The United States and the Soviet Union were on the verge of nuclear conflicts just 55 years ago, and many know it as The Cuban Missile Crisis.

On Oct. 14, 1962, during the Cold War, a high-altitude U-2 spy plane provided photos of undeniable evidence that the Soviet Union made medium-range missiles capable of carrying nuclear warheads in Cuba; not only did they exist, but they were located just 90 miles off the American coastline, stated history.com.

During the Bay of Pigs invasion in April of 1961, U.S.-trained Cuban refugees attempted to overthrow Fidel Castro’s government after landing in Cuba, which created tension between both the U.S. and the Soviet Union. The invasion was unsuccessful, history.com stated, but Castro suspected they would try again, so he seeked military assistance from the Soviet Union.

Although the missile sites in Cuba were incomplete, they were almost finished, and they had the capability to strike major cities in the U.S.. Just two days after the photos were found, they were given to President John F. Kennedy, and in the weeks following, the U.S. and the Soviet Union came the closest they’ve ever been to a nuclear war.

After the U-2 spy plane discovered the Cuban missile sites, President Kennedy developed a group called ExCom, which was comprised of an executive committee of senior military, political and diplomatic advisers to discuss how to respond to the nuclear disaster that was on the brink of occurring.

In order to prevent transportation of any other weapons from the Soviet Union to Cuba, President Kennedy ordered “a naval ‘quarantine’….The president made it clear that America would not stop short of military action to end what he called a ‘clandestine, reckless, and provocative threat to world peace,’” as stated on history.com.

On Oct. 23, the quarantine began, but President Kennedy decided to pull the line back by 500 miles to give Soviet leader Nikita Khrushchev more time to consider his actions. All ships that were traveling to Cuba at the time seemed to back off, except for one, the tanker Bucharest, stated history.com.

United Nations Secretary General U Thant urged both the United States and Soviet governments to “refrain from any action that may aggravate the situation and bring with it the risk of war.”

Still though, U.S. military commanders began preparing for a full-scale war with the Soviet Union, and DEFCON 2 was issued, which is “the highest military alert ever reached in the postwar era,” according to history.com. Two U.S. aircrafts attempted to stop the Bucharest as it began to cross over the U.S. quarantine, but the efforts weren’t successful.

Eventually, President Kennedy discovered the construction of the missile bases had continued, so ExCom debated a U.S. invasion of Cuba. However, the same day, the Soviet Union proposed ending the crisis and said they would remove the missile bases if the U.S. pledged not to go through with the invasion of Cuba.

Soviet leader Khrushchev, then, called for the disassembling of U.S. missile bases in Turkey the next day, and additionally, one of the U-2 spy planes was shot down over Cuba, which killed the pilot Major Rudolf Anderson. Because of this, history.com stated, Kennedy avoided any more military retaliation, and he agreed to disassemble the missile sites in Turkey at a later date.

On Oct. 28, the Cuban Missile Crisis came to a close, and Khrushchev agreed to dismantle their weapons in Cuba, and they began removal that afternoon. At this point, the world could breathe again, and a nuclear war had been avoided. Not long after, the U.S. also began to remove their missile bases in Turkey.

The relationship between the U.S. and the Soviet Union remained quite rocky for some time after the Cuban Missile Crisis, but in the 1970s, the Soviet Union build “intercontinental ballistic missiles capable of striking any city in the United States,” signaling nuclear parity with the U.S., stated history.com.

In 2015, relations between the U.S. and Cuba became normalized, as travel restrictions eased up, embassies opened and diplomatic missions opened up as well.

Jessica Ricard can be contacted at jricard@kscequinox.com