Explainer: US nuclear re‑test could ignite global arms race; the world watches

A decision by the US to restart testing of nuclear weapons after a 33‑year hiatus signals multiple implications across the world. It indicates a shift away from the era of ‘reducing nuclear weapons’ and could trigger a fresh arms race.

US President Donald Trump has directed the US Department of War to restart testing and justified the move, citing the need to “start testing our Nuclear Weapons on an equal footing” with rival nations Russia and China, who have been enhancing their nuclear capabilities, although neither has tested nuclear explosives since the early 1990s.

Trump’s move appears to have been triggered by an announcement made by Russian President Vladimir Putin on the successful test of a unique underwater long‑range drone named ‘Poseidon’. The drone, which can carry a nuclear weapon, is intended to strike coastal targets by triggering tsunamis and destroying port and shore‑based crude‑oil‑refining infrastructure. The Russian Poseidon is a nuclear‑powered, autonomous underwater drone that operates like a torpedo, designed as a strategic nuclear weapon. It has virtually unlimited range because of its nuclear propulsion system.

However, the of test of the ‘Poseidon’ by Moscow did not entail a nuclear explosion.

Threat of an arms race

Geopolitically, the US decision risks igniting a fresh nuclear arms race. Russia and China or even others — India, Pakistan and Iran — could respond with their own testing or accelerate development of new nuke-capable weapons. The existing arms‑control frameworks, such as the Comprehensive Nuclear‑Test‑Ban Treaty (CTBT), to which the US is a signatory but has not ratified, are already looking fragile with Trump’s move.

The move also complicates decades of diplomatic efforts towards nuclear disarmament and arms reduction.

International think-tank Sweden-based Stockholm International Peace Research Institute (SIPRI) had warned of nuclear arms race in its report ‘Armaments, Disarmament and International Security’ released in June this year.

The SIPRI said, “The signs are that a new qualitative nuclear arms race is gearing up and, compared with the last one, the risks are likely to be more diverse and more serious. Among the key points of competition will be technological capacities in cyberspace, outer space and ocean. The bilateral nuclear arms control between Russia and the US entered a crisis some years ago and is now almost over.”

It had warned and added “nearly all of the nine nuclear-armed countries — the US, Russia, UK, France, China, India, Pakistan, North Korea and Israel — continued intensive nuclear modernisation programmes in 2024, upgrading existing weapons and adding newer versions”.

The report is the annual assessment of the state of armaments, disarmament and international security.

From a US perspective, restarting nuclear testing is aimed at ensuring the reliability, safety and modernisation of the US nuclear arsenal — an important national deterrence factor. This step is intended to demonstrate US resolve and technological edge in maintaining a credible deterrent amid rising global tensions and renewed nuclear competition.

Physical tests not needed

An argument is that in today’s world there is no immediate technical need for explosive testing, computer simulations and previous data can mimic a test.

Environmentally, the resumption of nuclear explosive tests raises serious concerns about radioactive contamination and public health risks, particularly in the Nevada desert in the US, where tests would be conducted. Past nuclear testing caused lasting environmental damage and displaced communities.

Nuclear testing causes significant environmental harm with long-lasting and wide-ranging impacts. Nuclear explosions release large amounts of radioactive isotopes into the air, water and soil. These radionuclides can persist in the environment for decades or longer, contaminating ecosystems. Fallout spreads radioactive dust and particles over large areas, which can enter the food chain through crops, animals, and water supplies, posing health risks to humans and wildlife.

Timing of Trump’s announcement proves crucial

Trump’s announcement comes at a time when Arms control negotiations are at a critical crossroads. The most prominent existing treaty, the New Strategic Arms Reduction Treaty (New START) between the United States and Russia, is set to expire on February 4, 2026. This treaty limits the number of deployed strategic nuclear warheads and delivery systems, providing transparency and a framework for arms reduction between the two largest nuclear powers. Negotiations to replace or extend New START face multiple challenges. Russia suspended its participation in the treaty in 2023.

The US wants any future agreement under the New START Treaty to include China — reflecting concerns over China’s expanding nuclear capabilities and the need for a trilateral framework — but China has so far resisted such inclusion.