In August of 1962 the Soviet Union secretly began to build bases in Cuba for a number of medium-range and intermediate-range ballistic nuclear missiles with the ability to strike most of the continental United States. Since both countries in conflict were nuclear superpowers, their arsenal of missiles was large enough to destroy most of the developed world. After careful consideration and consultation with his advisers, President Kennedy imposed a naval quarantine around Cuba, a neutral yet very decisive move. He wanted to prevent the arrival of more Soviet offensive weapons on the island without starting a war. With Russian warships and transport vessels already on the course for Cuba, the world was hours away from a nuclear disaster. Read more about the Cuban missile crisis.