Oct. 22, 1962 - American ships and planes began preparing tonight to impose a blockade of Cuba. U.S. forces are under orders to thwart any attempt to deliver offensive weapons to Havana. A Defense Department spokesman said that a large force of ships and planes concentrating in the Caribbean area had instructions to use force if necessary, including sinking of ships, to carry out President Kennedy’s orders for a “quarantine” of Cuba. The Pentagon said also that U.S. military units throughout the world, including the garrison in Berlin and the nuclear-armed Strategic Air Command, had been placed “on alert.” Dependents of servicemen at the Guantanamo Bay Naval Base in Cuba have been evacuated. The military forces at the base, which were previously put at 3,300 Naval officers and men and several hundred Marines, have been doubled. Air defense units in the U.S., particularly radar warning stations, interceptor aircraft, and ground-to-air missiles, “have been redeployed,” the Defense department said. The orders for additional defense precautions were taken on the basis of aerial photographic evidence of long-range ballistic missile bases and the arrival of Soviet Ilyushin-28 bombers in Cuba.