Acknowledged Nuclear Powers

Before the breakup of the Soviet Union, there were five acknowledged nuclear weapons states: the U.S., the USSR, France, England, and China. The latter three had all tested nuclear weapons. France and England had several hundred nuclear warheads each, and both had developed plans in the late 1980s to increase their arsenals to about 1500 each. India had set off one nuclear explosion in the atmosphere, in 1974. It claimed that it was interested in nuclear explosives only for peaceful purposes, and it had not followed this explosion with any other testing, or with deployment of weapons; so India was generally not considered a nuclear weapons state.

The Non-Proliferation Treaty

The most important international measure against further proliferation of nuclear weapons has been the "Treaty on the Non-Proliferation of Nuclear Weapons", (NPT) which entered into force in 1970. The treaty has the unusual property of dividing its signers into two classes: those states that did not have nuclear weapons at the time of signing committed themselves not to develop, or make efforts to obtain nuclear weapons. Those states that did have nuclear weapons committed themselves to (a) helping the non-nuclear states to use nuclear technology for peaceful purposes, and (b) working toward reductions in their nuclear arsenals and reduction in international tensions.


There was also a system for monitoring compliance with the NPT. An organization called the International Atomic Energy Authority (IAEA) was set up to verify that when non-nuclear states received civilian nuclear facilities (generally this meant reactors) they would not divert nuclear materials to weapons uses. The IAEA sends teams of scientists and technicians to these facilities. Among other things, they measure the amount of plutonium and other radioactive materials produced, and document where it goes.


There are two types of IAEA inspections: (1) inspections of declared sites -- sites which the target nation reveals, and declares to be permitted facilities under the NPT; (2) inspections on demand -- inspections of sites which the target nation has not revealed, but which the IAEA has reason to consider suspect, or in violation of the treaty. The IAEA cannot randomly inspect technical facilities throughout a nation, but can sometimes act on information supplied by intelligence services of other nations -- often images of large building complexes revealed in satellite photographs.

History of the NPT

The Non-Proliferation Treaty has had a rocky history, as one might have expected. A number of important nations did not sign it originally, notably France, India, Israel, North Korea, Pakistan and South Africa. Many non-nuclear nations (both signers and non-signers) objected to the discriminatory nature of the treaty. It is not only that some nations are "allowed" to have nuclear weapons and others are not, but the nuclear states are not required to have IAEA inspections of their nuclear facilities, while the non-nuclear states are so required. Many argued that the nuclear states were not living up to their commitment to reduce their nuclear arsenals. Indeed, until the Intermediate-range Nuclear Force agreement in 1987, there were no reductions in nuclear weapons at all -- although there were several treaties that controlled the growth of the arsenals. The START treaties, signed after the breakup of the Soviet Union, do mandate reductions, which have taken place.

Link to nuclear testing

The non-nuclear states also argued that underground testing of nuclear weapons should be discontinued and banned by treaty, as evidence that the nuclear states were serious about de-emphasizing the nuclear card in international relations.

Despite these controversies, the NPT was extended indefinitely at a 1995 review conference.

Rating the NPT

In a number of important ways, discussed more below, the NPT has not been successful. One should remember, however, that in 1960 President Kennedy wrote that he expected that 20 nations would have nuclear weapons by the end of the 1960s. He considered this the gravest threat to world peace, and so he set in motion the discussions that culminated in the NPT, a few years after his death. With 40 years hindsight, it is clear that proliferation has not occurred at the pace that Kennedy expected, and some of the credit for that belongs to the NPT.

India and Pakistan

Impetus in India for building a nuclear arsenal began following its loss of a border war with China. India's leaders have also felt that a nuclear capability gave it status as a world power. Using reactors originally supplied by France and Canada, and its own reprocessing facilities, India has built between 50 and 100 atomic weapons. Pakistan began work on a nuclear arsenal in the 1980s, and is estimated now to have between 20 and 40 nuclear weapons. Pakistanis felt the need to counter India's substantial superiority in conventional weapons.

Nuclear Tests in 1998


The nuclear risk in the Indian-subcontinent was heightened because of
  • nuclear tests carried out by both countries in 1998
  • flaring up of the dispute over Kashmir in 1999
  • introduction of missiles, which can reach the other country in less than 5 minutes
  • threatening talk on both sides

More recently, statesmen in both countries have made an effort to reduce tensions, including beginning negotiations on Kashmir.

It is difficult to say how the war against terrorism will play in the Indian sub-continent,, but it is widely believed in India that it is the target of Islamic extremists based in Pakistan.


From the beginning of the nuclear age, Israel was considered a likely candidate for development of nuclear weapons, (1) because of the high level of its scientific and technical personnel, and (2) because of its precarious position surrounded by hostile neighbors. A reactor in the Negev at Dimona was recognized in the 1960s to be the same type used by the U.S. to produce plutonium for weapons. Reprocessing facilities also exist at Dimona. By the late sixties, it was generally believed that Israel had at least one bomb.

