Is America an empire? Certainly not, according to the U.S. government. Despite the conquest of two sovereign states in as many years, despite the presence of more than 750 military installations in two-thirds of the world's countries and despite his stated intention "to extend the benefits of freedom ... to every corner of the world," George W. Bush maintains that "America has never been an empire". "We don't seek empires," insists Defense Secretary Rumsfeld. "We're not imperialistic." Nonsense, says Niall Ferguson. In Colossus he argues that in both military and economic terms America is nothing less than the most powerful empire the world has ever seen. Just like the British Empire a century ago, the United States aspires to globalize free markets, the rule of law and representative government. In theory it's a good project, says Ferguson. Yet Americans shy away from the long-term commitments of manpower and money that are indispensable if rogue regimes and failed states really are to be changed for the better. This, he argues, is an empire with an attention deficit disorder, imposing ever more unrealistic timescales on its overseas interventions. Worse, it's an empire in denial - a hyperpower which simply refuses to admit the scale of its global responsibilities. And this chronic myopia may also apply to American domestic politics. When overstretch comes, he warns, it will come from within - and it will reveal that the American Colossus has more than merely feet of clay.