Fifty years ago William Appleman Williams published his seminal book, The Tragedy of American Diplomacy. Williams, one of the great chroniclers of twentieth century American history, explored the ideological roots of US foreign policy and the perils of American exceptionalism, despite the best of intentions. Today the fate of the US empire is far from certain. Many have argued that these are its twilight years. In his new book, The Limits of Power: The End of American Exceptionalism, Andrew Bacevich, a retired army colonel, in many ways updates Appleman's thesis and offers a compelling critique of empire and war in 21st century America. Less