricks began to be depleted due to the excessive demand placed on them so suddenly. Also, the performance of the early street shelters was a serious blow to public confidence. Their walls were shaken down either by earth shock or blast, and the concrete roofs then fell onto the helpless occupants, and this was there for all to see.[22][page needed] At around the same time rumours of accidents started to circulate, such as on one occasion people being drowned due to a burst main filling up the shelter with water. Although much improved designs were being introduced whose performance had been demonstrated in explosion trials, communal shelters became highly unpopular, and shortly afterwards householders were being encouraged to build or have built private shelters on their properties, or within their houses, with materials being supplied by the government.[citation needed]

Anderson shelter

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An unburied Anderson shelter in 2007, showing the distinctive curved shape of its walls; this shelter had seen use after the war as a shed
Children preparing to sleep in the Anderson shelter installed in their garden during frequent bombing raids on Bournemouth in 1941

The Anderson shelter was designed in 1938 by William Paterson and Oscar Carl (Karl) Kerrison in response to a request from the Home Office. It was named after Sir John Anderson, then Lord Privy Seal with special responsibility for preparing air-raid precautions immediately prior to the outbreak of World War II, and it was he who then initiated the development of the shelter.[23][24] After evaluation by David Anderson, Bertram Lawrence Hurst, and Sir Henry Jupp, of the Institution of Civil Engineers, the design was released for production.

Anderson shelters were designed to accommodate up to six people. The main principle of protection was based on curved and straight galvanised corrugated steel panels. Six curved panels were bolted together at the top, so forming the main body of the shelter, three straight sheets on either side, and two more straight panels were fixed to each end, one containing the door—a total of fourteen panels. A small drainage sump was often incorporated in the floor to collect rainwater seeping into the shelter.

The shelters were 1.8 metres (6 ft) high, 1.4 metres (4.5 ft) wide, and 2.0 metres (6.5 ft) long. When installed underground, they were buried 1.2 metres (4 ft) deep in the soil and then covered with a minimum of 38 centimetres (15 in) of soil above the roof. When they were buried outside, the earth banks could be planted with vegetables and flowers, that at times could be quite an appealing sight and in this way would become the subject of competitions of the best-planted shelter among householders in the neighbourhood. The internal fitting out of the shelter was left to the owner and so there were wide variations in comfort.[5]

Anderson shelters were issued free to all householders who earned less than £5 a week (equivalent to £390 in 2023, when adjusted for inflation). Those with a higher income were charged £7 (£550 in 2023) for their shelter. One and a half million shelters of this type were distributed between February 1939 and the outbreak of war. During the war a further 2.1 million were erected.[25] Large numbers were manufactured at John Summers & Sons ironworks at Shotton on Deeside with production peaking at 50,000 units per week.[26]

The Anderson shelters performed well under blast and ground shock, because they had good connectivity and ductility, which meant that they could absorb a great deal of energy through plastic deformation without falling apart. (This was in marked contrast to other trench shelters which used concrete for the sides and roof, which were inherently unstable when disturbed by the effects of an explosion – if the roof slab lifted, the walls fell in under the static earth pressure; if the walls were pushed in, the roof would be unsupported at one edge and would fall.) However, when the pattern of all-night alerts became established, it was realised that in winter Anderson shelters installed outside were cold damp holes in the ground and often flooded in wet weather, and so their occupancy factor would be poor. This led to the development of the indoor Morrison shelter.[22][page needed]

At the end of the war in Europe, households who had received an Anderson shelter were expected to remove their shelters and local authorities began the task of reclaiming the corrugated iron. Householders who wished to keep their Anderson shelter (or more likely the valuable metal) could pay a nominal fee.

Because of the large number made and their robustness, many Anderson shelters still survive. Many were dug up after the war and converted into storage sheds for use in gardens and allotments.[27][24]

Morrison shelter

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A couple demonstrating the use of a Morrison shelter

The Morrison shelter, officially termed Table (Morrison) Indoor Shelter, had a cage-like construction beneath it. It was designed by John Baker and named after Herbert Morrison, the Minister of Home Security at the time. It was the result of the realisation that due to the lack of house cellars it was necessary to develop an effective type of indoor shelter. The shelters came in assembly kits, to be bolted together inside the home. They were approximately 1.98 metres (6 ft 6 in) long, 1.2 metres (4 ft) wide and 0.76 metres (2 ft 6 in) high, had a solid 3.2 millimetres (18 in) steel plate "table" top, welded wire mesh sides, and a metal lath "mattress"-type floor. Altogether it had 359 parts and had three tools supplied with the pack.

The shelter was provided free to households whose combined income was less than £400 per year (equivalent to £31,000 in 2023).

Head of the Engineering Department at Cambridge University, Professor John Baker (later Lord Baker) presented an undergraduate lecture on the principles of design of the shelter as an introduction to his theory of plastic design of structures, which can be summarised as follows:

It was impractical to produce a design for mass production that could withstand a direct hit, and so it was a matter of selecting a suitable design target that would save lives in many cases of blast damage to bombed houses. Examination of bombed buildings indicated that in many instances, one end wall of a house was sucked or blown out by a nearby blast, and the floor of the first storey pivoted about its other end (supported by a largely intact wall) and killed the inhabitants. The Morrison shelter was therefore designed to be able to withstand the upper floor falling, of a typical two storey-house undergoing a partial collapse. The shelter was designed to absorb this energy by plastic deformation, since this can absorb two or three orders of magnitude more energy than elastic deformation.[28] Its design enabled the family to sleep under the shelter at night or during raids, and to use it as a dining table in the daytime, making it a practical item in the house.[29]

Half a million Morrison shelters had been distributed by the end of 1941, with a further 100,000 being added in 1943 to prepare the population for the expected German V-1 flying bomb (doodlebug) attacks.

In one examination of 44 severely damaged houses it was found that 3 people had been killed, 13 seriously injured, and 16 slightly injured out of a total of 136 people who had occupied Morrison shelters; thus 120 out of 136 escaped from severely bomb-damaged houses without serious injury. Furthermore, it was discovered that the fatalities had occurred in a house which had suffered a direct hit, and some of the severely injured were in shelters sited incorrectly within the houses.[30]

In July 1950, the Royal Commission on Awards to Inventors made an award of £3,000 (£130,000) to Baker for his design of the Morrison shelter.[31]

In 1981, the British government would issue a series of Domestic Nuclear Shelters publications to complement the earlier Protect and Survive pamphlet. One of the shelters depicted in Domestic Nuclear Shelters, the Type 2 indoor shelter, was mostly identical to the Morrison shelter, and the assembly instructions were essentially the same as those contained in the 1941 How to Put Up Your Morrison 'Table' Shelter pamphlet.[32]

Scallywag bunkers

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Reconstruction of a Scallywag bunker at Parham Airfield Museum, Suffolk

Scallywag bunkers or Operational Base (OB) were underground bunkers used by Auxiliary Units of the British Resistance against axis invasion of the United Kingdom. They were provided with elaborately concealed underground Operational Bases, usually built by the Royal Engineers in a local woodland, with a camouflaged entrance and emergency escape tunnel.

