In mid-October 1962, the United States Armed Forces were placed on their highest state of readiness since World War II after photographs taken by reconnaissance aircraft revealed that Soviet missile sites were being constructed on the island of Cuban. President John F. Kennedy and the Department of Defense were determined to prevent the sites from becoming operational. Soviet Premier Nikita Khrushchev and his field commanders in Cuba, were equally determined that missile installations would be placed in Cuba and were prepared to use battlefield nuclear weapons to defend the island if the United States invaded. The U.S. military was placed on a DEFCON-3 alert and an armada of 300 U.S. Navy ships set sail for the Caribbean to enforce a blockade of Cuba with instructions to launch missiles, if so ordered, on a moment's notice. Additionally, 20 aircraft armed with nuclear bombs were in the air around the clock ready to strike the Soviet Union. The prevention of a nuclear holocaust depended entirely on which side would blink first - the Soviet Union or the United States.