Answer:
He ordered the U.S. Navy to blockade Cuba.
Step-by-step explanation:
The crisis erupted after the U.S. intelligence discovered in the summer of 1962 that Soviet missiles were being installed in Cuba and the presence of Russian bombers Il-28. It was an unacceptable event for the secutiry and safety of the U.S. The purpose of the deployment was to deter an invasion of the island by American tropps; comandante Fidel Castros´s fears were fed by the failed Bay of Pigs invasion of 1961 organized by the CIA.
President John F. Kennedy demanded the withdrawal of the missiles from Cuba. He put the armed forces in alert and ordered a naval blockade of Cuba, "a naval quarantine," that was enforced and stopped some Soviet ships. There were negotiations with Moscow, but plans were made for a strike on Cuba. The world came closest to nuclear war in those days of the Cold War.
In the tense negotiations, Soviet secretary-general and top leader Nikita Khrushchev demanded that the US would not invade Cuba. Kennedy gave that guarantee. In the end, Khrushchev agreed to withdraw the missiles (without consulting Cuban communist leader Fidel Castro, that enraged him), and the American guarantee was given.