As an army tank commander in the first Gulf War, John Nagl was an early convert to the view that America's greatest future threats would come from guerrillas, terrorists and insurgents. His Oxford thesis on the lessons of Vietnam became the bible of the counterinsurgency movement. But it would take 9/11 and the botched aftermath of the Iraq invasion to give his ideas contemporary relevance. After a year's fighting in Iraq he helped write core doctrine that would change the course of two wars and the thinking of an army. Knife Fights is the definitive account of counterinsurgency.