What happened during the Cuban Missile Crisis - the 13-day standoff that almost ended the world

A letter to Kennedy from Khrushchev detailed the agreement that the missiles would be removed from Cuba in exchange for a US promise not to invade.

Kennedy issued a statement applauding Khrushchev's decision to remove the missiles.

"This is an important and constructive contribution to peace," he said. "It is my earnest hope that the governments of the world can, with a solution of the Cuban crisis, turn their urgent attention to the compelling necessity for ending the arms race and reducing world tensions."

Khrushchev sent Kennedy another letter demanding stronger terms, such as the removal of the US's Jupiter missiles from Turkey.

An American U-2 plane was also shot down over Cuba by a Soviet-supplied missile. Its pilot, Major Rudolf Anderson, was killed.

Kennedy ultimately ignored the latest letter from Khrushchev, responding only to the warmer letter he had sent the previous day. "I have read your letter of October 26th with great care and welcomed the statement of your desire to seek a prompt solution to the problem," he wrote.

That evening, Attorney General Robert Kennedy and Soviet Ambassador Anatoly Dobrynin reached an agreement that the USSR would withdraw its missiles from Cuba under the supervision of the United Nations. In turn, the US would vow not to invade Cuba and remove its missiles from Turkey.

Castro, in his letter, explained to Khrushchev that should the US attempt to invade and occupy Cuba, the country would pose such a threat that the Soviet Union could not risk the possibility of a preemptive nuclear strike by the US.

"I tell you this because I believe that the imperialists' aggressiveness makes them extremely dangerous, and that if they manage to carry out an invasion of Cuba — a brutal act in violation of universal and moral law — then that would be the moment to eliminate this danger forever, in an act of the most legitimate self-defense. However harsh and terrible the solution, there would be no other," Castro wrote.

Meanwhile, Khrushchev wrote to Kennedy declaring he was willing to remove the missiles from the island if the United States would pledge never to invade Cuba.

Here's an excerpt of his letter: "I propose: We, for our part, will declare that our ships, bound for Cuba, will not carry any kind of armaments. You would declare that the United States will not invade Cuba with its forces and will not support any sort of forces which might intend to carry out an invasion of Cuba. Then the necessity for the presence of our military specialists in Cuba would disappear."

All but one of the Soviet vessels heading towards Cuba turned back. One freighter containing only petroleum products was allowed through the quarantine.

At the United Nations Security Council, US Ambassador Adlai Stevenson lambasted the Soviet Ambassador Valerian Zorin over the evidence of the missiles. Here's how the New York Journal-American newspaper characterized the confrontation:

"His face red with anger and his well-controlled voice shaking with emotion, Mr. Stevenson tossed diplomatic niceties aside and vowed he would wait 'until hell freezes over' for Zorin to give a 'yes or no' to his question whether there were Soviet missiles in Cuba. The Russian, in turn, called Mr. Stevenson a liar."

Here’s an excerpt: "You, Mr. President, are not declaring a quarantine, but rather are setting forth an ultimatum and threatening that if we do not give in to your demands you will use force. Consider what you are saying! And you want to persuade me to agree to this! What would it mean to agree to these demands? It would mean guiding oneself in one's relations with other countries not by reason, but by submitting to arbitrariness. You are no longer appealing to reason, but wish to intimidate us."

Kennedy then requested that Khrushchev halt any Soviet ships en route to Cuba, out of fear the US would be forced to exchange fire and launch a war between the two nations.

Here's an excerpt: 'In our discussions and exchanges on Berlin and other international questions, the one thing that has most concerned me has been the possibility that your Government would not correctly understand the will and determination of the United States in any given situation, since I have not assumed that you or any other sane man would, in this nuclear age, deliberately plunge the world into war which it is crystal clear no country could win and which could only result in catastrophic consequences to the whole world, including the aggressor.'

Kennedy forcefully addressed the public that evening on television, saying the quarantine would remain in place until the missile sites were dismantled and no additional weapons delivered to Cuba.

He added that any missile attack from Cuba would be interpreted as an attack from the Soviets, and would merit a "full retaliatory response" against the Soviets.

Here’s an excerpt from his speech: "This secret, swift, and extraordinary buildup of Communist missiles — in an area well-known to have a special and historical relationship to the United States and the nations of the Western Hemisphere, in violation of Soviet assurances, and in defiance of American and hemispheric policy — this sudden, clandestine decision to station strategic weapons for the first time outside of Soviet soil — is a deliberately provocative and unjustified change in the status quo which cannot be accepted by this country, if our courage and our commitments are ever to be trusted again by either friend or foe."

The Kennedy administration used the term "quarantine" rather than "blockade," as the latter would have legally implied a state of war. A quarantine, however, allowed the US to continue receiving the support of the Organization of American States, the 35-member continental organization.

Without revealing that he knew the extent of the nuclear arms build-up in Cuba, Kennedy repeated the warning he issued on Sept. 4, when he said the "gravest issues would arise" should offensive nuclear weapons be found on Cuba.

Kennedy, meanwhile, kept up a normal schedule, attending a church service, eating lunch with the Crown Prince of Libya, and traveling to Connecticut to campaign for congressional candidates.

Kennedy, anxious to maintain the appearance that the situation in the White House was business-as-usual, kept up his official schedule but met frequently with advisors to strategize.

The Joint Chiefs of Staff urged Kennedy to launch an air strike followed by a full-on invasion of Cuba, but others called for a naval quarantine.

President John F. Kennedy on Sept. 4 released a statement condemning the Soviet effort to boost Cuba’s military power, and said "the gravest issues would arise" should Cuba obtain offensive capability.

"It continues to be the policy of the United States that the Castro regime will not be allowed to export its aggressive purposes by force or the threat of force. It will be prevented by whatever means may be necessary from taking action against any part of the Western Hemisphere," Kennedy said.

"The United States, in conjunction with other Hemisphere countries, will make sure that while increased armaments will be a heavy burden to the unhappy people of Cuba themselves, they will be nothing more."

The move was partly an effort to deter the US from attempting another Cuban invasion, and partly a way to maximize the Soviet Union’s nuclear strike capability. Missile site construction began that summer.