This chapter gives a brief overview of the global application of air power at the strategic and operational levels of war, covering the period from the First World War to the current engagements in Iraq. He shows how air power emerged as a strategic element during the course of the Second World War, made dominant contributions in a series of wars and campaigns during the Cold War period, and has come of age in the second aerospace century. Commanders from all services, including those on the home front, learned quickly that control of the air had to be fought for and maintained, often at considerable cost. During the 1990s and 2000s Western nations sought to replicate the military success of Operation Desert Storm, but found themselves facing two separate realities: air power as the supported force in inter-state conventional conflicts and as the supporting instrument in a series of intra-state counter-insurgency campaigns. The history of air power over the last century-plus is a story of evolving military effectiveness in all of its major roles, adapting to ever-changing political circumstances. In the end, throughout all the history of air power, ‘control of the air is the one role to rule them all’.