The Cold War - the 44 years of great power tension after World War II - did not see a formal state of war between the U.S. and USSR. However, "proxy wars" fought by the clients of each superpower and conflicts occurring in the wake of decolonization killed millions in Asia, Africa, and Latin America. Ironically, Europe, caught in the stalemate between the United States and the Soviet Union enjoyed its longest time of peace in recorded history. Washington and Moscow led their allies through the postwar decades with a mixture of aggressiveness and wisdom. From the first, the west's economic and social structures were more productive than those of the eastern bloc. Yet through a massive effort, the Soviet Union achieved military parity with the west by the mid-1970s. By the last decade of the twentieth century, economic exhaustion brought an end to the Cold War. Increased cooperation characterized the relations between Moscow and Washington, as both looked to a new era in which they would try to keep their dominant roles in the world. When North Korea ignored the UN's demand, the Security Council sent troops to help the South Korean government. Three years of costly fighting followed, in what the UN termed a "police action." UN forces led by the United States, which suffered over 140,000 casualties, repelled the invaders, who were supported by the USSR and the Chinese Peoples' Republic. An armistice was signed in July 1953, after Stalin's death in March and the U.S. threat to use nuclear weapons against China. ^6 The border between the two parts of the country was established near the 38th parallel, and South Korea's independence was maintained. The peninsula remained a crisis point for the next 40 years. [Footnote 6: Joseph L. Nogee and John Spanier, Peace Impossible - War Unlikely, The Cold War Between the United States and the Soviet Union (Glenview: Scott, Foresman/Little, Brown, 1988), p. 67.] By 1953 the first phase of the Cold War was over. Both the Soviet Union and the United States possessed terrifying arsenals of nuclear weapons, both competed in all aspects of the Cold War, and both constantly probed for weaknesses in the other's defenses. Varied forms of controlled conflict characterized the next four decades of relations between Moscow and Washington.