In 1986, Mordechai Vanunu, a former technician at Dimona, reported that Israel had built up to 200 weapons, including some employing nuclear fusion. American experts who interviewed Vanunu considered his report reliable.

Weapons without testing

Early in the nuclear period, it was believed that a nation would have to carry out some tests of a nuclear device before it could have any confidence about using the device as a weapon. This was important, because tests could not be carried out in secrecy, and so the international community could at least know for certain whether a given nation had nuclear weapons. As time has gone on, however, the technology of building these weapons has become sufficiently refined, so that testing may not be required to build an arsenal. Thus, most experts believe that Israel has a reliable arsenal.


Iraq was a signatory to the NPT. The degree of progress toward a nuclear weapon capability that was made by Iraq during the years prior to the 1990 Persian Gulf War revealed inadequacy in the treaty's provisions. In 1981, Israel bombed and destroyed the Osirak reactor at Tuwaitha in Iraq, claiming that it was designed to produced plutonium for nuclear weapons. Iraq then switched from plutonium to uranium, and sought to obtain equipment for separating uranium isotopes.

The Iraqis investigated every separation method, and pursued both electromagnetic separation and centrifuges. Suppliers of centrifuges included companies in Germany, the U.S., Japan, and Switzerland. Most equipment reached Iraq through intermediaries; the manufacturing company does not necessarily know who the eventual customer is.

Export Controls

Most of the industrialized nations have some controls on export of materials that can be used for making nuclear weapons. These controls have not always worked well, (1) because of transmission through intermediaries, and (2) because many kinds of technical equipment are "dual-use", that is, they can be used for civilian as well as for military purposes.

Iraq continued

The U.S., embarking on war in Iraq in 2003, claimed that Iraq was actively pursuing nuclear (as well chemical and biological) weapons. Investigations since the end of large-scale fighting found no evidence of this threat.


North Korea long felt threatened by American nuclear weapons deployed in South Korea following the Korean War. These American weapons were removed during the thaw accompanying the demise of the Soviet Union. In 1994 the U.S. and North Korea signed an agreement in which North Korea agreed to freeze its nuclear weapons development program, in particular a nuclear reactor that was capable of producing plutonium. In exchange, the U.S. offered economic aid, including several nuclear reactors designed for producing electricity.

By 2002, however, it became apparent that North Korea had violated the 1994 agreement. Although it had discontinued production of plutonium, it had secretly continued its program to build nuclear weapons, now using enriched uranium as fissile material. Despite U.S. pressure to stop its nuclear program, and given relatively weak pressure from Russia and China, North Korea exploded a small atomic bomb in 2006.


Early in 2003 Iran revealed that it was much closer to establishing a supply of enriched uranium than outside experts had previously thought. Iran is employing centrifuge technology, which is capable of producing either highly enriched uranium for nuclear explosives or "low-enriched uranium" (3% to 5% 235U) for power reactors. What is not widely known is that it takes more processing to enrich from natural uranium (0.7%) to 5%, than to enrich from 5% to 90%; i.e. a nation that can produce low-enriched uranium has gone a long way toward producing weapons-grade uranium.

A "Sunni" bomb?

Iran claims that its intention is only to build reactors and that it adheres to the Non-Proliferation Treaty. Given that Iran is an oil-rich nation, it seems unlikely that it has a great need for nuclear energy. In the U.S. most of the concern about an Iranian bomb has focussed on the threat to Israel. But some analysts see a bigger risk in the Sunni-Shia conflict. That is, Saudi Arabia (Sunni) and Iran (Shia) compete for influence in the Arab region, and a nuclear Iran will be viewed as a threat to Saudi Arabia, which may then try to enter the nuclear club also. Although Saudi Arabia does not have a strong national technological base, it does have close ties to Pakistan which might help it to obtain the bomb.

Brazil and Argentina

A potential nuclear arms race between Brazil and Argentina was averted through the efforts of scientists in both nations. In 1991 it was discovered that military officials in Brazil had established a nuclear weapons development project, which was unknown to the civilian government. This project was disbanded, and the two countries signed a treaty renouncing the development or use of nuclear weapons.

South Africa


South Africa had secretly developed a nuclear weapon, but then announced that it was abandoning its nuclear program. It then signed the NPT in 1991.

Late in 2003 Libya announced that it was discontinuing what had been an active effort to build a nuclear weapon. It agreed to international inspections to verify its compliance with the Non-proliferation Treaty. Evidence suggests that Libya's program was aided by Pakistani nuclear scientists, although not necessarily by the Pakistani government.


  • Nuclear status of:
    • U.S., Russia
    • England, France, China
    • Israel, Iran, Iraq
    • India, Pakistan
    • North Korea
  • Weapons without testing
  • The Non-proliferation Treaty
  • The IAEA, inspections
  • Export controls: Why they don't always work