arms controlany international control or limitation of the development, testing, production, deployment, or use of weapons based on the premise that the continued existence of certain national military establishments is inevitable. The concept implies some form of collaboration between generally competitive or antagonistic states in areas of military policy to diminish the likelihood of war or, should war occur, to limit its destructiveness.

In a broad sense, arms control grows out of historical state practice in disarmament, which has had, since the 20th century, a long record of successes and failures. A narrower definition of each term, however, reveals key differences between disarmament and arms control. Complete or general disarmament may involve the elimination of a country’s entire military capacity. Partial disarmament may consist of the elimination of certain types or classes of weapons or a general reduction (but not elimination) of all classes of weapons. Whereas disarmament agreements usually directly prohibit the possession or production of weapons, arms-control agreements often proceed by setting limitations on the testing, deployment, or use of certain types of weapons. Arms-control advocates generally take a more or less realistic approach to international relations, eschewing pacifism in a world they view as anarchic and as lacking any central authority for settling conflicts. Furthermore, whereas the objective of disarmament agreements is the reduction or elimination of weapons, arms-control agreements aim to encourage countries to manage their weapons in limited cooperation with each other. Disarmament conferences with a large number of participants have often degenerated into public spectacles with shouting matches between the delegations of countries that have resulted in increased tensions. Nevertheless, arms-control efforts, particularly those between the United States and the Soviet Union during the Cold War, proved useful in limiting the nuclear arms race, and, by the end of the 20th century, the term arms control was often used to denote any disarmament or arms-limitation agreement.

Early efforts

The first international assembly that addressed the issue of arms control (among other issues) was the first Hague Convention (1899). Although this and later Hague conferences failed to limit armaments, they did adopt a number of agreements on territorial and functional matters. Other Hague conferences addressed issues of arbitration and principles and treaties of warfare. The Hague Convention approved prohibitions on the use of asphyxiating gases and expanding bullets (dumdums) and discharges of projectiles or explosives from balloons, though none of these agreements was observed during World War I. After the war, the Washington Conference (1921–22)—before adjourning early—reached disarmament, arms-limitation, and arms-control agreements aimed at halting the naval arms race between the world’s leading powers. The United States, the United Kingdom, France, Italy, and Japan agreed to limit the number and tonnage of their capital ships and to scrap certain other ships. At the London Naval Conference (1930), however, Italy and France refused to agree to an extension of the agreement, and Japan withdrew in 1935. In 1925 the Geneva Protocol, which now has some 130 parties, prohibited the use of asphyxiating and poisonous gases and bacteriological weapons in international conflicts, though it did not apply to internal or civil wars. Because many countries retained the right to use such weapons in a retaliatory strike, the Geneva Protocol came to be seen as a broader and more effective agreement that included prohibitions of using such weapons in a first strike.

The Cold War: Soviet and U.S.-led arms-control agreements

World War II, during which some 40 to 50 million people died, was by far the bloodiest conflict in human history. The conclusion of the Pacific phase of the war ushered in the atomic age as the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki in 1945. Two of the victor states, the United States and the Soviet Union, soon began to develop large arsenals of nuclear weapons. The possibility of the mutual destruction of each country by the other in an intercontinental exchange of nuclear-armed missiles prompted them to undertake increasingly serious negotiations to limit first the testing, then the deployment, and finally the possession of these weapons. As precursors, the International Atomic Energy Agency (IAEA) was established in 1957 as an autonomous intergovernmental body, under the auspices of the United Nations, to promote peaceful uses of nuclear technology and to prevent the use of such technology for military purposes; and in 1959 the Antarctic Treaty, signed by 12 countries, including the United States and the Soviet Union, internationalized and demilitarized Antarctica and paved the way for future arms-control agreements between the Soviet Union and the United States. Many of the arms-control agreements of the Cold War period focused on mutual deterrence, a strategy in which the threat of reprisal would effectively preclude an initial attack.

U.S. Presidents Dwight D. Eisenhower and John F. Kennedy considered treaties that sought to control the production of weapons in an attempt to avoid a nuclear conflict. (Kennedy, in particular, was concerned with nuclear proliferation by the People’s Republic of China.) During the Cuban missile crisis (1962), a new series of arms-control issues appeared, including the need for diplomatic communication to avert potential nuclear catastrophe. Beginning in the 1960s, the United States and the Soviet Union sponsored several international arms-control agreements designed to be of limited risk to each side. The first of these, the partial Nuclear Test-Ban Treaty (1963), prohibited tests of nuclear weapons in the atmosphere, in outer space, and underwater, which thus effectively confined nuclear explosions to underground sites. The Outer Space Treaty (1967) further limited the deployment of nuclear weapons and other weapons of mass destruction by banning countries from placing them in orbit. In 1968 the two superpowers took the lead in establishing the Treaty on the Non-proliferation of Nuclear Weapons (Non-proliferation Treaty; NPT), whereby they agreed not to promote the spread, or proliferation, of nuclear weapons to countries that did not already possess them. Two classes of states are parties to the NPT: those possessing nuclear weapons, such as China, France, Russia, the United Kingdom, and the United States, and nonnuclear states. The treaty, originally signed by 62 countries, had grown to some 185 parties by the early 21st century, although declared or suspected nuclear states such as India, Pakistan, and Israel were not parties. The NPT became effective in 1970 for a 25-year period; it was extended indefinitely in 1995.

