The Vietnam War changed America. Americans once had trusted and believed in their government, but after the war, they were not as ready to believe whatever their politicians and military leaders told them. Although most Americans agreed that the United States was fighting the Vietnam War for just, noble, and unselfish reasons—to stop the spread of communism—midway through the war, most Americans viewed the war as a mistake.

To their dismay, Americans learned that they were not the almighty world power they believed themselves to be. As Johnson and Nixon repeatedly told their advisers, the United States had never lost a war before, and they did not want to be the first president to do so. Losing this war—despite the heroic, valiant, and outstanding efforts of the U.S. military— was a shock to most...