The Vietnam War, the longest war in American history, left a permanent scar on the American psyche. American advisors, following the general United States foreign policy after World War II of the containment of communism, began in 1950 to aid French forces seeking to maintain their colonial presence in Vietnam. Vietnamese Communists sought to oust the French. In 1954, the French lost on the battlefield. Negotiations in Paris resulted in the South’s being ceded to colonial forces and the North’s being ceded to the Vietminh. Where the French no longer wished to tread, the Americans stepped in, supporting the government of the South as the French left in 1954. American military and civilian advisors came to Vietnam in increasing numbers. In 1965, after years of mounting conflict, regular United States Army forces began an open, direct, and undeclared war against Communist North Vietnamese forces. United States participation in the controversial war continued until 1973, when a peace treaty was signed in Paris. Without U.S. military support, the government of the South did not last long. The North gained victory over the South in April, 1975, resulting in massive, panic-stricken evacuations of remaining U.S. personnel and of Vietnamese members and supporters of the Southern government. In the eyes of many, the United States lost a war for the first time in Vietnam.