Empire is back. Once upon a time, in the era of decolonization, empires seemed like remnants of a past that would soon disappear. No more. Now, both as a reality of modern geopolitics and as a subject of academic study, empires are flourishing as never before. Although the current global power with the greatest imperial pretensions is now facing increasing difficulties in subduing resistance in one of its remote frontiers, and the American public at home would just as soon forget about this adventure in delusion, the question of the suitability of the United States for an imperial role will not soon disappear. Furthermore, China's sustained rise to the ranks of a great world power has begun to raise questions about whether China, too, will take on an imperial role, as it needs to guarantee supplies of energy for its booming economy and engage in geopolitical competition with its rivals. Like many other empires, China has also had difficulty in gaining the allegiance of the peoples on its frontiers.