Nuclear War, Prevention of Accidental. The outbreak of accidental nuclear war has been a looming fear in both popular and governmental circles since World War II. American efforts to avert accidental nuclear war have focused on four possible scenarios: unauthorized use of nuclear weapons; mechanical failure leading to detonation; false warning of imminent enemy attack; and misperception of an international incident or within an international crisis escalating to nuclear exchanges.

Avoiding unauthorized use of nuclear weapons is part of the larger issue of whether control of America's nuclear arsenal should rest in civilian or military hands. President Harry S. Truman institutionalized civilian control in the 1946 Atomic Energy Act, fearing that in the event of crisis or war the military might use nuclear weapons without civilian approval. To some degree, civilian control of nuclear weapons eroded in the 1950s, as global stationing of nuclear weapons and desires for military flexibility encouraged greater delegation of nuclear control to the military.

By the end of the administration of President Dwight D. Eisenhower (1953–61), civilians moved to reassert greater control and reduce the possibility of unauthorized use. In the late 1950s, the so‐called “two‐man rule” was installed, which required the simultaneous actions of two individuals to fire any nuclear weapon, thereby reducing the risk that a single deranged officer or unauthorized civilian would detonate a nuclear weapon. In 1962, most nuclear weapons were fitted with Permissive Action Links (PALs), which were essentially combination locks: entering the proper sequence of numbers was required to arm the warhead. PALs guard against unauthorized use by limiting the number of people who can physically detonate a nuclear weapon. Significantly, PALs were not installed on all nuclear weapons, naval nuclear weapons being the notable exception. Other policies have been implemented to reduce the risks of unauthorized use or mechanical accident, including the Personnel Reliability Program, which is designed to weed out unstable or unreliable individuals with nuclear weapons responsibilities, and the Enhanced Nuclear Detonation System, which provides mechanical safeguards to reduce the possibility of accidental or unauthorized detonation.

In preparing systems to warn of an enemy nuclear attack, American policymakers have pursued two goals: reducing the possibility that a nuclear attack on the United States would go undetected while at the same time avoiding false warnings of such an attack. The United States has invested substantial resources in warning systems, such as the DEW (distant early warning) line, a chain of radar installations across Alaska, Greenland, and Canada, which became operational in 1957 to detect a Soviet nuclear attack on North America. As the arms race escalated, American policymakers became increasingly concerned with the vulnerability of U.S. nuclear forces, worrying specifically that short warning of a Soviet nuclear attack would mean the destruction of U.S. nuclear forces before they could be used. Some critics argued that in response to these fears, the United States in the later years of the Cold War adopted a de facto policy of launch on warning (LOW), which called for American nuclear retaliation on the basis of only the warning of an impending Soviet attack, that is, before the confirmed detonation of Soviet nuclear weapons on American territory. Though the American military has taken some actions to reduce the probability of false warning of in coming nuclear attack through, for example, redundant systems, many argue that LOW introduces grave risks of accidental war, as nonmilitary events (such as a passing flock of geese) might be mistaken for an incoming nuclear attack, forcing a decision to retaliate before a warning could be confirmed. The dangers of LOW demonstrate that the two goals of a warning system, providing timely alert of an attack and avoiding false alarms, can be at odds with each other.

Decision makers have also been concerned that an international crisis or incident might inadvertently escalate to war. The United States has signed a number of international agreements designed to facilitate communication between nations to reduce the chances that one side will misinterpret the actions of another side as hostile or threatening. Most famously, a hot line providing direct communication between the United States and the Soviet Union was established after the Cuban Missile Crisis (1962–63). It was used during the 1973 Yom Kippur War. Additionally, a number of confidence‐building measures have been established to increase the transparency of each side's intentions and forces and to facilitate the resolution of minor but potentially dangerous incidents. Two examples are the 1971 Agreement on Measures to Reduce the Risk of Outbreak of Nuclear War and the 1972 Agreement on the Prevention of Incidents at Sea. The 1972 agreement was directed at the specific problem of naval encounters: during the Cold War, peacetime naval maneuvers of the two superpowers produced a number of incidents that might have led to real armed clashes.

The end of the Cold War saw an acceleration of activity aimed at reducing the threat of accidental nuclear war. In 1991, the United States began to implement the Cooperative Threat Reduction (CTR) program to assure that nuclear weapons and radioactive materials in the former Soviet Union were handled safely and securely. The United States and Russia agreed in 1994 to “detarget” their nuclear forces, reducing the chances that an accidental missile launch would hit the other country and touch off a nuclear war. The United States also moved to expand its security dialogue with the People's Republic of China, in 1997, gaining a Chinese‐American Incidents at Sea agreement and establishing a China‐U.S. hot line.

Significantly, scholars are divided on the usefulness of measures to prevent accidental nuclear war. Some point to successes in a number of areas; others argue that the risks of accidental or preemptive nuclear war are extraordinarily low; still others argue that some measures taken to reduce the risks of accidents are ineffective or may even cause potentially dangerous episodes. Advocates of this last position propose, for example, that attempts to build redundancy into nuclear weapons systems can produce excessive complexity and unexpected interactions that can generate incidents raising the risks of accidental nuclear detonation. Accidental nuclear war remains a frightening specter.
[See also Air and Space Defense; Arms Control and Disarmament: Nuclear; Cold War: External Course; On‐Site Inspection Agency; Strategy: Nuclear Warfare Strategy.]

Bibliography

Paul Bracken , The Command and Control of Nuclear Forces, 1983.
Daniel Ford , The Button: The Pentagon's Strategic Command and Control System, 1985.
Ashton B. Carter, John D. Steinbruner, and Charles A. Zraket, eds., Managing Nuclear Operations, 1987.
Peter Douglas Feaver , Guarding the Guardians: Civilian Control of Nuclear Weapons in the United States, 1992.
Bruce G. Blair , The Logic of Accidental Nuclear War, 1993.
Scott D. Sagan , The Limits of Safety: Organizations, Accidents, and Nuclear Weapons, 1993.

Dan Reiter