The essays collected together in this volume are the result of many years reflecting on a country that is more than just a nation-state but is, what I would prefer to call, an empire. Some would no doubt question this designation. Some would even argue that it makes no sense at all calling the United States an empire when it doesn't control the territory of other countries and has never sent ‘settlers’ overseas to pacify other nations. My response is not to deny the obvious fact that the United States is not another British Empire or Washington another Rome – though there are some similarities between the two cities and both empires – but simply to observe that in terms of its military reach, its position at the centre of the world economy, its capacity to shape or limit the choices of others, and its promotion of a certain idea of modernity, the United States comes as close as anything in history to resembling what I would call an empire. As one wit once put it, ‘if it looks like a duck, swims like a duck and quacks like a duck’ then it is almost certainly a duck. Many might prefer that America was not so influential and have been predicting – perhaps even looking forward to – its decline for the better part of half a century. Others even wonder whether we should even call it an empire at all when we have so many other terms at our disposal such as superpower or hegemon. But empire in my view captures something about the sheer power of the United States and the role it purports to perform – with ever-decreasing success – in the wider international system.

Many of the ideas here have benefited from lengthy discussions and debates with a whole range of writers and academics, many but not all American, covering the spectrum from radical to neoconservative, liberal to realist with a dash of ‘English School’ thrown in for good measure! Some of the thoughts expressed here also build on work I have done at Chatham House over the years, so special thinks must go to it and its directors for indulging me for so long.