From one of the most important army officers of his generation, a memoir of the revolution in warfare he helped lead, in combat and in WashingtonWhen John Nagl was an army tank commander in the first Gulf War of 1991, fresh out of West Point and Oxford, he could already see that America's military superiority meant that the age of conventional combat was nearing an end. Nagl was an early convert to the view that America's greatest future threats would come from asymmetric warfare—guerrillas, terrorists, and insurgents. But that made him an outsider within the army; and as if to double down on his dissidence, he scorned the conventional path to a general's stars and got the military to send him back to Oxford to study the history of counterinsurgency in earnest, searching for guideposts for America. The result would become the bible of the counterinsurgency movement, a book called Learning to Eat Soup with a Knife.But it would take the...