The Vietnam War (1954–75) was a war like no other in American history. It was America's longest war: military advisors were in the country from 1954 until 1975, and actual combat troops were in the country from 1965 to 1975. For those government and military strategists who designed U.S. Cold War policy, defending South Vietnam was crucial. According to their thinking, South Vietnam was the first in a strategic line of dominoes (a metaphor that referred to the game in which the first falling domino triggers a long line of collapsing dominoes). In their thinking, should Vietnam fall to Communism, it might trigger a similar political shift in other small Asian nations. Yet from the time that combat troops landed at the South Vietnamese port of Da Nang, American policy was directly challenged and questioned by the largest and most dramatic antiwar protest movement in American...