The first of 2 1⁄2 million Anderson air raid shelters appeared in North London.
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).Before WWII, the U.K. had difficulty choosing the location of air raid shelters. During WWII, many types of structures were used as air raid shelters such as cellars, German Hochbunkers, basements, and underpasses. Bombing raids during WWI led the U.K. to build 80 specially adapted underground tube stations as shelters, later abandoning them as viable options for citizens during air attacks. Londoners ignored the government and flooded into underground stations during 1940 bombing attacks. Bombs and accidents took civilian casualties at the underground stations.
The U.K. 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 also in common use in the U.K. Indoor shelters known as Morrison shelters were also in use.
Air raid shelters are still in use to some extent in various nations such as Spain, Switzerland, Israel, Singapore and Taiwan.