Early in the period, an active foreign policy was pursued to assist Western Europe and Asia recover from the devastation of World War II. The Marsall Plan helped Western Europe rebuild from wartime devastation. The main American goal was to contain the expansion of Communism, which was controlled by the Soviet Union until China broke away about 1960. An arms race escalated through increasingly powerful nuclear weapons. The Soviets formed the Warsaw Pact of European satellites to oppose the American-led North Atlantic Treaty Organization (NATO) alliance. The U.S. fought a bloody, inconclusive war in Korea and was escalating the war in Vietnam as the period ended. The Communists took power in Cuba, and when the USSR sent in nuclear missiles to defend it, the Cuban Missile Crisis of 1962 was the most dangerous point of the era.