One of the world's best military historians tells the story of air power, its remarkable dominance as an instrument of war throughout the second half of the twentieth century, and now argues provocatively that it is obsolete, despite the billions of dollars we spend. There are many myths about air power, among them the claims so often made about technological progress making modern air power more effective than it used to be. It is not true that precision guided munitions have made fighter bombers more effective against mobile targets in particular than their predecessors in World War II; the so-called Revolution in Military Affairs notwithstanding, US ground troops calling for air support in Iraq in 2003 did not receive it any faster than Allied forces did in Tunisia in 1943 or in France in 1944-45. If air power is so important, why is it that the number of military aircraft being procured around the world each year has fallen from over 200,000 in 1944 to a few hundred today? If the idea of air war is anything more than a notion, where is it likely to happen? Many kinds of military aircraft can be, indeed are being, replaced by other systems such as helicopters, ballistic missiles, cruise missiles, and unmanned airborne vehicles (UAVs). Often there is no very good reason why those systems should be operated by an independent air force and not by some other kind of organisation. There is the relentless spread of forms of war such as terrorism, guerrilla and insurgency in which aircraft have always been much less useful than in conventional warfare. In these wars, so vast is the disproportion between the cost of military aircraft and what they can actually achieve that it can only be described as preposterous. Martin Van Creveld shows that air forces are an institutional relic; their glorious history has not prepared them for a future. As he has been writing the book, Van Creveld has given a lecture outlining the thesis to military around the world. It has led both to applause and near violence in the reaction of the audiences. The book will provoke a similarly spirited debate - modernizers and economists will find themselves lined up against the veteran flyboys and bomber commanders determined to argue that you can't win a war without air power.