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Since the advent of nuclear weapons in 1945, nations have endeavored, with mixed success, to negotiate ways to slow or halt the proliferation of nuclear weapons, as well as development and testing of new weapons. Most experts agree that though the history of arms control is checkered, international treaties have played a role in reducing the dangers of weapons of mass destruction.

The treaties that are "in the news" the most are the Anti Ballistic Missile Treaty (ABM), Treaty, Nuclear Nonproliferation Treaty (NPT) and Comprehensive Nuclear Test Ban Treaty (CTBT). The following is a chronological list of the primary strategic treaties of note and their current status.

Partial Test Ban Treaty (PTBT) (Entered into force 1963)
Following above-ground ("atmospheric") tests of very large (multi-megaton range) nuclear weapons in the 1950s, and several incidents where test fallout injured civilians, public pressure for an end to nuclear testing intensified. Physicians for Social Responsibility mounted a public disarmament campaign using evidence that strontium-90 from nuclear weapons tests had spread worldwide and reached measurable levels in babies' teeth. The Cuban Missile Crisis of October, 1962, added further impetus to end nuclear testing.

The Partial Test Ban Treaty of 1963 resulted from negotiations toward a Comprehensive Test Ban Treaty (see CTBT, below) The PTBT prohibits nuclear weapons tests "or any other nuclear explosion" in the atmosphere, in outer space, and under water. While not banning tests underground, the Treaty does prohibit nuclear explosions in this environment if they cause "radioactive debris to be present outside the territorial limits of the State under whose jurisdiction or control" the explosions were conducted.

Outer Space Treaty (Entered into force 1967)
The Outer Space Treaty is relevant to current discussions of national missile defense and the militarization of space. This treaty sought to prevent "a new form of colonial competition" in space. This Treaty restricts activities in two ways:

First, it contains an undertaking not to place in orbit around the Earth, install on the moon or any other celestial body, or otherwise station in outer space, nuclear or any other weapons of mass destruction.

Second, it limits the use of the moon and other celestial bodies exclusively to peaceful purposes and expressly prohibits their use for establishing military bases, installation, or fortifications; testing weapons of any kind; or conducting military maneuvers.

Nuclear Non-proliferation Treaty (NPT) (entered into force 1970; unlimited extension 1995)
This was a broad, international treaty to control nuclear proliferation. Periodic Review Conferences (1980, 1990 and 2000) assess progress (or lack thereof). 180 non-nuclear weapons countries have signed the treaty and committed themselves to a nuclear weapons- free status and to related inspections. The "Big 5"nuclear weapons powers (US, Russia, China, UK and France) pledged, in Article VI, to reduce and ultimately abolish their nuclear weapons (however there is no timetable). An unlimited extension of the treaty was achieved in 1995 with great difficulty, since the non-nuclear weapon states felt the nuclear weapon states had not fulfilled their commitment to reduce their arsenals sufficiently and failed to reduce tensions ( continuing high alert status for American and Russian weapons). Since then, several factors have combined which may unravel the NPT nonproliferation regime and lead to increased nuclear weapons proliferation in the future:

  • The 1999 US Senate vote against CTBT ratification
  • The probable withdrawal of the US from the ABM treaty and the imminent deployment of a national missile defense system by the US
  • The refusal of Israel, Pakistan and India to sign the NPT treaty

Article VI of the NPT:

"Each of the Parties to the Treaty undertakes to pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament, and on a treaty on general and complete disarmament under strict and effective international control."

Anti-Ballistic Missile Treaty (ABM) (1972)
To prevent the continuing build up of the number of nuclear warheads and delivery systems during the Cold War, this treaty prohibited the deployment of significant strategic defenses. This way the United States and the Soviet Union assured the other side the effectiveness of their nuclear deterrence. This is known as Mutual Assured Destruction (MAD). This treaty is of great importance and has become the cornerstone for the following nuclear arms control treaties between both countries; but it is has been labeled "outdated" by the current administration. The proposed National Missile Defense (NMD) system would violate the ABM Treaty, therefore—unless Russia agrees to modify the treaty—it would be abrogated (with 6 months notice) or become invalid through violation by the US.