Stanton shelters

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An abandoned Stanton shelter at the disused airfield RAF Beaulieu (2007)

A segment shelter manufactured by the Stanton Ironworks, Ilkeston, Derbyshire. The shop producing spun-concrete lighting columns ceased production and turned over to concrete air-raid shelters, of which 100,000 tonnes (220 million pounds) were manufactured, principally for the air ministry. Reinforced concrete proved an ideal material for air-raid shelters, being strong and resistant to shock with no deterioration with the passing of time. This type of segment shelter was of simple design and of low cost—any length of shelter could be built up from the pre-cast steel reinforced concrete segments.

The segments were 510 millimetres (20 in) wide; a pair of them formed an arch 2.1 metres (7 ft) high and transverse struts were provided to ensure rigidity. These fitted into longitudinal bearers which were grooved to receive the foot of each segment. Each pair of segments was bolted together at the apex of the arch and each segment was also bolted to its neighbour, the joints being sealed with a bituminous compound. The convenient handling of these segments enabled them to be transported onto sites where close access by motor lorry was not possible. Partly buried in the ground, with a suitably screened entrance, this bolted shelter afforded safe protection against blast and splinters.[33][34]

Other construction

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German anti-aircraft shelter from the Second World War at the shipyard in Gdańsk was built without a basement due to the presence of groundwater

Some air-raid shelters were constructed in residential building schemes in anticipation of the Second World War. There is a surviving example at St Leonard's Court in East Sheen, southwest London.

Military air-raid shelters included blast pens at airfields for the security of aircrews and aircraft maintenance personnel away from the main airbase buildings.

Few shelters could survive a direct bomb-hit. The German authorities claimed that Hochbunker were totally bomb-proof, but none were targeted by any of the 41 10,000-kilogram (22,000 lb) Grand Slam earthquake bombs dropped by the RAF by the end of World War II. Two of these bombs were dropped on the U-Bootbunkerwerft Valentin submarine pens near Bremen and these barely penetrated 4 to 7 metres (13 to 23 ft) of reinforced concrete, bringing down the roof.

More recently, the penetration by laser-guided "smart bombs" of the Amiriyah shelter during the 1991 Gulf War showed how vulnerable even reinforced concrete shelters are to direct hits from bunker-buster bombs. However, the air-raid shelters are built to protect the civilian population, so protection against a direct hit is of secondary value. The most important dangers are the blast and shrapnel.

Air-raid shelters in modern times

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Old air-raid shelters, such as the Anderson, can still be found in back gardens, in which they are commonly used as sheds, or (on a roof covered with earth) as vegetable patches.

Countries which have kept air-raid shelters intact and in ready condition include Switzerland, Spain and Finland.

Switzerland

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Many Swiss houses and apartment blocks still have structurally reinforced, underground basements, often featuring a concrete door around 40 cm (16 in) thick. In more modern, post-war times, these shelters are often used as storage, with the footprint of the reinforced basement divided up into individual storage units according to the number of apartments in the house. The basement shelters are built to more stringent building codes, as the ceiling especially should protect shelter-seeking people from the house collapsing. Although most Swiss houses provide their own shelters, those that do not are required by law to post directions to the nearest shelter.

Spain

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Barcelona was severely bombed by Italian and German Air Forces during Spanish Civil War, particularly in 1937 and 1938. Tunnels were used as shelters at the same time that the population undertook the building of bomb shelters under the coordination of a committee for civil defense (Catalan: Junta de defensa passiva) providing planning and technical assistance. Hundreds of bomb shelters were built. Most of them are recorded, but only a few are well preserved. Among these stand out the Plaça del Diamant refuge as well as air-shelter 307 (Refugi 307), today one of the Barcelona City History Museum heritage sites.[35]

Other cities with extant bomb shelters from the Spanish Civil War include Madrid, Guadalajara, Alcalá de Henares, Santander, Jaén, Alcañiz, Alcoy, Alicante, Almería, Valencia and Cartagena. During the war, Cartagena, an important naval base, was one of the main targets for Franco's bombers. Cartagena suffered between 40 and 117 bombings (sources are mixed about the number of attacks). The most dramatic was one carried out by the German Condor Legion on 25 November 1936. The largest air raid shelter in Cartagena, which could accommodate up to 5,500 people, has been a museum since 2004.[36]

Israel

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The inside of an Israeli bomb shelter in 2012

The State of Israel required all buildings to have access to air-raid shelters from 1951, and all new flats possess access to Merkhav Mugan (in-building protected spaces). All medical and educational facilities are prepared for chemical, biological, radiological and nuclear (CRBN) attacks as of 2010 – for example, each surgery room is built to withstand a direct missile hit – some are built with closed-cycle air systems and are capable of being resistant to chemical agents for short periods of time; in addition all must include chemical air filtering systems. The public air-raid shelters are commonly employed as game rooms in peacetime so that the children will be comfortable to enter them at a time of need, and will not be frightened.[37][38][39][40][41]

Finland

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A normal Finnish S1-shelter steel door; 'S' is short for suoja (protection, shelter)

The Ministry of Interior, responsible for civil defence in Finland, maintains hard shelters, capable of accommodating 3.6 million persons, in cities and in other densely populated areas where two-thirds of the country's population live. They are built to withstand the detonation of a 100-kilotonne-of-TNT (420 TJ) nuclear bomb at ground zero.[42] In total Finland has over 45,000 civil defence shelters which can house 3.6 million people[43] (65% of the population). A shelter is designed to protect the population in the event of a threat of a possible gas or poison leak, armed attack such as war, radioactive fallout, or the like. Private homes rarely have them, but houses over 1,200 square metres (13,000 sq ft) are obliged to build them.[43] Fire inspectors check the shelters every ten years and flaws have to be repaired or corrected as soon as possible. Shelters are often used as storage spaces but the law requires that inhabitants of apartment blocks must be able to clear the shelters and put them into action in less than 72 hours. Half of the air-raid shelter has to be ready to use in two hours. The types of shelters are:

  • K, a small shelter for a small apartment house.
  • S1, a usual shelter for apartment house.
  • S3, lightweight shelter in solid rock or heavyweight shelter of ferroconcrete.
  • S6, large shelters in solid rock that must be able to withstand a 6-bar (600 kPa) pressure wave.

