Cuban Missile Crisis established a naval blockade on October 22 to prevent further missiles from reaching Cuba; Oval Office tapes during the crisis revealed that Kennedy had also put the blockade in place as an attempt to provoke Soviet-backed forces in Berlin as well. The US announced it would not permit offensive weapons to be delivered to Cuba and demanded that the weapons already in Cuba be dismantled and returned to the Soviet Union. After several days of tense negotiations, an agreement was reached between US President John F. Kennedy and Khrushchev. Publicly, the Soviets would dismantle their offensive weapons in Cuba and
Cuban Missile Crisis U-2 by a Soviet missile violated direct orders from Moscow, and Cuban antiaircraft fire against other US reconnaissance aircraft also violated direct orders from Khrushchev to Castro. Second, the Soviets already had 162 nuclear warheads on Cuba that the US did not then believe were there. Third, the Soviets and Cubans on the island would almost certainly have responded to an invasion by using those nuclear weapons, even though Castro believed that every human in Cuba would likely die as a result. Khrushchev also knew but may not have considered the fact that he had submarines armed with nuclear weapons