The Cold War began after World War 2 and resulted in the formation of two military alliances - NATO and the Warsaw Pact. Tensions escalated throughout the late 1940s and 1950s, including the Berlin Blockade and arms buildup. Major events of the early Cold War included the Cuban Missile Crisis and space race. Reformist leader Mikhail Gorbachev in the 1980s led to improved US-Soviet relations and the eventual dissolution of the Soviet Union, bringing the Cold War to an end.