All shelters must have:[44]

  • an electric and hand-operated air-conditioning system, which can protect from biological and chemical weapons and radioactive particles.
  • a radiometer
  • dry toilets
  • a fixed-line telephone interface
  • a spare exit
  • water tanks
  • a first aid kit

Singapore

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Since 1998, Singapore has required all new houses and flats to have a shelter built to certain specifications. The Singapore Civil Defence Force rationalizes building such shelters in high-rise buildings by noting that weapon effects tend to be localized, and are unlikely to cause an entire building to collapse.[45]

Taiwan

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There are currently 117,669 air raid shelters in Taiwan. The first air raid shelters were constructed in the Japanese colonial period and construction expanded during WWII as allied bombers began hitting Taiwan.[46]

Greece

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During the pre-WW2 period the Metaxas regime initiated an extensive Civil Defence system designed to protect civilians in the event of enemy bombing.[47] The system included extensive training of civilians as well as the construction of more than 12,000 air raid shelters in Attica, equipped with German made blast doors and air filtering systems. From 1939 forward virtually all new apartment buildings contained built-in hardened basements and cellars that functioned as (unofficial) bunkers, although these lacked the more sophisticated equipment of the state built shelters.[48][49][50][51]

After the war, most of these shelters were either abandoned or demolished along with the apartment buildings they were built in. Public shelters were covered to make way for the modern street network. The last public inspection of the remaining shelters was performed in the 70s. Nowadays very few state built shelters remain intact, although hardened cellars still remain in the basements of most buildings in the older districts of Thessaloniki and Athens.[52][53][54][55]

Notable surviving shelters include the Likavitos shelter, built inside the mountain of the same name, the Ministry of Finance bunker and the Piraeus bunkers in Athens,[56] and the nuclear bunker under the Military Hospital no 414 in Thessaloniki.[57][58][59]

Ukraine

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Residents sheltering in a Kyiv Metro station during the 2022 Russian invasion of Ukraine.

The Kyiv Metro was built in the wake of World War II.[60] During the 2022 Russian invasion of Ukraine, the metro stations doubled as bomb shelters, as residents took shelter from Russian bombs.[61] Like other former Soviet metro systems, the Kyiv metro was designed with this purpose in mind, and 47 of the city's 52 stations were designated for this purpose.[62] During the invasion, on 24 February 2022, regular service on the metro was suspended.[63] A reduced schedule was adopted with limited services running between 8 am and 7 pm. All underground stations remain open 24 hours a day to provide shelter.[64] According to Kyiv's mayor Vitali Klitschko, on 2 March 2022, as many as 150,000 residents of Kyiv sought shelter in the Metro.[65] Stations in the Kharkiv Metro were also used as shelters.

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See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia
from Grokipedia
An air raid shelter is a fortified structure engineered to shield civilians from the destructive forces of aerial bombardment, including explosive blasts, flying debris, and structural collapses. Developed in response to early 20th-century air raids, such as those by Zeppelins in , they proliferated during amid intensive bombing campaigns like on Britain and strategic strikes across . In Britain, over 3.6 million Anderson shelters—corrugated units partially buried and earthed over—were distributed to households with gardens, capable of accommodating up to six and withstanding indirect hits from 100-pound bombs if correctly installed, though prone to dampness and flooding. Indoor alternatives like the Morrison shelter, a -mesh table-like cage for apartments, offered limited lateral protection for small families but proved less robust against nearby detonations. Public options included surface communal bunkers and deep underground facilities, such as London's repurposed Tube stations that housed up to 170,000 nightly, providing superior blast resistance but risking overcrowding and sanitation issues. While shelters demonstrably mitigated casualties in many instances by deflecting shrapnel and absorbing shocks, their efficacy depended on design, construction quality, and proximity to direct hits, with surface types vulnerable to collapse under heavy ordnance. Contemporary variants persist in regions facing missile threats, adapting concrete and reinforcements to counter precision-guided munitions and drones.

History

Origins and Pre-World War II Developments

The concept of air raid shelters emerged from the advent of aerial bombardment in early 20th-century warfare, with the first documented modern air raid occurring on November 1, 1911, when Italian pilot Giulio Gavotti dropped grenades from an aircraft during the . Systematic civilian protection measures developed during , prompted by German raids on Britain beginning January 19, 1915, which targeted coastal towns and , resulting in over 50 raids that killed approximately 557 civilians and injured 1,343 by war's end. Initial responses relied on ad hoc refuges such as basements, cellars, and stations, which sheltered up to 300,000 people during alerts, alongside natural formations like caves and arches. One of the earliest purpose-built shelters appeared in 1916 at , , constructed from after a raid killed local residents and soldiers; this single-room structure, 4 meters wide and 5 meters deep with protective lobbies, represented an early engineering effort to shield civilians from blast and shrapnel. British government actions during the war prioritized anti-aircraft defenses and fighter interception over widespread shelter construction, reflecting underestimation of sustained aerial threats to non-combatants, though public demand drove improvised protections that influenced later designs. In the , lingering WWI experiences informed theoretical planning, such as a 1924 subcommittee, but political reluctance and budget constraints delayed implementation amid hopes that international agreements would avert future conflicts. Renewed urgency arose in the 1930s from observations of the (1936–1939), where Republican cities faced intensive aerial campaigns by German and Italian forces, including the on April 26, 1937, which killed hundreds and highlighted vulnerabilities of urban populations. In alone, over 1,000 public shelters were excavated by 1938 using zigzag tunnels and the resilient technique to deflect blasts, accommodating civilians during 385 attacks that dropped nearly 2,000 bombs and caused 2,700 deaths; these community-led efforts, coordinated by engineers like Ramon Perera, reduced casualties through basic ventilation, lighting, and sanitation features. Britain's preparations accelerated with the Air Raid Precautions Act of 1937, establishing warden services and mandating local authorities to organize defenses, followed by the distribution of the first household shelters in 1938 amid fears of gas and high-explosive attacks. The Anderson shelter, a corrugated steel design by engineer William Paterson intended for garden burial to withstand 900-pound bombs, was prototyped in 1938 and first erected on February 25, 1939, in , , with over 1.5 million units issued to qualifying households by September 1939 under the oversight of Sir John Anderson. These developments, informed by Spanish precedents studied by figures like , marked a shift toward standardized, mass-produced protections, though debates persisted over deep versus surface shelters, with official reports like the Hailey inquiry rejecting extensive underground networks due to cost and disruption concerns.

