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.
Germany
The first strategic bombing in history was also the first instance of bombs being dropped on a city from the air. On 6 August 1914 a German Zeppelin bombed the Belgian city of Liège. Within the first month of the war, Germany had formed the "Ostend Carrier Pigeon Detachment", actually an airplane unit to be used for the bombing of English port cities. During the First Battle of the Marne, a German pilot flying aerial reconnaissance missions over Paris in a Taube regularly dropped bombs on the city. The first raid dropped five small bombs and a note demanding the immediate surrender of Paris and the French nation. Before the stabilisation of the Western Front, the German aircraft dropped fifty bombs on Paris, slightly damaging Notre Dame Cathedral.
The first extended campaigns of strategic bombing were carried out against England by the German Empire's fleet of airships, which were then the only aircraft capable of such sustained activities so far from their bases. This campaign was approved on 7 January 1915 by Kaiser Wilhelm II, who forbade attacks on London, fearing that his relatives in the British royal family might be injured. These restrictions were lifted in May, after British attacks on German cities. The first attacks on England were on 19 January, and struck the Yarmouth area and King's Lynn. In Britain, fear of the Zeppelin as a weapon of war preceded its actual use: even before the war the British public was gripped by "zeppelinitis".
The Zeppelin proved too costly compared to airplanes, too large and slow a target, its hydrogen gas too flammable, and too susceptible to bad weather, anti-aircraft fire (below 5,000 feet) and interceptors armed with incendiary bullets (up to 10,000 feet) for the Imperial German Army (Reichsheer), which abandoned its use in 1916. The Imperial German Navy (Kaiserliche Marine), whose airships were primarily used for reconnaissance over the North Sea, continued to bomb the United Kingdom until 1918. In all, fifty-one raids on Great Britain were carried out, the last by the Navy in May 1918. The most intense year of the airship bombing of England was 1916. In December 1916, two Zeppelins of the R Class took off from Wainoden in an attempt to bomb Saint Petersburg. One was forced down by adverse weather conditions and damaged beyond repair, while the other, hampered by engine problems, turned back before it reached the target. No further attempt to bomb Saint Petersburg was made. Germany employed 125 airships during the war, losing more than half and sustaining a 40% attrition rate of their crews, the highest of any German service branch.