Key Arms Control and Disarmament Treaties and Their Impact

Since the world entered the nuclear age in 1945, governments have signed dozens of treaties to slow the arms race and reduce the risk of catastrophe. These agreements form the backbone of what we call arms control and disarmament. Arms control aims to regulate and limit how weapons are developed, deployed, and tested, while disarmament goes further to eliminate weapons entirely. Understanding these treaties is essential for anyone studying peace and conflict, because they reveal both how far cooperation can stretch and where it tends to break down. This post walks through the most important agreements, what they achieved, and why some of them are now under serious strain.

Why arms control treaties became necessary 🔗

The destruction of Hiroshima and Nagasaki in 1945 demonstrated a new category of weapon, one capable of ending entire cities in seconds. Within years, the United States and the Soviet Union began building large arsenals, and the fear of mutual destruction pushed both sides toward negotiation. According to the United Nations, more than 2,000 nuclear weapon tests were conducted between 1945 and 1996, many far more powerful than the Hiroshima bomb. This testing contaminated the environment and accelerated the arms race, creating strong incentives to negotiate limits.

The earliest treaties did not try to abolish weapons. Instead, they focused on keeping certain regions and environments weapon-free, a more achievable goal during the tense early Cold War. This step-by-step logic, starting with limited measures and building toward larger ones, has shaped arms control ever since.

The early treaties: keeping weapons out of new frontiers 🔗

The Antarctic Treaty (1959) 🔗

The Antarctic Treaty, signed in 1959 and entering into force in 1961, was a landmark first step. It demilitarized an entire continent. The treaty prohibits military maneuvers, weapon tests, the building of military installations, and the disposal of radioactive waste in Antarctica. Its real significance was conceptual. It became the first treaty to put the idea of a nuclear-weapon-free zone into practice, a model later applied to Latin America, the South Pacific, the seabed, and outer space.

The Partial Test Ban Treaty (1963) 🔗

The Partial Test Ban Treaty (PTBT), also called the Limited Test Ban Treaty, was signed in Moscow in August 1963 by the United States, the Soviet Union, and the United Kingdom. It prohibits nuclear weapon tests in the atmosphere, in outer space, and under water. It did not ban underground testing, but it stopped explosions that would spread radioactive debris beyond a state’s borders. The motivation was partly environmental and partly political, since the Cuban Missile Crisis of 1962 had shown how close the superpowers had come to disaster.

It is worth noting that India played an early role here. In 1954, India made the first proposal calling for an agreement to ban nuclear weapons tests. This early advocacy reflects a consistent theme in Indian foreign policy: support for genuine, universal disarmament rather than partial measures.

The Outer Space Treaty (1967) 🔗

Building directly on the Antarctic model, the Outer Space Treaty extended the same principle to space. It bans placing nuclear weapons or other weapons of mass destruction in orbit, on the Moon, or on any celestial body, and prohibits using the Moon for military purposes. As space becomes more crowded with satellites and competing national programs, this treaty remains highly relevant today.

The Non-Proliferation Treaty: the cornerstone agreement 🔗

The Treaty on the Non-Proliferation of Nuclear Weapons (NPT) is widely considered the most important arms control agreement ever signed. It was opened for signature in 1968 and entered into force in 1970. Today, 190 countries are party to the NPT, making it the most widely adhered-to arms control agreement in the world.

The three pillars 🔗

The NPT rests on three commitments. Non-proliferation: nuclear-weapon states agree not to help others acquire nuclear weapons, and non-nuclear states agree not to develop them. Disarmament: all parties pledge to pursue good-faith negotiations toward ending the arms race and achieving complete disarmament. Peaceful use: every party has the right to access nuclear technology for civilian purposes, under safeguards monitored by the International Atomic Energy Agency.

The treaty recognizes exactly five nuclear-weapon states: the United States, Russia, the United Kingdom, France, and China. These are the countries that tested a nuclear device before January 1, 1967.

Why India never signed 🔗

This is a crucial point for students. India has consistently refused to sign the NPT, viewing it as discriminatory because it perpetuates a hierarchy of nuclear-armed and non-nuclear-armed states. The objection is principled: the treaty permanently divides the world into nuclear “haves” and “have-nots” based on an arbitrary cut-off date, while imposing no firm timeline on the recognized powers to actually disarm.

India tested its first nuclear device in 1974 and conducted further tests in 1998, becoming a nuclear power outside the NPT framework. Staying outside the treaty came at a cost, including limited access to global nuclear trade for many years. That changed somewhat with the 2006 Indo-US civil nuclear deal, which allowed nuclear cooperation under specific safeguards. India today maintains a policy of credible minimum deterrence and a declared No First Use posture.

Reducing the superpower arsenals: START 🔗

While the NPT focused on stopping the spread of weapons, a separate track of bilateral treaties between the United States and the Soviet Union (later Russia) aimed at actually reducing the two enormous existing arsenals. The Strategic Arms Reduction Treaty, or START, was the key instrument here.

