The land-based ICBMs offered survivability and quick delivery of nuclear weapons over long distances. Throughout the Cold War, the accuracy, reliability, and flexibility of ICBM systems continuously improved. At the peak of the Cold War in 1984, the United States maintained 1,054 ICBMs deployed in underground silos, while the Soviets possessed 1,398 ICBMs deployed in silos and in rail and road-mobile systems.
Development of the ICBM began shortly after the end of World War II. ICBMs are normally defined as long-range missiles that can attack targets located great distances from their launch sites. In 1966, the Air University Aerospace Glossary defined ICBMs as those missiles with a range of 5,000 miles or more. Other sources have defined the ICBM as a missile with a range of 1,500–2,000 miles. The ICBMs deployed during the Cold War were configured with nuclear warheads.
Initial missile programs, especially in the United States, focused more on air-breathing, jet-powered cruise missiles than ballistic systems. By the late 1940s, however, both the United States and the Soviet Union had determined that ballistic missiles were better for long-range attack missions because flight times, survivability, and accuracy were much better than they were for slower, aerodynamic vehicles. By 1953, the development of smaller, lighter thermonuclear weapons made it possible to construct long-range missiles capable of delivering nuclear payloads. The earliest systems were complicated liquid-fueled missiles that employed liquid oxygen and kerosene or storable hypergolic chemicals (fuel and oxidizer that ignited and burned when mixed without a separate igniter) as propellants. The first versions were deployed on soft, above-ground launchers that required anywhere from fifteen minutes to several hours to prepare for launch. They were guided by ground-based radio guidance systems that limited the number of missiles that could be launched at a single time. The first U.S. operational ICBM system, the Atlas D, was a 75-foot-long missile weighing more than 250,000 pounds. It was housed in either above-ground gantries or ground-level concrete structures, known as coffins, with three missiles and one guidance system at each complex. The first American ICBM attained nuclear alert (ready) status in October 1959.
Inertial guidance systems replaced the radio systems early in the life of ICBMs, with only the Atlas D and Titan I deployed with radio guidance. The inertial system was more accurate and reliable than radio guidance and allowed missiles to be based individually, providing a higher survivability scenario during a nuclear exchange. The early U.S. liquid-fueled cryogenic missiles were expensive to maintain, had low reliability, and were not exceptionally accurate. These systems, the Atlas and Titan I, carried single four-megaton nuclear warheads. The United States was quick to replace these missiles with the solid-fueled Minuteman missile, and by 1965 all Atlas and Titan I missiles were removed from service, to be replaced by the Minuteman and the hypergolic-fueled Titan II.
These new systems were easier to maintain and required far fewer missile combat crew members and maintenance personnel to keep them on alert. They were also much more survivable, with hardened silos scattered over wide areas, and were accurate to within a few hundred feet of the target. The United States maintained a force of fifty-four Titan II missiles, each with a nine-megaton warhead, on alert from the early 1960s to the mid-1980s. The Minuteman, which was developed in three versions (I, II, and III), first came on alert in 1962.
By 1967, 1,000 Minuteman missiles were on alert at six U.S. bases. The Minuteman I and II had single warheads of about 1.1 megatons, while the Minuteman III featured a multiple independently targeted reentry vehicle (MIRV) system equipped with up to three warheads of either 170 or 340 kilotons of yield. The entire force of Minuteman and Titan II missiles could be launched in a matter of minutes after the decision to execute was made. In the late 1980s, 50 Minuteman missiles at F. E. Warren Air Force Base, Wyoming, were replaced by 50 Peacekeeper missiles, a larger system that could carry up to ten 300-kiloton warheads capable of hitting ten different targets.
The Soviets developed more varieties of missiles than did the Americans, early on relying on both cryogenic and hypergolic storable propellant systems. As with the United States, the Soviet Union quickly realized that the cryogenic systems were slow to launch and hard to maintain, but, unlike the United States, Russia concentrated on ICBM designs in the 1960s through the 1980s that featured storable liquid-fueled systems, with missiles deployed both in underground silos and in mobile launchers. The first Soviet ICBM, the SS-7 (known to the Soviets as R-16), employed storable propellants and was first put on alert on 1 November 1961.
The Soviets were slower to adopt solid-fueled ICBMs but replaced their second- and third-generation liquid-fueled missiles with systems similar to the Minuteman and Peacekeeper systems. Soviet warheads were generally in the 1-megaton range, but two Soviet ICBMs (the SS-9 and SS-18) carried enormous 25-megaton warheads. In 1984, at the peak of the Cold War, the Soviets had 1,398 ICBMs deployed, including 520 SS-11s, 60 SS-13s, 150 SS-17s, 308 SS-18s, and 360 SS-19s.
China tested its first missile in 1960 but did not complete development and testing of an ICBM until 1980. China's first ICBM was liquid-fueled. China did not develop a solid-fueled ICBM until the early 1990s. Compared to the United States and the Soviet Union, the Chinese have maintained a very small ICBM force, with most of the emphasis on countering the threat posed by the Soviet Union rather than any threat by the United States.
Strategic arms limitation and reduction agreements between the United States and Russia resulted in a significant reduction in the number of ICBMs. The United States reduced its force to only 500 Minuteman III missiles, which will eventually have only one warhead apiece. All Minuteman II missiles were removed and the silos destroyed at three bases between 1994 and 1998, and Peacekeeper missiles were removed between 2002 and 2007. At the end of 2002, the Russians maintained a force of 709 ICBMs, a mix of SS-18, SS-19, SS-24, SS-25, and SS-27 liquid- and solid-fueled missiles in silos or mobile launchers.
Charles G. Simpson
Levi, Barbara G., et al., eds. The Future of Land Based Ballistic Missiles. New York: American Institute of Physics, 1989.; Neufeld, Jacob. The Development of Ballistic Missiles in the United States Air Force, 1945–1960. Washington, DC: Office of Air Force History, 1989.