Clausewitz's On War has, at least until very recently, been regarded as the most important work of theory on its subject. But since the end of the Cold War in 1990, and even more since the 9/11 attacks on the United states in 2001, an increasing number of commentators have argued that On War has lost its analytical edge as a tool for understanding war. They have argued that Clausewitz was concerned solely with inter-state war and with properly defined...