The Cold War began after World War 2 as tensions grew between Western nations led by the US and Eastern nations dominated by the Soviet Union. The Soviets set up communist governments in Eastern Europe and divided Germany and Korea. This led to an arms race and conflicts like the Korean War as the two sides competed for influence and tried to contain the spread of the other's ideology through proxies. Key events that defined the Cold War included the Berlin Airlift, formation of NATO and the Warsaw Pact, and the Cuban Missile Crisis.