A conflict in Southeast Asia in which North Vietnam and its southern allies fought South Vietnam and the United States for two decades, ending in 1975 with communist victory — demonstrating the limits of conventional military superiority against determined guerrilla resistance and transforming American politics, society, and foreign policy.
The United States deployed more firepower in Vietnam than it had in the entire Second World War. It dropped three times as many bombs on Southeast Asia as all sides dropped during the Second World War combined. It lost. The Vietnam War forced a reckoning with the limits of military power that the United States had not faced before, and produced a transformation in American domestic politics and foreign policy whose consequences are still visible. Understanding why the most powerful military in the world lost requires understanding what the war actually was — not an American story with Vietnamese background, but a Vietnamese conflict that America entered, escalated, and eventually abandoned.