The work of Carl von Clausewitz continues to provoke heated debate. For some scholars, Clausewitz's On War remains indispensable to serious thought on the resort to war in the modern period. Others, however, see Clausewitz's work as either outdated, or a morally repellent argument for unlimited, unrestrained and brutal warfare. This essay argues not only that Clausewitz's work continues to be relevant to discussions on the use of armed force, but also that On War provides a framework for ethical reflection on war and its conduct. Two main preoccupations of western military academies and staff colleges--Clausewitz on the one hand, and the just war tradition on the other--can complement, rather than rival each other. On War creates a space for reflection on the use of armed force, and for that reason if no other, should still be considered an important resource for contemporary students and practitioners of strategy.