After nikita Khrushchev`s memoir, he came up with the idea of placing nuclear missiles on the intermediate routes in Cuba in May 1962 in order to counter an emerging U.S. advance in the development and use of strategic missiles. He also presented the program as a way to protect Cuba from another U.S.-sponsored invasion, such as the failed attempt at the Bay of Pigs in 1961. Khrushchev sent another letter in which he asked for stricter conditions, such as the withdrawal of American missiles from Jupiter from Turkey. On October 24, Khrushchev responded to the Kennedy Embassy by declaring that the American “blockade” was an “act of aggression” and that Soviet ships enthrlying Cuba were responsible for continuing. Nevertheless, some vessels diverted from the quarantine line on 24 and 25 October; Others were arrested by U.S. naval forces, but they did not contain offensive weapons and could continue in this way. Meanwhile, U.S. reconnaissance flights over Cuba indicated that Soviet missile sites were approaching the state of alert.
As there was no apparent end to the crisis, U.S. forces were placed on DEFCON 2, meaning that a war with Air Strategic Command was imminent. On October 26, Kennedy told his advisers that only a U.S. attack on Cuba would remove the missiles, but insisted on giving the diplomatic channel a little more time. The crisis had reached a virtual stalemate. Khrushchev knew he was losing control. President Kennedy had been declared in early 1961 that a nuclear war would likely kill a third of humanity, with most or all of these deaths focusing on the United States, the USSR, Europe and China;  Khrushchev may have received similar reports from his army. OPLAN 312, primarily an air cargo operation of the Air Force and Navy, has been developed with sufficient flexibility to do everything in its power, from the inclusion of individual missile sites to air support for OPLAN 316 ground troops.  The United States had sent U-2 surveillance to Cuba since the failed Bay of Pigs invasion.  The first edition, which resulted in a disruption of reconnaissance flights, took place on 30 August, when a U-2 from the US Air Force`s Strategic Air Command accidentally flew over Sakhalin Island in the Soviet Far East. The Soviets protested and the United States apologized. Nine days later, a Taiwan-operated U-2 was lost over western China by an SA-2 surface-to-air missile.
U.S. officials feared that one of Cuba`s Cuban or Soviet SAMs could blow up a CIA U-2 home, which could lead to another international incident. On 10 September, during a meeting with members of the Waste Recognition Committee (COMOR), Foreign Minister Dean Rusk and National Security Adviser McGeorge Bundy severely restricted U-2 flights over Cuban airspace. The resulting lack of coverage of the island over the next five weeks has been known by historians as the “Photo Gap”.  No significant U-2 coverage was achieved within the island. U.S. officials attempted to use a Corona photo recognition satellite to gain coverage of reported Soviet military operations, but images taken on October 1 by a Corona KH-4 mission over western Koba were heavily covered with clouds and jams and did not provide valuable intelligence.  In late September, a navy reconnaissance aircraft photographed the Soviet ship Kasimov with large crates on its deck in the size and shape of the il-28 bombers.  On the other hand, Castro was convinced that the invasion of Cuba was imminent, and on 26 October he sent a telegram to Khrushchev, who, in the event of an attack, seemed to demand a pre-emptive nuclear attack against the United States.
In a 2010 interview, Castro lamented his earlier stance on the first use: “After seeing what I saw and knew what I know now, it wasn`t worth it.”  Castro also ordered to launch all anti-aircraft weapons in Cuba on all U.S. aircraft:[