Air raid shelters are structures for the protection of the civil population as well as military personnel against enemy attacks from the air.
The characteristics of the structures serving as air raid shelters in World War Two
Air raid shelters were built specifically to serve as protection against enemy air raids. However, pre-existing edifices designed for other functions, such as underground stations (tube or subway stations), tunnels, or cellars in houses, basements in larger establishments, and railway arches , were also utilised. These structures, being below ground or almost so, and being especially strengthened to support the weight of the buildings above them, were therefore particularly suitable to safeguard people during air raids.
Cellars in Continental Europe have always been much more important than they have in the United Kingdom, and especially in Germany almost all houses and apartment blocks have been and are still being built with cellars. For this reason, air-raid precautions during World War II in Germany could be much more readily organised by the authorities than it was possible to do so 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; access to the cellars was safe in the event of an air raid; once inside, the occupants were secure for any incidents other than direct hits during the air raid; and that the means of escape in case of a real emergency were easily available.
It should nevertheless be emphasized that the inadequacies of the cellars and basements became only too apparent in the so-called firestorms during the incendiary attacks on the larger German inner cities, especially those of Hamburg and Dresden.
When burning buildings and apartment blocks above them collapsed in the raging winds (that could reach well over 800° C), the occupants often became trapped in these basement shelters that had become overcrowded after arrivals of inhabitants from other buildings rendered unsafe through earlier attacks.
It was then that of the occupants who died, between 60 and 80 per cent perished from heat-stroke or carbon monoxide poisoning, rather than by the fire itself.
Cellars in the UK
Cellars in the UK, however, 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 for reasons of avoiding the higher costs the building of cellars entailed. Since house building had increased vastly between the wars, the lack of cellars in these recent housing developments was to become 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 air raids were being contemplated by Germany as a means of demoralising the population and disrupting supply lines in Britain.
First recommendations included that members of the household should remain in the so-called under-the-stairs space, the triangular spandrel section between the string of the stairs and the wall, during the air raid.
Later, materials were being supplied to householders by the authorities, to construct street communal shelters and so-called Morrison and Anderson shelters.
Basements, the storeys beneath the larger kinds of premises and establishments, also became available for the use of air raid shelters. In this way, basements under factory premises, schools, hospitals, department stores and other businesses were utilised. What had to be kept in mind, however, was that heavy machinery and materials, water storage facilities above the shelter, and insufficient support structures, such as pillars and beams beneath the shelter ceiling, did not aggravate the situation and endanger the lives of the occupants in the basements further.
When Wilkinson’s Lemonade factory in North Shields, Tyneside, received a direct hit on Saturday, 3rd May 1941 during a German attack on the north-east coast of England, 203 occupants lost their lives when the ceiling of the basement in which they were sheltering, and the heavy machinery above it, collapsed.
Railway arches and subways (underpasses)
Railway arches and subways, too, were being utilised in the UK for air raid protection at all times during World War II.
Railway arches were deep, curved structures of brick or concrete, set into the vertical sidewalls of railway lines, that 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 60 to 150 or so persons. 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 (so-called in British usage to denote underpasses) were actual thoroughfares also in the shape of arches, normally allowing passage underneath railway lines.
Underground (tube) stations
At the beginning of the war, the Minister of Home Security, Herbert Morrison, had misgivings about the utilisation of the tube stations and underground tunnels as public shelters. The reasons he gave were his concern about the spread of disease due to the lack of toilet facilities at many stations, the inherent danger of people falling on to 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.
However, it was soon evident that these fears were groundless. People were keen to get on with their lives as normally as possible whatever hardships they encountered outside the tube shelters. Nevertheless, Londoners preferred to use the Underground stations to any other shelters because they felt safest there, and they were willing to demonstrate their determination that they should be allowed to use the tube stations and tunnels.
The government soon realised the extent of this determination, and that the Underground, after all, could be the answer to the problem of the lack of available shelters and cellars in the town. On 21st September 1940 the Aldwych branch of the Piccadilly Line was closed to trains, tracks were concreted over, and reinforced floodgates were installed that could be closed instantly in case of burst river embankments due to bomb damage. 79 stations were fitted with bunks for 22,000 people, supplied with first aid facilities and had chemical toilets put in. 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.
Factories too were given permission to use the Underground stations, government offices were installed in some others and the anti-aircraft centre for London was able to utilise one station as its headquarters.
However, tube stations and tunnels were still vulnerable to direct hits when a bomb might explode immediately above a particular stretch of the system, and several such incidents did in fact occur.
On 17th September 1940, at Marble Arch station, 20 people were killed.
On 14th October 1940, a bomb penetrated the road and tunnel at Balham station, blew up the water mains and sewage pipes, and killed 68 people.
At Bank station a direct hit caused a crater of 120ft by 100ft on 11th January 1941, the road above the station collapsed and killed 56 occupants.
