The History of the Nuclear Non-Proliferation Regime

Nuclear weapons have shaped global security since the atomic bombings of Hiroshima and Nagasaki in 1945. They can destroy cities, contaminate territory, and make even limited military crises politically existential. The nuclear non-proliferation regime is the legal and diplomatic system that tries to stop new nuclear arsenals, monitor civilian nuclear technology, and press nuclear-armed states toward disarmament. Its institutional core began with the International Atomic Energy Agency (IAEA) in 1957 and the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in 1968. The regime has limited the number of recognized nuclear-weapon states, but it has not removed nuclear deterrence from international politics.

The beginning of the regime

In the wake of the atomic bombings of Hiroshima and Nagasaki, the world quickly realized the destructive potential of nuclear weapons. This led to increased calls for regulation and control. In 1953, U.S. President Dwight D. Eisenhower proposed the creation of a United Nations agency focused on controlling nuclear technology while promoting the benefits of its peaceful uses. Following his proposal, the International Atomic Energy Agency (IAEA) was established in 1957, with its headquarters in Vienna. The IAEA was designed to promote peaceful nuclear energy and ensure that nuclear technology was not diverted to nuclear weapons production. Since then, it has played a crucial role in monitoring nuclear programs and facilitating technical cooperation among countries.

The journey towards a formal non-proliferation treaty began more decisively in 1961, when the United Nations General Assembly passed Resolution 1665, proposed by Ireland. The resolution called for all states to negotiate a treaty that would prevent non-nuclear-armed states from acquiring nuclear weapons.

The urgency of controlling nuclear arms was further underscored by the Cuban Missile Crisis in 1962, which brought the world perilously close to nuclear war. Soviet warheads were installed in Cuban soil, and the United States engaged in a naval blockade so as to buy time while it negotiated the removal of the missiles with the Soviet Union. Thankfully, those states concluded a secret agreement, according to which Cuba would lose the warheads, but American missiles in Turkey and Italy were to be removed too. Following this crisis, the United States and the Soviet Union began to engage more seriously in negotiations to control nuclear weapons, focusing on two types of non-proliferation:

• Horizontal non-proliferation seeks to block additional countries and non-state actors from acquiring nuclear weapons.
• Vertical non-proliferation seeks to cap or reduce the arsenals of countries that already possess nuclear weapons.

In 1963, the United States, the Soviet Union, and the United Kingdom initially signed the Partial Nuclear-Test-Ban Treaty (PTBT). This treaty prohibited nuclear tests in the atmosphere, underwater, and in space. It restricted testing to underground settings in the hope of limiting further development and refinement of nuclear weapons. However, the PTBT lacked a mechanism for international monitoring, and this oversight limited its effectiveness.

The Non-Proliferation Treaty

Finally, in 1968, the nuclear non-proliferation regime progressed significantly, due to the adoption of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). This treaty came into force in 1970 and became the cornerstone of the regime. It was based on three pillars:

1. Non-proliferation (articles I and II): Nuclear weapon states, defined as those who had tested nuclear weapons before January 1, 1967, agreed not to transfer nuclear weapons or other explosive devices, and non-nuclear-weapon states agreed not to seek to develop or acquire such devices. In practical terms, only the five permanent members of the United Nations Security Council were authorized to have nuclear weapons: the United States, the United Kingdom, France, Russia and China.
2. Article VI makes disarmament a treaty obligation rather than a voluntary political promise. Nuclear-weapon states committed to pursuing negotiations in good faith towards nuclear disarmament and, eventually, general and complete disarmament.
3. Peaceful use of nuclear technology (article IV): All states were entitled to participate in the exchange of scientific and technological information to further the peaceful uses of nuclear energy.

According to Article III of the NPT, non-nuclear-armed states are required to sign safeguard agreements with the IAEA to ensure compliance with their non-proliferation commitments. The IAEA inspects the circulation and use of nuclear materials. These safeguards help prevent civilian nuclear programs from becoming nuclear weapons programs.

Despite the broad adoption of the NPT (with notable exceptions like India, Pakistan, Israel and South Sudan), challenges remain. North Korea, for instance, withdrew from the treaty in 2003. Since then, it has defied the non-proliferation regime through successive nuclear tests.

The Regime at the Height of the Cold War

During the 1970s, there emerged a period of détente in the Cold War, in which easing tensions led to significant treaties between the United States and the Soviet Union aimed at limiting nuclear arsenals and delivery systems. Cold War arms control built rules around the delivery systems that made deterrence most unstable. Notable among these was the 1972 Anti-Ballistic Missile Treaty, which restricted the use of missile defense systems that could intercept incoming ballistic missiles. That same year, the Strategic Arms Limitation Talks (SALT I) resulted in further agreements to limit both intercontinental and submarine-launched ballistic missiles. This phase of negotiation continued with the Threshold Test Ban Treaty (TTBT) in 1974, which curtailed nuclear tests to under 150 kilotons to inhibit the development of more sophisticated nuclear weapons.

