Strategic bombing first occurred during World War I when belligerents on both sides used rigid airships and heavy aircraft to deliver bombs on enemy targets far behind the front lines. Given the technology of the time, air strikes were few in number, inaccurate, and had a minor military impact. The psychological impact, however, was disproportionately large. The reaction of the public and workforce was immediate, as evidenced by factory absentee rates, the numbers of people fleeing cities for the countryside, and the clamor for government action. This strong reaction was caused by the novelty of the air weapon, not by its accuracy or destructiveness.
This belief in the psychological effects of strategic bombing strongly affected the public, governments, and military leaders during the interwar period. The three leading air theorists of this era—Giulio Douhet (Italy),Hugh Trenchard (Britain), and William “Billy” Mitchell (United States)—all assumed such a psychological impact in their projections of future war. The irony of this belief was its implicit promise that the horrors of strategic bombing would be so great that resorting to war would be less likely. In short, early air theorists saw strategic bombing as a deterrent that would keep the peace.
If deterrence failed, however, airmen hoped that strategic bombing would offer an antidote to the trench-warfare carnage of World War I. Strategic bombing, so the argument went, could bypass the tactical battle and strike directly at the “vital centers” of an enemy country. Strategic bombing, in conjunction with surface operations, would quickly bring victory. The intended targets of the bomber offensive were the industrial, economic, transportation, and government centers of the enemy. Note that it was the objective that determined whether a target was strategic or tactical, not the aircraft or weapon being used. Douhet—but not Trenchard and Mitchell—also called for direct attack on the population in the belief that their morale would break and they would demand an end to the war.
Strategic bombing during World War II was the sustained aerial attack on railways, harbors, cities, workers' 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 sometimes bombing campaigns were deliberately designed to target civilian populations in order to terrorize, disorganize, 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 (German air force) began bombing cities and the civilian population in Poland in an indiscriminate aerial bombardment campaign. As the war continued to expand, bombing by both the Axis and the Allies increased significantly. The RAF flew its first strategic bombing raid on Germany at Mönchengladbach on 11 May 1940 and in September 1940, the Luftwaffe began targeting British cities in 'The Blitz'. From 1942 onward, the British bombing campaign against Germany became less restrictive and increasingly targeted industrial sites and eventually, civilian areas. When the United States began flying bombing missions against Germany, it reinforced these efforts and controversial firebombings were carried out against Hamburg (1943), Dresden (1945), and other German cities.
In the Pacific War, the Japanese bombed civilian populations throughout the war (e.g. in Chongqing). The U.S. strategic bombing of the Japanese Empire began in earnest in October 1944 and escalated into widespread firebombing, which culminated in the atomic bombings of Hiroshima and Nagasaki on 6 and 9 August 1945 respectively, and the Japanese surrender on 15 August.
The effect of strategic bombing was highly debated during and after the war. Both the Luftwaffe and RAF failed to deliver a knockout blow by destroying enemy morale. However some argued that strategic bombing of military targets could significantly reduce enemy industrial capacity and production and in the opinion of its interwar period proponents, the surrender of Japan vindicated strategic bombing.