This thesis charts the development of area bombing in British theory and practice before its formal adoption in the Second World War, and seeks to discover where its earliest origins can be located. Area bombing was the official policy of Royal Air Force Bomber Command between 1942 and 1945 in its strategic air offensive against Germany, and involved the bombing of industrial cities with the purpose of breaking down civilian morale and disrupting the German war economy. Most historical accounts present area bombing as a gradual development in bombing policy during 1940 and 1941, forced by a lack of success in destroying precise industrial targets from the air. This was the Air Force’s stated policy during the previous two decades, but it proved impossible to implement under wartime conditions. Area bombing was thus gradually adopted by progressively broadening the definition of targets from individual installations to entire towns and cities. This thesis rejects the traditional view, arguing instead that area bombing was at the heart of British bombing policy as early as the First World War. The legacy of this saw an ‘area bombing mentality’ cemented in the strategy of the Royal Air Force during the interwar period. As it was not possible to openly advocate the bombing of civilians during the 1920s and 1930s, this was shrouded in ambiguous language and kept hidden. However, the roots of area bombing come to the surface several times between the wars, and the speed with which area bombing was adopted in 1940 and 1941 shows that they were never deeply buried. While many historians have uncovered individual details that collectively support this contention, none have traced the development of this thought across the period 1917-42. Using a selection of contemporary documents and a thorough review of the secondary literature, this work shows that far from being an improvisation forced by necessity, the adoption of area bombing was unsurprising and can be traced back to 1917.