On October 29, 1962, Cuba was invaded by the United States. Early the next morning, Fidel Castro asked Khrushchev to launch a first strike nuclear attack against the United States. Khrushchev, at this point prepared to exchange Cuba for Berlin to prevent the war from going nuclear, refused. Castro felt betrayed, and ordered his army to attack the Russians, seize the missiles, and fire them upon the United States. American troops were confused and terrified that the Cubans were killing the Russians. As this was happening, President Kennedy ordered the US military forces to be withdrawn from Cuba, though many Americans had already deserted, and the Cubans would launch missiles on the US before the Americans could get out anyway.