The Cuban Missile Crisis was a confrontation between the United States and the Soviet Union in October 1962. The situation escalated into an international crisis when American missiles in Italy and Turkey were matched by Soviet deployments of similar ballistic missiles in Cuba.
The crisis was avoided when the USSR withdrew its weapons from Cuba and the United States secretly agreed to dismantle all nuclear medium-range ballistic missiles which had been deployed to Turkey for targets in the Soviet Union.
The Cuban missile crisis is often considered the closest the Cold War came to escalating into a full-scale nuclear war.
Source: Wikipedia