Just Say No to Nuclear Testing

US President Donald Trump threw yet another curveball at international norms when, in response to “other countries’” nuclear testing programs, he instructed the US Department of Defense “to start testing our Nuclear Weapons on an equal basis”.

This instruction, revealed in an October 29 social media post, is potentially the president’s most destabilizing intervention to date. It could erode the normative moratorium on testing—a key remaining pillar of post-Cold War nuclear détente—and dial up already heated great-power frictions.

Ambiguity Reigns

It was not clear what specific testing parameters Trump meant by his obtuse instruction, and perhaps he was deliberately ambiguous. When US Secretary of Energy Chris Wright sought to constrain the scope of possible US action, stating on November 2, “I think the tests we’re talking about right now are system tests. These are not nuclear explosions, these are what we call noncritical explosions,” Trump doubled down. He told 60 Minutes, “We’re going to test nuclear weapons like other countries do,” naming Russia, China, and North Korea. Trump also explained, “You have to see how they work … and … I don’t want to be the only country that doesn’t test.”

Interpreting a Rationale

Despite the imprecision of Trump’s remarks, there seem to be two primary motivations for his instruction.

The first is that US adversaries are conducting tests in contravention of treaty-level obligations and norms. For the United States and Russia, these obligations arise bilaterally under the Threshold Test Ban Treaty (TTBT), which prohibits underground nuclear tests with a yield exceeding 150 kilotons, and the multilateral Comprehensive Test Ban Treaty(CTBT), which seeks to ban all nuclear test explosions. The United States, Russia, and China are CTBT signatories and, while they do not have ratification status, are ostensibly committed to its object and purpose. None of these countries has carried out a full-scale test since the 1990s, and of all other states, only North Korea has breached the moratorium and tested in this century.

There are, however, reasons for concern that Russia and China might be conducting tests that exceed established parameters and/or notification requirements.

In its April 2024 Arms Control Treaty Compliance Report, the US Department of State assessed that Russia had conducted “supercritical” nuclear tests (that is, tests with sufficient critical mass to create an explosion) without meeting its TTBT notification obligations. The State Department has also noted a lack of transparency about Russian test facility activities. Although the CTBT’s global verification regime is able to detect explosions below one kiloton, some experts judge that there is a verification gap for tests with small yields conducted deep underground. The prospect of covert testing has caused rising concerns about China’s activities, especially given the rapid expansion of its nuclear arsenal with new weapons types that require technical assurance, and the high level of activity observed at its test facilities.

Trump’s second motivation appears to be programmatic. Former Los Alamos National Laboratory Director Siegfried Hecker has noted that the plutonium cores (or “pits”) of thermonuclear weapons degrade over time and, since very few new pits have been produced by the United States since 1989, testing would “allow the US to answer some pressing questions about the fitness of its stockpile”. Since 1992, Washington has relied on a science-based approach (using modelling and analysis) to provide assurance rather than explosive tests. However, President Biden’s 2022 US Nuclear Posture Review stated, “As nuclear warhead system lifetimes are extended … assessments and certifications of warhead systems are increasingly challenged by limited surveillance hardware and testing opportunities.… Therefore, the United States maintains a nuclear explosive test readiness program in the event it is required to resolve technical uncertainties.” Having spelled out these conditions, the 2022 review was careful to confirm that the United States “does not envision or desire a return to nuclear explosive testing. Any resumption of nuclear testing would occur only at the President's explicit direction.”

Risky Business

Beyond these apparent motives, there could also be a deeper policy agenda in play. It is plausible that Trump is using “escalate to de-escalate” tactics to cajole Moscow and Beijing into dialing back their testing activities. It is also possible that the president is acting on grander ambitions to use a threatened resumption of larger-scale testing as leverage to achieve a breakthrough on trilateral regulation of nuclear arsenals, or to demonstrate the potency of US capabilities to bolster US great-power engagement.

Even if such aims have merit, this remains a highly risky maneuver. The geostrategic repercussions of re-opening the door to nuclear explosive testing would be serious.

Russia and China would likely want to demonstrate their own resolve (and capabilities) in response to any elevated level of US testing, and may also see technical benefits in less-fettered verification of the efficacy of their new systems. India and Pakistan probably have even greater technical incentive to test beyond existing constraints, given the early stage of their nuclear weapons development prior to the testing moratorium. They will also feel exposed to shifts in global and regional nuclear dynamics. Neither will North Korea want to be left out.

Trump’s emphasis that an expanded scope for US nuclear testing would be on “an equal basis” with other countries suggests he is alert to the need for restraint to avoid escalatory provocation. But he is betting that all actors have similar concepts of parity and will interpret US actions and intentions accurately. Tit-for-tat testing could easily become contagious and escalatory even if it starts out with modest boundary-pushing. Non-proliferation advocate Jeffrey Lewis has also warned of the dangerous dilemma inherent in opening the possibility of testing on a larger scale: “Even if all three start by only planning to go second, one of them might talk themselves into the importance of going first [and] one of them might decide that since everybody else is doing it, it’s better to get the jump and really get going.”

Any developments of this nature would elevate tensions across multiple points of international friction (in Europe, East Asia, South Asia, US-Russia/China), probably simultaneously. Testing resumption would more likely be a setback than a stimulus to already weak prospects for US-Russia-China arms control dialogue and would undermine efforts to formalize the testing moratorium through the CTBT. It could also prompt further troubling discussion about the merits of sovereign nuclear deterrents in Europe, Japan, and South Korea.

Action and Reaction

Moscow and Beijing have, to date, reacted predictably. Russian President Vladimir Putin ordered officials to draft proposals for a possible nuclear test—but without a specific deadline. Chief of the General Staff Valerii Gerasimov described these measures as a set of preparatory activities to ensure that Moscow had the capability to deliver a “timely response to the actions of the United States”, and thus in line with a prevailing “no-first-test” policy. In its response, Beijing sought to burnish its claims to be a reliable advocate for global stability by expressing the hope that the United States would maintain its nuclear testing, disarmament, and non-proliferation commitments.

These largely restrained initial reactions offer little reassurance. Any move towards resumption of full-scale testing would be perilous and could easily provoke an accelerated arms race or other international destabilization. As Hecker has concluded, “The bottom line is that even though the United States could derive important benefits from resumed nuclear testing, it would lose more than it stands to gain.”

The United States should therefore moderate any grand new ambitions in this arena and proceed cautiously. It should reaffirm its commitment to existing nuclear testing parameters and to science-based stockpile assurance frameworks that preserve the supercritical/explosive test moratorium. Russia and China undoubtedly need to move promptly to improve transparency and confidence around their own activities, but upping the nuclear ante to achieve this offers more risk than potential reward.

The views expressed herein are those solely of the author. GMF as an institution does not take positions.