This was the closest the world came to a nuclear war between the United States and the Soviet Union. The crisis began when the United States discovered that the Soviet Union was building nuclear missile sites in Cuba, just 90 miles from Florida. President John F. Kennedy ordered a naval blockade of Cuba to prevent further Soviet shipments of nuclear weapons. The Soviet Union responded by sending submarines and warships to the area. For several days, the world held its breath as the two superpowers teetered on the brink of war. Ultimately, the Soviet Union agreed to remove its missiles from Cuba in exchange for a promise from the United States not to invade the island. The Cuban Missile Crisis is considered a turning point in the Cold War, as it showed that both sides were willing to risk nuclear war to protect their interests.