World War II Era

The onset of in prompted rapid expansion of air raid shelter programs, particularly in nations anticipating aerial bombardment. In the , the government had begun distributing Anderson shelters—semi-cylindrical structures made of corrugated galvanized steel sheets buried in gardens—starting February 1939, with 1.5 million units issued before the war's outbreak to provide protection against blasts and shrapnel. By the end of production, approximately 3.6 million Anderson shelters had been manufactured, distributed free to households earning under £250 annually and sold for £7 to others, accommodating families in a space roughly 6 feet long, 4 feet wide, and 6 feet high when covered with earth for and reinforcement. These shelters were engineered to withstand direct hits from bombs up to 100 pounds detonating within 6 feet, though they often suffered from dampness and inadequate ventilation during prolonged use. As the Blitz intensified from September 1940, with raids devastating and other cities, indoor alternatives like the Morrison shelter—a robust steel table-like cage measuring about 6.5 feet long, 4 feet wide, and 2.5 feet high—were introduced in 1941 for urban dwellers lacking garden space. Over 500,000 Morrison shelters were distributed by late 1941, designed to shield occupants from collapsing ceilings while doubling as furniture. Public facilities, including reinforced street shelters and stations, sheltered millions nightly; by November 1940, eight deep-level bomb-proof stations were authorized, housing up to 120 people per platform section amid overcrowding and poor sanitation. Tragically, a panic at station in March 1943 resulted in 173 deaths, highlighting risks of mass sheltering without adequate exits or . In , facing Allied bombing campaigns from 1942 onward, authorities constructed thousands of Hochbunker—above-ground fortresses with walls up to 3 meters thick—starting in the mid-1930s, such as the 38-meter-high bunker completed for local officials and civilians. These multi-story structures, often integrated with flak towers, could protect 25,000 people in facilities like Hamburg's Feldstrasse bunker during intense raids, prioritizing blast resistance over burial. By war's end, such bunkers demonstrated trade-offs: superior durability against high-explosive bombs but vulnerability to incendiaries and resource-intensive construction amid labor shortages.

Post-World War II and Cold War Period

Following , many air raid shelters from the conflict were decommissioned or repurposed as conventional bombing threats diminished, but the onset of the and the advent of nuclear weapons prompted renewed emphasis on protective structures adapted for blast, heat, and radioactive fallout. In the United States, civil defense programs shifted focus to fallout shelters designed to shield occupants from radiation for up to two weeks, with supplies like water, food, and medical kits mandated for stocking. By 1961, amid heightened tensions after events like the , allocated over $169 million to identify and equip existing public buildings as shelters, prioritizing basements in schools, hospitals, and government facilities. This effort marked over 18,000 public sites by the mid-1960s, though private backyard bunkers also proliferated among affluent families, reflecting public anxiety over scenarios. Switzerland exemplified comprehensive national preparation, mandating shelters in its 1959 federal constitution and enacting a 1963 law requiring nuclear-resistant bunkers in all new residential and commercial buildings. This policy resulted in over 370,000 shelters by the late , providing hardened space for the entire population of approximately 8 million, far exceeding per capita coverage in other nations; structures featured walls, independent ventilation with filters, and provisions for extended habitation. The system's rationale stemmed from 's neutrality and geographic vulnerability to spillover from European conflicts, with construction peaking during the 1950s-1970s amid fears of Soviet nuclear strikes. In the , post-1945 shelter construction emphasized metro stations and underground facilities in major cities like , where deep tunnels doubled as and blast-resistant refuges capable of withstanding nuclear ; by the 1950s, programs expanded to include government command bunkers and urban hardened sites, driven by Stalin-era and later Khrushchev policies interpreting Western deterrence as existential threats. , including the , saw less widespread new builds, with many WWII-era Anderson and Morrison shelters abandoned or converted to storage by the 1950s, though regional nuclear bunkers for were maintained until the 1980s. Efficacy debates persisted, as empirical tests showed fallout shelters reduced gamma by factors of 100-1,000 depending on depth and shielding, but critics noted limitations against direct hits or prolonged societal breakdown.

Design and Engineering Principles

Core Protection Mechanisms

The core protection mechanisms of air raid shelters focus on shielding occupants from blast overpressure, flying fragments, and structural collapse induced by conventional aerial bombs, such as the 500-pound high-explosive types prevalent in . These mechanisms operate through energy dissipation via burial or overburden, geometric deflection, and material absorption, with designs standardized to withstand indirect effects at distances of 25 to 50 feet from . Direct hits were rarely survivable in civil structures, as protection prioritized probabilistic threats over absolute penetration resistance. Blast overpressure and dynamic ground shock are primarily mitigated by underground placement or earth cover, which attenuates pressure waves decaying cubically with distance, and by reinforcing against loads of 200 to 400 pounds per square foot from collapsing upper stories. Entrance baffles, minimum 12 inches of or equivalent barriers extending beyond openings, prevent shockwave ingress while maintaining access. Structural elements like roofs of 4.5 to 6 inches in designs further distribute loads, calibrated to resist equivalent static pressures from nearby explosions without total failure. Fragmentation and splinter penetration are countered by lateral walls of 12 inches reinforced concrete (3,000 psi strength), 13 inches reinforced , or 15 inches plain , sufficient to stop debris from a 500-pound at 25 feet. Overhead and side protections incorporate similar thicknesses, often backed by for added inertial resistance. For potential direct impacts, burster slabs of variable depth (up to 5.5 feet for 500-pound s from 20,000 feet altitude) aim to fragment projectiles prematurely, though such features were limited in mass civil shelters due to cost and engineering constraints.

