The Vietnam War was the longest and most unpopular military conflict in U.S. history. More than 58,000 Americans were killed and 304,000 wounded, (up to 4 million Vietnamese were killed).

The war began soon after the 1954 Geneva Conference divided Vietnam at 17 N lat. into the Communist-supported Democratic Republic of Vietnam (North Vietnam) and the U.S. supported Republic of Vietnam (South Vietnam). Direct American involvement began in 1955 with the arrival of the first advisors. The first combat troops arrived in 1965 and fought until the cease-fire of January 1973. For the United States, the war ended with the withdrawal of American troops and failure of its foreign policy in Vietnam. The length of the war, the high number of U.S. casualties, and the exposure of U.S. involvement in war crimes such as the massacre at My Lai turned many in the United States against the war.