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 upset when in September, the US Congress approved Joint Resolution 230, which expressed Congress's resolve to prevent the creation of an externally-supported military establishment. On the same day, the US announced a major military exercise in the Caribbean, PHIBRIGLEX-62, which Cuba denounced as a deliberate provocation and proof that the US planned to invade Cuba. The Soviet leadership believed, based on its perception of Kennedy's lack of confidence during the Bay of Pigs Invasion, that he would avoid confrontation and accept the missiles as a "fait accompli". On September 11, the Soviet Union publicly warned that a US attack on