Portal was Chief of the Air Staff from 1940-45 and as such directed the policy and operations of the RAF. He was also a key figure in Anglo-American strategic planning and attended the major inter-Allied war conferences. As an advocate of area bombing he was initially in conflict with the United States policy of daylight precision bombing. A compromise, in the form of the Combined Bomber Offensive, was reached at the Casablanca Conference in January 1943. In early 1944 Portal and ‘Bomber’ Harris clashed when Portal revised his views on strategic bombing, concluding that air power should be a component of the Allied campaign in Europe, rather than a war-winning strategy in its own right.