During the 1970s the Strategic Arms Limitation Talks (SALT) helped to restrain the continuing buildup by the Soviet Union and the United States of nuclear-armed intercontinental (long-range or strategic) ballistic missiles (ICBMs). One major part of the SALT I complex of agreements reached in 1972 severely limited each country’s future deployment of antiballistic missiles (ABMs), which could be used to destroy incoming ICBMs. The Anti-Ballistic Missile Treaty (ABM Treaty) provided that each country could have no more than two ABM deployment areas and could not establish a nationwide system of ABM defense; a protocol to the agreement, signed in 1974, limited each party to a single ABM deployment area. The ABM Treaty, which was predicated on the strategy of mutually assured destruction, ensured that each side would remain vulnerable to the other’s strategic offensive forces. Another part of the SALT I agreement froze the number of each side’s ICBMs and submarine-launched ballistic missiles (SLBMs) at current levels. The SALT II agreement (1979) set limits on each side’s store of multiple independent reentry vehicles (MIRVs), which were strategic missiles equipped with multiple nuclear warheads capable of hitting different targets on the ground. This agreement placed limits on the number of MIRVs, strategic bombers, and other strategic launchers each side possessed. Although the SALT agreements stabilized the nuclear arms race between the two superpowers, it did so at very high force levels, with each country continuing to possess many times the offensive capacity needed to utterly destroy the other in a nuclear exchange. (For a technical discussion of weapons systems, see the article rocket and missile system.)

During the 1970s the United States and the Soviet Union also facilitated the establishment of the Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on Their Destruction (1972). Commonly known as the Biological and Toxin Weapons Convention, the agreement supplemented the Geneva Protocol of 1925 and required all signatories both to refrain from developing and producing biological or toxin weapons and to destroy such weapons that they may possess that “have no justification for prophylactic, protective, and other peaceful purposes.” Since it entered into force in 1975, the convention has been reviewed several times in order to take into account new scientific and technological developments, though there is no method in place to monitor compliance.

In 1985 the accession in the Soviet Union of a liberalizing regime under Mikhail Gorbachev generated intensified arms-control negotiations between the two superpowers. The result of these efforts, the Intermediate-Range Nuclear Forces Treaty (1987), committed the United States and the Soviet Union to the complete elimination of their stocks of intermediate- and medium-range land-based missiles. In the meantime, a new set of bilateral negotiations between the superpowers had begun in 1982 with the aim of reducing rather than merely limiting their arsenals of nuclear warheads and launch platforms (missiles and bombers). These negotiations, called the Strategic Arms Reduction Talks (START), produced a treaty in 1991 that committed the superpowers to reducing their strategic nuclear forces by 25 to 30 percent over a period of years. The United States and the Soviet Union also began eliminating various types of tactical (battlefield) nuclear-armed weapons, including artillery shells, depth charges, land mines, bombs, and the warheads carried on various tactical missiles. The START agreement built on the Conventional Forces in Europe Treaty (1990), which committed the Warsaw Pact and the North Atlantic Treaty Organization to strict limits on the number of tanks, combat aircraft, armoured vehicles, and attack helicopters that each side could possess.

Recent efforts

Following the breakup of the Soviet Union in late 1991, newly sovereign Russia undertook efforts to drastically reduce its nuclear and conventional armed forces through unilateral actions and agreements with the United States. The newly independent republics of Ukraine, Belarus, and Kazakhstan inherited some of the Soviet Union’s nuclear arsenal but quickly pursued complete nuclear disarmament; all three became nuclear free by 1996. In 1992 an informal agreement (START II) was reached between the United States and Russia that would further drastically reduce each country’s strategic nuclear forces over a period extending into the early 21st century.

In the 1990s the United States and Russia played major roles in the conclusion of the Chemical Weapons Convention (1993), which prohibited the development, production, stockpiling, and use of chemical weapons and called for the destruction of existing stocks within 10 years. The convention, drafted by the 39 countries of the Conference on Disarmament and entering into force in 1997, reaffirmed the Geneva Protocol of 1925, restated the prohibitions of the Treaty of Versailles (1919) and the Washington treaties (1921–22) against the use of poisonous gases, and added a ban on bacteriological warfare; some 150 states were party to the agreement by the early 21st century. The 1996 Comprehensive Nuclear-Test-Ban Treaty, which would prohibit all forms of nuclear explosive testing, had been signed by more than 165 states and ratified by more than 100 by the early 21st century but had failed to enter into force because some of the 44 states whose signatures were required for its enactment (including the United States, China, India, Israel, North Korea, and Pakistan) chose not to sign. In 1997, as a result of efforts led by the International Campaign to Ban Landmines (ICBL), a treaty prohibiting the use of antipersonnel mines was negotiated; it went into effect in 1999, and, by the early 21st century, nearly 150 countries had signed it, though China, Russia, and the United States had not.

In June 2002, despite intense international opposition, the United States, citing fundamental changes in its security needs since the 1970s, withdrew from the ABM Treaty to pursue a national missile defense system designed to protect the country against nuclear attack. The United States subsequently offered to share defense technology with Russia and cover some of its allies, but the Russian response was lukewarm. Although Russia opposed the U.S. decision, its reaction was restrained; in May 2002, five months after the United States announced its intent to withdraw from the ABM Treaty, the two countries signed the Strategic Offensive Reductions Treaty, which committed each side to reducing its store of strategic nuclear warheads. Russia subsequently announced that it would no longer be bound by the START II agreement, which its parliament had ratified in 2000.

In May 2008, representatives of more than 100 countries met in Dublin to conclude an agreement that banned the use of cluster bombs, which release dozens of smaller bombs (“bomblets”) over a wide area. The Cluster Munition Coalition, a network of nongovernmental organizations including the ICBL and Amnesty International, had spearheaded efforts to prohibit the devices on the grounds that unexploded bomblets present a lethal risk to civilians long after a conflict has ended. The Cluster Munitions Convention was adopted despite opposition from the largest manufacturers and stockpilers of the weapons (including China, Russia, and the United States). It was scheduled to be opened for signature in December 2008 and would enter into force once 30 countries had ratified it.