From 1945 to 1991, the Cold War was the threat of nuclear war between rival powers, from the end of World War II until the collapse of the USSR. In 1948, when the Soviet Union cut off West Berlin, an emergency airlift kept the city supplied for 15 months. In October 1962, the Cuban Missile Crisis brought the world to the brink of war before the Soviets backed down and removed their missiles from Cuba. Competition also played out in the Olympics and the space race, while thousands of nuclear weapons were amassed to assure mutual destruction in an all-out war. The fall of the Berlin Wall in 1989 symbolized the end of the Cold War era. In 1991, a coalition of 28 U.S.-led nations, acting with U.N. sanction after Iraq's invasion of Kuwait, helped push Iraqi troops out of Kuwait. An economic embargo was authorized, then a month-long coalition air campaign using stealth planes and smart bombs was followed by a swift ground assault in February called Operation Desert Storm. Iraqi forces left hundreds of burning oil wells in their retreat, and after four days of battle coalition troops stopped short of taking Baghdad once their mission to liberate Kuwait had been achieved.