US global power, as presently conceived by the overwhelming majority of the US establishment, is unsustainable. To place American power on a firmer footing requires putting it on a more limited footing. Despite the lessons of Iraq, this is something that American policymakers - Democrat and Republican, civilian and military - still find extremely difficult to think about.

The basic reasons why the American empire is bust are familiar from other imperial histories. The empire can no longer raise enough taxes or soldiers, it is increasingly indebted and key vassal states are no longer reliable. In an equally classical fashion, central to what is happening is the greed and decadence of the imperial elites. Like so many of their predecessors, the US wealthy classes have gained a grip over the state that allows them to escape taxation. Mass acquiescence in this has to be bought with much smaller - but fiscally equally damaging - cuts to taxes on the middle classes.