The Cold War was a period of tension between the US and USSR from 1945-1991. It was characterized by mutual suspicion and hostility as both countries had nuclear weapons. While direct conflict was avoided, they came close to war on occasions due to interfering in other countries' affairs during events like the Korean War and Cuban Missile Crisis. The origins of the Cold War began with disagreements over Eastern Europe and mistrust growing between Stalin and Truman. Containment became the US policy to prevent the spread of communism.