American grand strategy has undergone repeated changes in recent years. This essay clarifies the nature of those changes and offers an explanation for them. US foreign policymakers have had four basic strategic alternatives: a strategy of disengagement; a strategy of balance of power; a strategy of primacy; and a strategy of liberal internationalism. The Bush administration experimented with two of these strategies, and initiated two major strategic adjustments after coming into power: the first, early in 2001, by moving from Clinton's liberal internationalist approach towards a strategy of realism; the second, after the terrorist attacks of 11 September 2001, by moving from a realist approach towards a strategy of American primacy. International structural pressures cannot explain why either of these changes occurred. The real explanation lies in the influence of distinctive policy ideas, as promoted by leading state officials. The irony of this twofold strategic adjustment is that the realists of the Bush administration have returned to many of the Wilsonian assumptions that characterised the Clinton years.