During the Cold War, American troops and their allies fought Communist forces in Korea and Vietnam. The Korean War began in 1950, when the Soviets walked out of a U.N. Security meeting, removing their possible veto. Under a United Nations umbrella, hundreds of thousands of U.S. troops fought to prevent the takeover of South Korea by North Korea, and later, to invade the northern nation. After repeated advances and retreats by both sides, and the PRC People's Volunteer Army's entry into the war, the Korean Armistice Agreement returned the peninsula to the status quo in 1953.