Materials and Construction Techniques

Air raid shelters utilized materials chosen for their capacity to withstand blast overpressure, fragmentation, and structural collapse, with construction techniques emphasizing rapid assembly, burial for earth overburden protection, and reinforcement against dynamic loads. Corrugated galvanized , as in the British Anderson shelter introduced in 1938, consisted of six arched panels approximately 1.6 mm thick, bolted together to form a semi-cylindrical structure weighing about 400 kg, which was partially buried and covered with 0.9 m of earth to absorb shock waves and debris. The steel's zinc coating prevented , while the corrugation enhanced rigidity without excessive weight, enabling homeowner installation in gardens during . Reinforced concrete emerged as a primary material for communal and public bunkers due to its and ability to resist penetration; for instance, wartime shelters often featured pre-cast sectional frames and panels with walls 0.3–0.6 m thick, incorporating steel rebar such as ASTM A615 Grade 60 deformed bars for tensile reinforcement. involved excavating sites, assembling or pouring in situ with , and integrating blast doors; empirical tests showed such structures could endure overpressures up to 0.93 MPa from high-explosive detonations when properly designed. Brick-faced variants with roofs were common in urban street shelters but proved vulnerable, as unreinforced walls tended to crack under from nearby impacts. Post-World War II designs, particularly in Switzerland's program mandated from 1963, relied on cast-in-place for underground bunkers, often with walls exceeding 0.5 m thickness and integrated ventilation shafts, prioritizing long-term durability over wartime expediency. Techniques included modular for speed, as seen in some American bunkers, where sections were transported and bolted or welded on-site to minimize labor. Earth mounding and layering—such as soil, sand, and sod up to 2.4 m total—further dispersed blast energy, a method validated in historical assessments for reducing fragment penetration by up to 50% compared to exposed surfaces. These approaches balanced material availability, cost, and protective efficacy, though dampness from permeation remained a persistent challenge in buried designs requiring drainage provisions.

Ventilation, Sanitation, and Long-Term Habitability

Effective ventilation in air raid shelters was essential to mitigate risks from accumulation, oxygen depletion, and contaminant ingress during confined occupancy. Human respiration generates approximately 0.5 kilograms of CO2 per person per day, necessitating air exchange rates of at least 5-10 cubic meters per person per hour to maintain CO2 below 0.5% and oxygen above 19.5% in enclosed spaces. British WWII shelters typically relied on passive systems, including gratings and shafts providing natural airflow, though overcrowding often reduced efficacy, leading to elevated CO2 levels causing headaches and fatigue. Industrial and deep-level shelters incorporated mechanical fans powered by internal generators, with gas-tight filters for chemical threats, as seen in facilities like Henley's cable works bunkers. German bunkers, such as those in the Atlantic Wall, featured engineered ventilation with blast valves and anti-grenade deflectors on intake vents to prevent while ensuring filtered air supply. Sanitation provisions addressed waste disposal without reliance on municipal sewers, which were vulnerable to disruption. Chemical toilets, such as the Elsan model introduced in the 1920s and widely deployed by 1941, used disinfectants to break down waste in sealed buckets, enabling use in waterless environments like tube stations and communal bunkers accommodating thousands. In London Underground shelters, these facilities were supplemented by first-aid posts, though initial shortages in early Blitz raids (September 1940) forced improvised bucket systems, exacerbating hygiene risks. Overcrowding strained capacity, with reports of inadequate emptying during alerts contributing to odor buildup and potential pathogen spread, including respiratory infections documented in shelter populations. Long-term habitability beyond acute raids—extending to days or weeks in scenarios like sustained sieges or fallout—demanded integrated systems beyond basic protection, but most WWII designs prioritized blast resistance over endurance. Ventilation failures in unpowered states could lead to rapid air quality degradation; for instance, gravity-based systems in underground shelters provided minimal flow (0.1-0.5 air changes per hour), insufficient for groups exceeding design capacity without manual pumps. Sanitation challenges compounded this, as chemical toilets required periodic servicing, and waste accumulation risked water contamination if not isolated, prompting civil defense guidelines for boiling or chlorination of shelter water supplies. Historical occupancy in British tube shelters revealed limits: while bunks and canteens supported overnight stays for up to 22,000, poor air circulation and sanitation led to disease outbreaks, underscoring that shelters rated for 8-24 hours became untenable without resupply, with empirical data from the Blitz indicating psychological strain from confinement alongside physical degradation. Advanced post-war adaptations, informed by WWII lessons, emphasized redundant power for fans and air revitalization units capable of sustaining 100-person groups for 24 hours by scrubbing CO2.

Types of Air Raid Shelters

Domestic and Indoor Shelters

Domestic and indoor air raid shelters consist of protective enclosures designed for installation and use within homes, particularly suited for urban households lacking gardens or basements suitable for outdoor or subterranean alternatives. These structures prioritize shielding occupants from collapsing ceilings, flying debris, and blast waves generated by nearby explosions, rather than direct impacts. Unlike outdoor variants, indoor shelters emphasize compactness, everyday utility, and rapid deployment inside living spaces. The archetypal indoor shelter emerged in the amid the intensification of bombing campaigns during . Named after , the responsible for civil defense, the Morrison shelter was mass-produced starting in March 1941 to address vulnerabilities in terraced housing prevalent in British cities. Constructed from welded steel mesh panels supported by a robust steel plate tabletop approximately 6 feet 6 inches long, 4 feet wide, and 2 feet 6 inches high, it resembled a reinforced table capable of accommodating two to four adults in a . The design allowed dual functionality: serving as a dining table during peacetime and a refuge during alerts, with the solid top engineered to support the weight of a fallen floor while the mesh sides deflected fragments. Over 1.1 million units were distributed free to low-income households and sold at subsidized rates to others by 1945. Engineering assessments post-war indicated the Morrison shelter's efficacy against indirect hits, with studies of bombed residences revealing survival rates exceeding 80% for properly assembled units amid structural collapses. Its steel framework, weighing around 200 pounds, relied on plastic deformation principles to absorb and redistribute loads from overhead failures, preventing penetration by debris that claimed lives in unsheltered rooms. However, limitations were evident: the enclosure offered minimal protection against direct strikes, fire, or suffocation from smoke, and its low height restricted movement, potentially exacerbating discomfort during prolonged alerts. Ventilation was rudimentary, dependent on ambient room air, and sanitation provisions were absent, necessitating brief occupancy. Beyond the , formalized domestic indoor shelters were less standardized during WWII, with civilians in countries like the often improvising using interior hallways, stairwells, or basements fortified with mattresses and furniture to mitigate blast and shrapnel risks, as recommended by manuals. In , apartment dwellers in nations such as utilized cellar conversions or prefabricated indoor frames, though documentation emphasizes communal over individual home installations. Post-war adaptations for nuclear threats echoed the Morrison model, with governments promoting reinforced indoor spaces stocked for fallout, but these diverged from conventional air raid priorities by focusing on shielding over dynamics.

