Strategic bombing during World War II was the sustained aerial attack on railways, harbours, cities, workers' and civilian housing, and industrial districts in enemy territory during World War II. Strategic bombing is a military strategy which is distinct from both close air support of ground forces and tactical air power. During World War II, it was believed by many military strategists of air power that major victories could be won by attacking industrial and political infrastructure, rather than purely military targets. Strategic bombing often involved bombing areas inhabited by civilians and some campaigns were deliberately designed to target civilian populations in order to terrorize them and disrupt their usual activities. International law at the outset of World War II did not specifically forbid aerial bombardment of cities despite the prior occurrence of such bombing during World War I, the Spanish Civil War, and the Second Sino-Japanese War.
Strategic bombing during World War II began on 1 September 1939 when Germany invaded Poland and the Luftwaffe began bombing cities and the civilian population in Poland in an aerial bombardment campaign.