However, the highest death toll was caused during an accident at Bethnal Green tube station on March 8th 1943, when 1,500 people were rushing down the stairs to the shelter during a particularly severe air raid. Someone stumbled, and the crowd pushing on, were falling on top of one another. 173 people were crushed to death in the disaster.
The extent of the disasters and the number of people killed was not disclosed until after the war.
Nevertheless, the London Underground system during the war 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 World War II. Although not a great number in comparison to the total number of the inhabitants of the capital, it almost certainly saved many lives of the people who probably would have had to find alternative, less secure means of protection.
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 coalmining.
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. 12m deep in places, the tunnels, stretching in parts beneath the city of Newcastle, were converted to air raid shelters with a capacity for 9,000 people.
The large 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 World Wars I and II, until it was capable of accommodating large parts of the secret defence systems protecting the British Isles. On 26th May 1940 it became the headquarters under Vice Admiral Bertram Ramsay of “Operation Dynamo”, from where the rescue and evacuation of up to 338,000 troops from France was directed.
Street communal shelter
In the United Kingdom, it was being recognized early that public shelters in open spaces, especially near streets, were urgently needed for pedestrians and 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 14-in brick walls and one-foot thick 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.
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 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. It was then that these shelters began to become 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.
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. After evaluation by Dr David Anderson, Bertram Lawrence Hurst, and Sir Henry Jupp, of the Institute 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 6ft (1.8m) high, 4ft 6in (1.4m) wide, and 6ft 6in (2m) long. They were buried 4ft (1.2m) deep in the soil and then covered with a minimum of 15in (0.4m) of soil above the roof. 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 was wide variations in comfort.
Anderson shelters were issued free to all householders who earned less than £250 a year, and those with a higher income were charged £7. 150,000 shelters of this type were distributed from February 1939 to the outbreak of war. During the war a further 2.1 million were erected.
Morrison shelters, officially termed Table (Morrison) Indoor Shelters, were 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 6 ft 6in (2m) long, 4ft (1.2m) wide and 2ft 6in (0.75m) high, had a solid 1/8in steel plate “table” top, welded wire mesh sides, and a metal lath “mattress”- type floor. Altogether it had 359 parts and had 3 tools supplied with the pack. Structurally it was designed to absorb the impact of debris falling on the top of the shelter. The sides could be removed to permit it being used as a table.
500,000 Morrisons 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 (doodlebug) attacks.
In one examination of 44 severely damaged houses where 136 people had occupied Morrison shelters, and three had been killed, 13 seriously injured, and 16 slightly injured. The fatalities, it was found, occurred in a house which had a direct hit, and some of the severely injured were in shelters sited incorrectly within the houses.
Military citadels under London
See the article Military citadels under London for information on other structures built to withstand air raids.
Hochbunker(s), or "high-rise" bunkers or (blockhouses), were a peculiarly German type of construction, designed to relieve the pressure 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 any other shelters these buildings were indeed considered completely bomb-proof. They also had the advantage of being built upward - much more cheaply - than downward by excavation. There were no equivalents of hochbunkers in the cities of the Allies countries.
Hochbunkers consisted usually of large concrete blocks above ground of thicknesses between 1m and 1,50m, huge lintels above doorways and openings, and they often had a constant interior temperature of 7 to 10° C., thus being perfectly suitable for laboratory utilization during and after the war. They had been designated to protect people, administrative centres, important archives and works of art.
Their structures took many forms, square blocks, but also lower and longer rectangular shapes, straight towers of a square plan rising to great heights, as well as 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 to this day. They have been converted into offices, storage space, and some have even been adopted for hotels, hospitals and schools, as well as many other peacetime purposes. 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, hochbunkers which during the war had anti-aircraft batteries at their top platforms. Only a crack could be achieved in one of the walls, before the attempt had to be abandoned. The Pallasstrasse air-raid shelter, Schöneberg has a post-war block of flats built over the shelter. During the Cold War the shelter was in use as a NATO food-store.
Brick-built shelters with reinforced concrete roofs were often constructed in backyards and gardens in the UK. An author of this article still had this type of shelter at the back of his house, a 12-inch thick solid reinforced concrete plate 8ft by 6ft resting on four brick walls plus door surrounding the shelter. The rear wall of the shelter was entirely embedded in the steeply rising hill garden, the two side walls were half-covered by the scarp and only the front was wholly free-standing.
Military air raid shelters included blast pens at airfields for the security of aircrews and aircraft maintenance personnel away from the main airbase buildings.
It should be noted, however, that few shelters could have been considered ultimately safe in a case of a direct bomb-hit. Nevertheless, German authorities laid claim to höchbunkers being totally bomb-proof. But none were hit with any of the 41 Grand Slam bunker busters dropped by the RAF during World War II. Two were dropped on the U-Bootbunkerwerft Valentin submarine pens near Bremen, they penetrated 4 to 7 meters of reinforced concrete, bringing the roof down.