Outdoor and Garden Shelters

Outdoor and garden shelters are prefabricated or constructible structures designed for private installation in residential yards or gardens, relying on partial burial and earthen overburden to deflect blast waves and shrapnel from aerial bombs. These shelters prioritize affordability and ease of assembly for civilian use, typically accommodating small families while integrating into domestic landscapes for . The archetypal example is the Anderson shelter, developed in the as a response to anticipated air raids. Named after Sir John Anderson, the Minister of , the design emerged in 1938 with the first prototype assembled in , , in February 1939. Over 3.6 million units were produced, with 1.5 million distributed by September 1939 and an additional 2.1 million during ; they were supplied free to households earning less than £250 annually, while others paid £7 (equivalent to approximately £411 in 2023). Anderson shelters consisted of 14 galvanized corrugated panels—eight flat for the sides and six curved for the arched —assembled via bolting to form a semi-cylindrical measuring roughly 2 meters long, 1.4 meters wide, and 1.8 meters high, sufficient for up to six people (typically four adults and two children). Installation required excavating a pit about 1 meter deep in the garden soil, positioning the structure within, and mounding at least 38 centimeters of earth over the for blast absorption and concealment; the corrugations enhanced structural integrity against compressive forces from nearby detonations, while the galvanized coating resisted . These shelters proved effective in reducing fatalities during , as the earthen cover dispersed shock waves and fragments, contributing to Britain's relatively low civilian bombing casualties of around 50,000 despite intense raids. However, they had notable limitations: prone to flooding in wet conditions, uncomfortably cold and damp in winter, and often underutilized in urban settings due to space constraints—only about 27% of households employed them regularly. Some shelters endured post-war, remaining structurally sound after over 70 years due to their robust design. In addition to Anderson models, private garden shelters occasionally incorporated brick or concrete elements where metal was scarce, though these were rarer owing to wartime material rationing prioritizing communal or military needs. Comparable outdoor designs appeared elsewhere, such as sturdier in , which offered potentially superior protection but saw limited adoption outside specific contexts.

Communal and Public Structures

Communal and public air raid shelters encompass large-scale structures designed to protect groups of civilians in urban settings, often featuring construction, multiple entry points, and amenities for extended occupancy. During , these included deep-level shelters excavated beneath stations, dug by hand to depths of 30 meters and lengths exceeding 400 meters each. Eight such shelters—at , , , Goodge Street, , Clapham North, , and Clapham South—were completed by 1942, each with a capacity of 8,000 people across upper and lower levels equipped with three-tier bunks, eight canteens, lavatory blocks, and medical bays. Initially repurposed for military storage from 1942 to 1943, five opened to the public in July 1944 to counter V-1 and threats, providing shelter for 40,000 individuals amid intensified attacks. In , Hochbunker represented above-ground communal variants, built as multi-story towers to house hundreds during bombings. The Pragsattel Hochbunker in , constructed from 1941 to 1942, accommodated up to 1,000 people with basic protective features against blast and fragmentation. Similarly, the Trier Hochbunker, erected adjacent to the town hall between 1941 and 1943, stood 38 meters tall to shield officials and residents, though incomplete at war's end. These structures prioritized rapid construction using local labor and materials, often integrating ventilation systems to sustain air quality for short-term communal use. Post-World War II, Switzerland established the world's most comprehensive public shelter network during the , mandating coverage for every resident via a 1963 law that resulted in over 370,000 bunkers by the 1970s, sufficient for its then-6.4 million population. Facilities like the Sonnenberg complex near were engineered for 20,000 occupants, featuring autonomous power, water filtration, and medical provisions for prolonged nuclear scenarios. As of 2024, ongoing upgrades address aging infrastructure, with examples such as Zurich's Urania garage-bunker retrofitted for 11,000 people, reflecting heightened geopolitical tensions. Finland maintains 50,500 operational shelters—public and communal—capable of protecting its 5.5 million citizens, compliant with standards requiring ventilators, blast doors, stackable bunks, and since updated in 2000. In , public shelters mandated since 1951 supplement building-integrated units, ensuring access for 65% of the population through community-based reinforced rooms and standalone bunkers tested against rocket barrages. These modern public structures emphasize rapid access, often within 90 seconds of alerts, and integrate with protocols for efficacy.

Underground and Tunnel-Based Shelters

Underground shelters, constructed specifically below ground level, provided superior protection against aerial bombardment by leveraging soil overburden to absorb shockwaves and resist bomb penetration, with depths typically exceeding 20 meters to mitigate direct hits from conventional high-explosive ordnance. In Britain during , the most extensive system comprised eight deep-level shelters built beneath stations between 1940 and 1944, each featuring two parallel cylindrical tunnels approximately 400 meters long and 5 meters in diameter, capable of housing up to 8,000 people with basic bunks, medical facilities, and chemical toilets. These structures, excavated in clay at depths around 30 meters, were initially reserved for government use but opened to civilians amid intensified raids, sheltering thousands during despite challenges like and outbreaks from . ![Belsize Park deep level shelter][float-right] Tunnel-based shelters often repurposed pre-existing subterranean infrastructure, such as mining tunnels or urban rail systems, to expedite civilian protection without new excavations; their linear design facilitated rapid evacuation but exposed vulnerabilities to longitudinal blast propagation and ventilation failures. In , , chalk cliff tunnels dating to the were expanded in to accommodate over 4,000 people, featuring reinforced entrances and electric lighting to endure sustained bombing. German cities similarly adapted U-Bahn networks, where stations and tunnels served as primary refuges during Allied air campaigns from 1943 onward, holding up to 1,300 individuals per site for short durations with minimal amenities, though poor air circulation led to documented cases of asphyxiation risks during prolonged alerts. In contemporary conflicts, deep urban tunnels continue to demonstrate efficacy against precision-guided munitions and drones, as evidenced by Kyiv's Soviet-era metro system during the 2022 Russian invasion, where stations over 50 meters deep—such as Arsenalna at 105 meters—shielded hundreds of thousands from missile strikes, maintaining habitability through platform-level sleeping arrangements and supplies despite power disruptions. Empirical data from the conflict indicates these facilities reduced direct blast casualties by dispersing populations underground, though secondary hazards like flooding from damaged necessitated engineering retrofits for long-term use. Overall, both purpose-built underground complexes and adapted tunnels prioritize blast attenuation via depth and mass, but require robust sealing against and toxic fumes, with historical records showing survival rates exceeding 95% for occupants not exposed to structural breaches.

