During October 1962, the president of the United States, John F. Kennedy, announced that American reconnaissance aircraft had discovered missile sites in Cuba. The sites, capable of launching Soviet missiles on U.S. targets, were only 90 miles (140 kilometres) from the Florida coast. Soviet missile bases in Cuba would thus seriously undermine the effectiveness of the North American Air Defence (NORAD) Command.
President Kennedy ordered the United States Navy (USN) to blockade Cuba in order to prevent Soviet ships (already en route) from delivering missiles to the bases. He also warned the Soviet Union that the United States would consider any attempt to run the blockade as an act of war.
The Royal Canadian Navy (RCN) and Royal Canadian Air Force (RCAF) immediately took action to aid the USN in establishing the blockade. Although the RCN and RCAF did not act under specific orders from the federal cabinet, their commanders assumed responsibility for honouring the military commitment to their American ally. The RCN deployed 1 aircraft carrier, 13 destroyers, 9 frigates, 2 submarines, and 6 minesweepers. The RCN assumed USN patrol duties off the eastern coast of the United States so that the USN had more ships available to establish the blockade. RCN frigates were dispatched to the mid-Atlantic with 10 USN submarines to counter any moves by Soviet submarine forces. At the same time, the RCAF deployed 44 aircraft to patrol the North Atlantic and track any Soviet ships in the area.
The Soviet convoy did not attempt to challenge the blockading forces, and the crisis was over on 12 November. However, the American NORAD commander had immediately ordered DEFCON 3, the state of alert prior to actual war, without consulting or advising Canadian authorities.