However, the 1980s witnessed a resurgence of Cold War tensions, briefly stalling progress in arms control. This changed in 1987 with the Intermediate-Range Nuclear Forces (INF) Treaty, which eliminated all land-based ballistic and cruise missiles with ranges of 500 to 5,500 kilometers. This treaty significantly affected the security landscape of Europe, because the continent would no longer be threatened by Soviet nuclear missiles. In the same year, the G7 countries initiated the Missile Technology Control Regime (MTCR). The MTCR is an informal and voluntary partnership aimed at preventing the proliferation of missiles capable of carrying significant payloads, including weapons of mass destruction. At first, it focused on nuclear-capable missiles. Later, it expanded to unmanned aerial vehicles and other delivery systems, and now involves more than 30 countries.

The Regime at the Turn of the Century

The 1990s opened new opportunities for nuclear non-proliferation in the post-Cold War environment. The post-Cold War bargain depended on keeping non-proliferation and disarmament politically linked. The 1995 NPT Review Conference not only extended the Nuclear Non-Proliferation Treaty indefinitely but also proposed the creation of a nuclear-weapon-free zone in the Middle East. Although these efforts faced setbacks, particularly after the assassination of Israeli Prime Minister Yitzhak Rabin, they marked a significant attempt at regional disarmament. Another critical development was the Comprehensive Nuclear-Test-Ban Treaty in 1996, which sought to ban all nuclear explosions. However, this treaty has yet to enter into force due to the lack of ratification by key nations. The revelation of clandestine nuclear activities in North Korea and Iraq prompted the 1997 approval of an additional protocol to the IAEA Safeguards Agreement, enhancing the agency’s ability to inspect and verify nuclear programs.

Legal and advisory challenges also emerged, most notably through a 1996 advisory opinion by the International Court of Justice (ICJ). According to the Court, the legality of the use of nuclear weapons could not be ruled out and would need to be analyzed on a case-by-case basis. Even so, the judges were adamant that international humanitarian law had to be upheld in any circumstance, as long as the survival of a state is not threatened.

In 2000, the Sixth Review Conference of the NPT marked a significant advancement in nuclear disarmament efforts. During this conference, a document titled the “13 Practical Steps on Nonproliferation and Disarmament” was adopted. This document laid out specific guidelines aimed at implementing Article VI of the NPT, focused on the disarmament of nuclear-armed states. The approval of these steps was largely driven by the pressure exerted by the New Agenda Coalition (NAC), a group of non-nuclear middle-power countries. These nations argued against the indefinite extension of the NPT on the grounds that nuclear-armed states were not fulfilling their disarmament obligations as outlined in Article VI. The Coalition advocated for the total elimination of nuclear arsenals and the assurance that such weapons would never be produced again.

However, from 2000 onwards, there were noticeable failures in subsequent NPT Review Conferences. It wasn’t until 2017 that another significant breakthrough occurred due to negotiations under the auspices of the United Nations.

The TPNW and Recent Developments

In 2017, there was the conclusion of the negotiations for the Treaty on the Prohibition of Nuclear Weapons (TPNW). This treaty emerged from discussions prompted by the Humanitarian Initiative, a group of states that held conferences about nuclear weapons in 2013 and 2014. This group highlighted the catastrophic humanitarian, environmental, and economic consequences of accidental or intentional nuclear detonations, and vowed to “fill the legal gap for the prohibition and elimination of nuclear weapons”. The TPNW changed the legal vocabulary of abolition while nuclear-armed states stayed outside its prohibition model.

Another major force behind the TPNW was the International Campaign to Abolish Nuclear Weapons (ICAN), a coalition of civil society organizations that played a crucial role in the international conference that negotiated the treaty. In recognition of its efforts, ICAN was awarded the Nobel Peace Prize in 2017.

However, no significant nuclear powers or NATO members joined the TPNW. For example, the Netherlands was the only NATO country that participated in the TPNW negotiations but voted against the treaty. Other countries did not vote at all, even abstaining from the preliminary discussions at the United Nations. These actors argue that a gradual prohibition of nuclear weapons is preferable, as an immediate ban could undermine their nuclear deterrence policies.

Nevertheless, the TPNW entered into force in 2021 after being ratified by 50 states. Its efficacy is limited by the absence of the five NPT-recognized nuclear-weapon states and the nuclear-armed states outside the NPT. On January 3, 2022, the five NPT nuclear-weapon states issued a joint statement on preventing nuclear war and avoiding arms races, affirming that a nuclear war cannot be won and must never be fought. The statement reaffirmed risk reduction and existing NPT obligations while leaving the TPNW’s prohibition model outside their policies.

That distance was visible again at the 2026 NPT Review Conference. According to the United Nations, the conference ended on May 22, 2026 without consensus on a final declaration, the third consecutive failed review-cycle outcome. Current Federation of American Scientists estimates for the beginning of 2026 put Russia at about 5,420 total warheads and the United States at about 5,042, with China at about 620. India, Pakistan, Israel, and North Korea have smaller arsenals, but several of these stockpiles are assessed as growing. The regime therefore still limits formal nuclear status more effectively than it compels existing nuclear-armed states to reduce their arsenals.

Conclusion

The nuclear non-proliferation regime limits access to nuclear weapons by combining treaty obligations, IAEA safeguards, export controls, review conferences, and political pressure. It also protects civilian nuclear cooperation by giving states a monitored channel for peaceful uses of nuclear technology. Its main weakness is the unresolved bargain at the center of the NPT: non-nuclear-weapon states accept permanent restrictions, while nuclear-weapon states face a disarmament obligation that depends on diplomacy, verification, and political will. As arsenals are modernized and review conferences fail to produce consensus, the regime remains indispensable but incomplete.