Efficacy, Limitations, and Criticisms

Empirical Performance in Historical Conflicts

In the (1936–1939), constructed over 1,300 underground air raid shelters to protect civilians from systematic bombings by Italian and German aircraft supporting Nationalist forces, with these structures credited by local authorities for saving thousands of lives during raids that targeted the city as the first instance of deliberate civilian aerial bombardment in . The shelters, often built in metro stations, schools, and basements, accommodated up to 400,000 people at peak usage and mitigated casualties from high-explosive and incendiary bombs, though exact mortality reduction figures remain undocumented due to wartime chaos and Franco-era suppression of Republican records. During the and (July 1940–May 1941), British air raid shelters, particularly the 3.6 million Anderson shelters distributed free to lower-income households, proved effective against blast and shrapnel when properly installed half-buried in gardens with earth cover, as evidenced by instances like the raid where shelters endured while surrounding homes were obliterated, protecting occupants from structural collapse. Indoor Morrison shelters similarly shielded against falling debris in damaged buildings, contributing to overall civilian air raid deaths totaling 60,595 across the —far below pre-war government estimates of up to 600,000 in the first weeks alone—though low adoption rates limited impact, with only 27% of Londoners using private shelters during early raids. Public deep shelters and Tube stations housed crowds but faced risks, as in the disaster on March 3, 1943, where 173 died in a panic-induced crush unrelated to direct bombing. In , extensive networks of Hochbunkers and underground shelters, including Berlin's Flak Towers accommodating up to 10,000 each, provided robust protection against Allied from 1942–1945, reducing immediate blast fatalities in cities like during the July 1943 Operation Gomorrah , where shelters initially saved lives from explosive impacts but failed against suffocation and heat in prolonged infernos, contributing to 40,000 total deaths. Overall German civilian casualties reached 305,000 killed and 780,000 wounded despite sheltering 20 million from utilities loss, with post-war surveys indicating shelters mitigated higher potential losses from conventional ordnance but were overwhelmed by area bombing tactics emphasizing incendiaries over precision strikes. Empirical assessments from the estimated that without shelters, urban mortality rates could have doubled in heavily raided areas, underscoring their role in causal chains of survival through fragmentation resistance and overhead cover, though direct hits remained lethal regardless of design.

Engineering and Practical Shortcomings

Many air raid shelters, particularly those constructed during , were engineered primarily to mitigate blast effects and shrapnel from near misses rather than direct bomb impacts, rendering them vulnerable to high-explosive penetrators like the British Tallboy or German V-2 rockets, which could collapse even structures. Surface-level communal shelters in Britain, built hastily from brick and under the 1939 Civil Defence Act to hold up to 50 people each, frequently suffered from substandard mortar and rushed assembly, leading to partial or total collapses under lateral blast pressures exceeding design tolerances of approximately 1-2 psi. Corrugated steel Anderson shelters, distributed free to over 2.25 million low-income British households by 1940, demonstrated against overhead soil burial but exhibited critical weaknesses in doorways, which relied on improvised wooden frames prone to under or blast waves, and overall thin 14-gauge (2 mm) panels susceptible to and deformation over time. Underground or semi-sunken designs, such as adapted tube stations, faced structural risks from bomb-induced flooding; for instance, a direct hit at on October 14, 1940, flooded tunnels via ruptured water mains, drowning 64 occupants despite watertight doors that instead trapped victims. Similarly, a January 11, 1941, strike at Bank station killed 53 due to ceiling collapse and flooding from severed infrastructure. Practical habitability was compromised by inadequate ventilation systems, which in enclosed spaces like tunnels or buried shelters allowed rapid accumulation and oxygen depletion during prolonged occupancy, exacerbating risks of asphyxiation or outbreaks in unsanitary conditions without proper . Anderson and similar outdoor models in low-lying areas routinely flooded from or rainfall, rendering interiors uninhabitable and promoting mold growth, while poor failed to counter sub-zero temperatures, with occupants reporting risks during winter blackouts. Access delays during short-warning raids—often under 15 minutes—compounded these issues, as narrow, blast-deflecting entrances clogged with soil or panic-driven crowds, limiting effective evacuation to seconds rather than the minutes required for safe ingress.

Psychological and Societal Impacts

During from September 1940 to May 1941, air raid shelters provided civilians with a perceived sense of security that helped maintain despite intense bombing, as empirical surveys post-raids showed limited widespread psychological breakdown, with psychiatric casualties remaining low relative to the scale of attacks—fewer than 3,000 cases of "bomb " reported in despite over 40,000 civilian deaths nationwide. However, confinement in overcrowded public shelters, such as Underground stations housing up to 177,000 people nightly, often exacerbated anxiety through poor ventilation, , and fear of gas or crush , leading to isolated incidents of and somatic complaints like fainting or . Deep-level shelters were initially resisted due to concerns over mass akin to theater crowd crushes, though usage ultimately correlated with lower acute stress when bombs struck nearby, as occupants reported reducing dread. Societally, shelters fostered cross-class interactions and mutual aid, as civilians collectively constructed and shared facilities like Anderson shelters—over 2.5 million distributed by 1941—breaking down pre-war social barriers and contributing to post-war welfare reforms by highlighting vulnerabilities in urban poor housing. Yet, they disrupted daily routines, with frequent alerts interrupting sleep and work, elevating fatigue and family tensions; women, often managing home shelters, faced heightened burdens, while child evacuations from shelter-dependent areas strained community bonds. Long-term, exposure to raids even with shelter protection linked to elevated adult mental health issues in affected cohorts, including 10-15% higher rates of depression and anxiety decades later, per cohort studies of German and British wartime children. In modern conflicts, such as Israel's rocket alerts since 2000, mandatory shelters mitigate immediate fatalities—reducing casualties by up to 90% in protected areas—but repeated interruptions foster , with studies showing 20-30% of frequent users developing PTSD symptoms from anticipatory anxiety rather than direct hits. Similarly, in Ukraine's 2022 invasion, Kyiv's metro stations repurposed as shelters for over 100,000 nightly sheltered populations experienced heightened anxiety from siren-induced disruptions, correlating with increased somatic symptoms and sleep disorders in 40% of users per field surveys, though communal aspects provided temporary social cohesion. These patterns underscore shelters' dual role: buffering physical peril while amplifying psychological strain from uncertainty and isolation, with children in such environments facing amplified risks of developmental trauma.

