During the mid-1950s, the U.S. Air Force officer Edward Lansdale served as the CIA’s liaison to South Vietnamese President Ngo Dinh Diem. Lansdale ran a range of covert operations to weaken communist influence in the country and encouraged Diem to do more to earn the respect of his people. Lansdale was wary of the use of brute force, and his early career in advertising had given him an interest in the psychology of warfare. His efforts in South Vietnam gained him a reputation as a man who did his best to understand the countries in which he operated and who looked for innovative ways to undermine insurgencies. He urged the United States to support Diem, and when Diem was assassinated, in 1963, he considered it a disaster. After Diem’s death, Lansdale despaired over the persistent corruption of the new South Vietnamese leaders whom he was attempting to build up. In this sympathetic and revealing biography, Boot draws on his past work on guerrilla warfare to argue that adopting Lansdale’s “hearts and minds” approach might have caused less pain. But Boot is properly cautious, declining to firmly conclude that such a strategy would have resulted in a different overall outcome.