Strategic Arms Limitation Treaty I (SALT I) (Entered into force 1972)
The Treaty and Interim Agreement limit the number of ABM's to 200 at 2 sites for each country, and limit offensive ballistic missiles to 1,710 for the United States and 2,347 for the Soviet Union.

Threshold Test Ban Treaty (1974)
One hundred seventeen nations are parties to the "Treaty on the Limitation of Underground Nuclear Weapon Tests." The TTBT establishes a nuclear "threshold," by prohibiting tests having a yield exceeding 150 kilotons (equivalent to 150,000 tons of TNT). The threshold is militarily important since it removes the possibility of testing new or existing nuclear weapons with very high yields.

SALT II (1979):
SALT II Limited different kinds of strategic weapons and weapons systems. It was signed by both countries, but not ratified by the US Senate, and hence never entered into force. Nevertheless, both countries adhered to the limits until exceeded by the US under President Reagan.

Intermediate Nuclear Forces Treaty (INF) (Entered into force 1988):
In the 1980s, both the United States and Soviet Union "forward deployed" intermediate-range nuclear weapons in Europe and western Russia, creating a hairtrigger situation. The INF eliminated intermediate range and short range missiles and established an onsite inspection regime in Europe.

Strategic Arms Reduction Treaty I (START I) (signed 1991, ratified by the US Senate in 1992): Phased reduction and limitation of strategic nuclear warheads to 6,000 deployed on each side. This is the force limit status today.

START II (signed by Russia and US 1993; approved by Senate 1994, by the Russian Duma April 2000, but needs to go back to US Senate for approval of amendments before it can enter into force).
Goal: reduction of deployed strategic nuclear warheads to below 3,500 for each side.

The US-Russian START III framework agreement envisions reductions to no more then 1,000 warheads on each side.

Comprehensive Nuclear Test Ban Treaty (CTBT) (multilateral treaty, signed by US 1996, ratification rejected by US Senate 1999)
The CTBT signing ceremony in 1996 was the culmination of decades of on and off negotiations toward this treaty. The CTBT commits the signatory countries to refrain from testing nuclear weapons or other nuclear devices, or encourage or cause other parties to do so. The CTBT establishes an elaborate verification system, including seismic monitoring stations and on-site inspections. 161 countries have signed, 77 have ratified the treaty. The 44 known or potential nuclear weapons states are required to ratify before the treaty can enter into force; 31 have done so, including Russia (the US, China, India, Pakistan, North Korea and Israel are required but have not ratified). Though President Clinton was the first to sign the CTBT in 1996, the US Senate voted in 1999 against CTBT ratification. (Senate ratification requires a 2/3 majority) Since the initial signing ceremony in 1996, all nations except India and Pakistan have exercised a voluntary moratorium on nuclear weapons tests.

Despite the fact that the United States failed to ratify the CTBT, other "states party to the treaty" have put considerable effort into preparing for its entry-into-force, including meetings to establish the international monitoring regime. Future reassessment by the US Senate appears likely.

Nuclear Weapons Convention (NWC) (United Nations Discussion Draft, submitted by Costa Rica to the UN Secretary General in 1997)

The NWC is currently a draft model treaty for the phased elimination of nuclear weapons. This is a model of the sort of legislation that will lead to nuclear weapons abolition.

The NWC in its current form prohibits development, testing, production, stockpiling, transfer, use and threat of use of nuclear weapons. States possessing nuclear weapons will be required to destroy their arsenals according to a series of phases. The Convention also prohibits the production of weapons usable fissile material and requires delivery vehicles to be destroyed or converted to make them non-nuclear capable.

The model NWC was drafted by representatives from 13 NGOs including PSR's parent organization, International Physicians for the Prevention of Nuclear War. The text of the Model NWC is available at

Wolfgang Kluge, MD and Martin Fleck, July, 2001

Related Links:
Arms Control Association
Coalition to Reduce Nuclear Dangers
US State Department Bureau of Arms Control, Treaties and Agreements 

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