Modern and Contemporary Applications

European Contexts

In , following the Russian invasion on February 24, 2022, Soviet-era underground shelters and have been extensively utilized as air raid protections against and drone strikes. In , 46 metro stations function as bomb shelters, accommodating over 40,000 people in the initial months of the conflict, with stations providing refuge during frequent air raids. Issues such as locked or inaccessible shelters have persisted, contributing to civilian casualties, as evidenced by three deaths in in June 2023 after being denied entry to a shelter during a . By October 2025, Ukrainian authorities planned to deploy approximately 500 mobile bomb shelters to address gaps in coverage, particularly in areas lacking permanent structures. Nordic and Alpine countries maintain robust networks originally developed during the , adapted for contemporary threats including potential Russian aggression. operates 50,500 civil defense shelters with capacity for 4.8 million individuals, covering about 85% of its 5.6 million population; 91% of these structures can withstand conventional bombs and missiles, with many dual-purposed as public facilities like swimming pools and amusement parks. possesses 64,000 air-raid shelters protecting roughly 70% of its populace, built over eight decades for wartime contingencies. leads with over 370,000 bunkers capable of sheltering 114% of its population against nuclear and conventional attacks, a policy enforced since the requiring shelters in new constructions. Amid heightened tensions from Russia's war in , several European nations have initiated expansions of shelter infrastructure. , with only 579 public shelters for 480,000 people as of 2024, announced plans in June 2025 to rapidly augment its network in response to perceived Russian threats, including revamping tunnels and metro systems. Private construction has surged, rising 200% in since early 2022 and booming in , driven by civilian demand for personal fortifications. These developments reflect a pragmatic reassessment of civil protection needs, prioritizing empirical resilience over prior assumptions of diminished risks.

Middle Eastern and Ongoing Conflicts

In Israel, civilian protection against rocket and missile attacks from Gaza-based groups like and Lebanon-based relies on a network of reinforced safe rooms (known as mamadim) in residential buildings constructed after 1991, as mandated by the Law amendments following the 1991 Scud attacks. Public bomb shelters (miklatim) and underground facilities supplement these, with over 13,000 public shelters nationwide accommodating short-notice evacuations during barrages. Between 2005 and 2014, militants fired more than 16,500 rockets into , yet civilian fatalities remained low—fewer than 30—due to rapid shelter access (typically under 90 seconds via sirens) combined with interception systems like , which has a success rate exceeding 90% against short-range threats. During the October 2023 attack and subsequent escalations, including Iran's June 2025 missile barrages, shelters prevented mass casualties; for instance, in a building struck in 2025, 180 occupants in a shelter emerged unharmed. However, disparities persist, with Arab-majority localities showing 20-30% lower coverage of protective structures compared to Jewish areas, exacerbating vulnerabilities in mixed-threat zones. ![Flickr_-Israel_Defense_Forces-_Israelis_Hiding_in_a_Bomb_Shelter.jpg][float-right] In Gaza, has constructed an extensive tunnel network estimated at 500-700 kilometers for military purposes, including fighter protection and weapon storage, but has not built equivalent shelters despite ample resources diverted from . officials have stated that tunnels serve to shield combatants from airstrikes, while safety falls to international agencies, explicitly rejecting population-wide shelters to maintain a strategy of embedding operations in urban areas, which increases risks during Israeli responses. This approach, documented in communications and independent analyses, prioritizes propaganda gains from high exposure over protective measures, with no verified large-scale bunkers despite repeated conflicts since 2007. In Syria's and 's Houthi conflict, air raid shelter usage is minimal and , with often relying on basements or UN-provided temporary covers amid urban airstrikes, contributing to elevated deaths—over 10,000 in since 2015—due to absent systematic . In ongoing conflicts like Russia's 2022 invasion of , subway systems in cities such as have served as primary air raid shelters, leveraging Soviet-era designs with stations buried 30-100 meters deep to withstand blasts. By mid-2023, 46 stations operated 24/7 as bunkers equipped with ventilation, , and for thousands during nightly drone and alerts, housing residents long-term amid power outages. Ukrainian authorities have deployed over 500 mobile shelters by October 2025, but metro reliance persists, with incidents like the July 2025 strike on Lukyanivska station highlighting vulnerabilities despite reinforcements. ![People_on_a_metro_station_during_Russian_invasion%252C_Kyiv%252C_2022.jpg][center]

Asian Preparations and Usage

maintains approximately 19,000 bomb shelters nationwide, with over 3,200 located in , primarily designed to withstand conventional attacks rather than nuclear or chemical threats from . These facilities, often integrated into , parking garages, and malls, have been mapped on smartphones since July 2023 to facilitate public access during alerts. Despite frequent missile tests prompting shelter warnings, many remain underutilized by civilians, who view them as outdated or insufficient against barrages from across the . In response to escalating nuclear risks, announced plans in October 2025 for its first dedicated civilian nuclear bunker beneath a complex, spanning 2,147 square meters and accommodating 1,020 people for up to 14 days with air filtration, power, and water systems. Japan has historically lacked widespread air raid infrastructure, with civil defense emphasizing evacuation over hardened shelters, leaving populations vulnerable to North Korean missile overflights that have triggered shelter alerts since 2017. Recent policy shifts, driven by the 2022 Strategy, include doubling shelter capacity and initiating a program to protect 10 million people through underground facilities under the Civil Protection Law, designed for brief stays of 1-2 hours during sporadic attacks. Implementation faces challenges, including local surveys for suitable sites and debates over space allocation (at least 2 square meters per person with basic utilities), amid public calls for more robust defenses against ballistic threats. Taiwan conducts annual air raid drills simulating Chinese missile and invasion scenarios, such as the July 17, 2025, exercise in where sirens halted traffic and directed residents to shelters, though many facilities were found locked or inaccessible, highlighting gaps in readiness. efforts, rooted in Japanese-era practices but revived post-2010s due to Beijing's military buildup, include urban warfare rehearsals and mobile alerts, yet actual shelter usage remains limited outside drills, with emphasis on rapid dispersal over prolonged stays. In , border tensions with prompted nationwide drills in May 2025, testing air raid sirens, blackouts, and shelter protocols not practiced at scale since the 1971 war, with evacuations simulated for schools and hospitals. The government has constructed thousands of "Modi Bunkers"—community shelters in vulnerable districts like , , Poonch, and —equipped for short-term protection against cross-border strikes, though their efficacy depends on maintenance and public awareness amid sporadic escalations.

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