Actually the Vietnam War began in 1945 when Truman ignored Ho Chi Minh's invocations of Washington and Jefferson that called on the US as liberator to back Vietnamese independence. Instead the Anglo-Americans used recently surrendered Japanese troops to prevent the Viet Minh from seizing power. America's transition from empire demolition to empire building was almost instantaneous and Vietnam was at the center of it. https://medium.com/lessons-from-history/mythbusting-tour-vietnam-a-war-with-no-winner-part-1-393f013bff01