These treaties mattered because the two superpowers together held the overwhelming majority of the world’s warheads. The global stockpile fell from a high of around 70,000 warheads in the mid-1980s to roughly 12,000 today, and the START process was central to that decline.

New START and its expiration 🔗

The most recent agreement in this lineage was New START, signed in 2010 by the United States and Russia. It capped each side at 1,550 deployed strategic nuclear warheads, 700 deployed delivery vehicles, and 800 deployed and non-deployed launchers. Critically, it included an intrusive verification regime with on-site inspections and regular data exchanges, allowing each country to confirm the other was complying.

Here is the most important recent development for students to know. New START was extended once in 2021 and was always set to end in 2026. It lapsed on February 5, 2026, and no replacement agreement was in place. For the first time in decades, there are no negotiated caps on the long-range nuclear forces of the two largest nuclear powers. As of early 2026, the Nuclear Non-Proliferation Treaty remains the only legally binding mechanism restraining nuclear weapons globally. This makes the NPT’s continued health more important than ever.

The Comprehensive Test Ban Treaty (1996) 🔗

The Comprehensive Nuclear-Test-Ban Treaty (CTBT), adopted in 1996, sought to finish what the Partial Test Ban Treaty started. While the PTBT left underground testing legal, the CTBT bans all nuclear explosions in every environment, including underground. To enforce this, it established a global network of monitoring stations run by an organization in Vienna that detects nuclear explosions through seismic, hydroacoustic, and other sensors.

Why the CTBT is not yet in force 🔗

Despite being adopted nearly three decades ago, the CTBT has still not entered into force, because a specific list of nuclear-capable states must ratify it first, and several have not. India is among them. India views the CTBT as flawed for the same reason it rejects the NPT. It argues the treaty should be linked to a time-bound commitment by nuclear weapon states to actually eliminate their arsenals, and without that commitment, a test ban simply locks in the existing power structure. India has, however, maintained a voluntary moratorium on nuclear testing since 1998.

The verification problem: why treaties succeed or fail 🔗

Across all these agreements, one factor consistently determines success: verification. A treaty is only as strong as the ability of each party to confirm the others are keeping their word. The CTBT’s monitoring network and New START’s on-site inspections were both attempts to solve this trust problem.

When verification breaks down, treaties weaken. Russia suspended its participation in parts of New START’s verification regime between 2023 and 2026, citing tensions over Ukraine, which meant the United States could no longer fully confirm Russian compliance. This erosion of trust contributed to the treaty being allowed to lapse. The lesson for peace studies is clear: agreements need not only good intentions but robust, mutual inspection mechanisms to survive periods of geopolitical stress.

What these treaties achieved, and where they fall short 🔗

Taken together, these agreements produced real results. They kept Antarctica and outer space free of weapons, ended atmospheric testing that was poisoning the environment, slowed the spread of nuclear weapons to new countries, and cut superpower arsenals dramatically. The fact that only nine countries possess nuclear weapons today, rather than the dozens once predicted, is partly a testament to the NPT.

Yet the limits are equally visible. The recognized powers have never fully disarmed as the NPT envisioned. Key treaties like the CTBT remain stuck outside force. Verification regimes can collapse, as New START’s recent expiration shows. And countries like India have always argued that a system dividing the world into permanent nuclear haves and have-nots cannot deliver genuine, lasting security. The arms control framework built since 1945 is real and valuable, but it is also fragile and incomplete.

What do you think? Should disarmament treaties demand a firm, time-bound commitment from existing nuclear powers to eliminate their weapons, as India has long argued, or is the gradual step-by-step approach more realistic? And with New START now expired, what mechanisms could realistically replace it to keep the world’s two largest arsenals in check?

References

1. https://www.un.org/en/peaceandsecurity/disarmament-numbers
2. https://www.nationsencyclopedia.com/United-Nations/Arms-Regulation-and-Disarmament-MAIN-ACHIEVEMENTS.html
3. https://2009-2017.state.gov/t/avc/trty/199116.htm
4. https://www.nti.org/education-center/treaties-and-regimes/treaty-banning-nuclear-test-atmosphere-outer-space-and-under-water-partial-test-ban-treaty-ptbt/
5. https://www.atomicarchive.com/resources/treaties/outer-space.html
6. https://www.cfr.org/articles/us-russia-nuclear-arms-control
7. https://www.studyiq.com/articles/non-proliferation-of-nuclear-weapons-npt/
8. https://civilservicepala.org/daily-gk-alerts/india-and-the-nuclear-non-proliferation-treaty-npt-a-balanced-overview
9. https://www.nti.org/analysis/articles/the-end-of-new-start-from-limits-to-looming-risks/
10. https://www.state.gov/new-start-treaty
11. https://www.brookings.edu/articles/what-comes-after-new-start/
12. https://www.cfr.org/articles/nukes-without-limits-a-new-era-after-the-end-of-new-start
13. https://www.nti.org/analysis/articles/india-nuclear-disarmament/
14. https://www.congress.gov/crs-product/IF12964