At the height of the Cuban Missile Crisis, it took nearly twelve hours for Washington to receive Soviet Premier Nikita Khrushchev's initial 3,000-word response to President John F. Kennedy's ultimatum. By the time the White House had written a response, it had received a second, much tougher response. Convinced that faster, more direct communication might have ended the showdown earlier, Kennedy administration officials proposed the hotline to Moscow, which readily embraced the concept. Although few particulars of the hotline are known, it is believed to have been encrypted with a virtually fool-proof system. The hotline was first used during the 1967 Arab-Israeli War to be sure that each side was aware of the other's military moves in response to the crisis.
Paul G. Pierpaoli Jr.
Brugioni, Dino A. Eyeball to Eyeball: Inside the Cuban Missile Crisis. New York: Random House, 1993.