London was bombed heavily in World War 2 as part of a series of attacks that became known as "The Blitz", lasting from 1940 into 1941. In preparation for air or land attacks, England put into place evacuation plans that moved children from London, a major target, into host homes in the countryside, as in the case of the Pevensie children. However, the lack of any attack or invasion throughout 1939 and early 1940 led many to believe the evacuation plans were unnecessary, and parents started bringing their children home. Then came the Blitz.
Attacks happened primarily at night, though there were daytime raids as well. Although many would take shelter in the underground subway (known as the Tube) or in shelters they constructed in their backyards, there was not enough shelters for everyone. Many took advantage of ongoing evacuation schemes. Some moved outside London and commuted back into the city for work and school. Those who had friends or relatives living in the countryside moved in with them, or if unable to leave London sent their children to live with them.