The second leg of the triad are intercontinental ballistic missiles or ICBMs. They did not start to play a role as a nuclear deterrent until 1962, when the Titan II was first tested. ICBMs are land-based missiles, located in both the U.S. and the U.S.S.R. They are large, long-range missiles, capable of reaching speeds of more than 20 times the speed of sound. ICBM flight time from the U.S. to the U.S.S.R., or vice versa, is about 30 minutes. Missile technology focuses on several issues: accuracy, warhead size and amount, and launch-weight capacity.
