Clausewitz is often quoted but more often misunderstood. On Clausewitz presents his central ideas about war and politics--such as war as an instrument of policy, the concept of Absolute War, friction and the fog of war--in a clear and systematic fashion. It also presents the man, his life and the military and intellectual environment in which he produced his great work On War. A final section considers Clausewitz's relevance to the rapidly changing nature of war today.