The second war, the Vietnam War, was perhaps the third most visible war of the 20th century, after World War I and World War II. After the French withdrawal from its former colony, on 21 July 1954, Vietnam became partitioned into two halves, much like Korea, along the 17th parallel. Fighting between North and South eventually escalated into a regional war. The United States provided aid to South Vietnam and contributed to propaganda efforts against the North, but was not directly involved until the Gulf of Tonkin Resolution, passed in reaction to a supposed North Vietnamese attack upon American destroyers, brought the U.S. into the war as a belligerent. The war was initially viewed as a fight to contain communism (see containment, Truman Doctrine, and Domino Theory), but, as more Americans were drafted and news of events such as the Tet Offensive and My Lai massacre leaked out, American sentiment turned against the war. U.S. President Richard Nixon was elected partially on a promise to end the war. This Nixon Doctrine involved a gradual pullout of American forces; South Vietnamese units were supposed to replace them, backed up by American air power. The plan went awry, with Nixon deliberately sabotaging peace talks for political gain, and the war spilled into neighboring Cambodia while South Vietnamese forces were pushed further back. Eventually, the U.S. and North Vietnam signed the Paris Peace Accords, ending U.S. involvement in the war. With the threat of U.S. retaliation gone, the North proceeded to violate the ceasefire and invaded the South with full military force. Saigon was captured on April 30, 1975, and Vietnam was unified under Communist rule a year later, effectively bringing an end to one of the most unpopular wars of all time.