Strategic bombing during World War I (28 July 1914 – 11 November 1918) was principally carried out by the United Kingdom and France for the Entente Powers and Germany for the Central Powers. Most of the belligerents of World War I eventually engaged in some form of strategic bombing. The aerial bombing of cities, intended to destroy the enemy's morale, was introduced by the Germans in the opening days of the war. A multi-national air force to strike at Germany was planned but never materialized.
Early strategic bombing attempts led to the development of specialized bomber aircraft, during World War I. Initially bombs were dropped by hand and aimed by the naked eye, but by the end of the war bombsights had been developed. The introduction of air raid warnings and shelters can be dated to World War I, as can the design of anti-aircraft artillery and the development of methods for coordinated aerial defence. Many of the advocates of strategic bombing during the interwar period, such as Italy's Giulio Douhet, America's Billy Mitchell, and Britain's Hugh Trenchard, had commanded aircraft during World War I. The improvements in aircraft technology during and after the war convinced many that "the bomber will always get through", and this belief influenced planning for strategic bombing during World War II.