When the U.S. Seventh Fleet embarked the last of 50,000 Vietnamese evacuees, got underway from Vietnam's southern coast, and set a course for the Philippines on the evening of 2 May 1975, it marked the end of America's longest war. For more than 25 years, the United States and its allies had fought to preserve the independence of free governments in South Vietnam, Laos, and Cambodia, but that effort had failed. Vietnamese, Laotian, and Cambodian Communist movements and military forces now held sway over the entire Indochinese peninsula. The struggle for Southeast Asia, however, was only one...