The current debate around a possible resumption of nuclear testing introduces a new level of brinkmanship in today’s increasingly fraught geopolitical climate. There is a high risk that the testing moratorium is being weaponised for the sake of great-power competition. European states, including nuclear weapon states, must speak out against nuclear testing, making it clear that it is unwise, unnecessary and unwelcome.

A fertile ground for Trump’s testing comments

Regardless of how unprovoked and irrational the President’s comments on Truth Social seemed, unfortunately, there is fertile ground for them. Since 2019, radical voices have been calling for the resumption of US nuclear testing to strengthen deterrence.

Former National Security Advisor Robert O’Brien, as well as the Heritage Foundation and Project 2025, continue to advocate for the United States to abandon the decades-long testing moratorium established by the Comprehensive Nuclear-Test-Ban Treaty (CTBT), despite the harmful implications for both the international community and their own country.

However, there is no need to look to Trump-aligned think tanks for confirmation of this today. Even the Atlantic Council hailed Trump’s confusing comments as a “welcome sign that he is no longer easily swayed by Putin’s dramatics and recognises the dangers of allowing himself to be intimidated”.

Earlier, in 2020, the Washington Post reported on discussions among officials regarding the resumption of nuclear testing. According to the article, this was intended to create leverage for future arms control negotiations with Russia and China.

Recent US concerns over Russia’s and China’s adherence to “zero-yield” standards

While it is widely acknowledged, including by US officials, that the DPRK is the only country to have conducted nuclear explosive tests this century, the US has previously expressed concerns about other countries adhering to the ‘zero-yield’ standard for nuclear testing.

These allegations arose during the first term of the Trump administration and were repeated by the Biden administration. The 2019 State Department Compliance Report expressed concern that “the United States, including the Intelligence Community, has assessed that Russia has conducted nuclear weapons tests that have created nuclear yield”. The 2022 Compliance Report accused Russia of conducting supercritical nuclear weapons tests and noted uncertainty surrounding activities at the Novaya Zemlya test site. However, the report did not identify any new compliance developments. The same applies to the 2023–25 period.

Concerning China, the 2020 Report expressed concerns about activities at the Lop Nur nuclear weapons testing site, questioning Beijing’s commitment to the US zero-yield standard. These concerns were reiterated in the 2022 Report, but no new issues regarding adherence have been identified in more recent reports.

The military significance of hydro-nuclear test experiments

For decades, US policymakers have been divided over the question of whether other countries adhere to the US zero-yield standard (i.e. only conducting hydrodynamic testing) and whether hydronuclear tests that create a very low nuclear yield could be conducted without detection.

A 2012 report by the National Research Council noted that with regard to the Russian Novaya Zemlya test site that “perhaps an average of six ‘non-explosive’ nuclear weapon-related experiments are conducted there annually… It is conceivable that at least some of these experiments might have resulted in very low nuclear yields (< 1 ton), which could be completely contained in an explosive test vessel underground”.

However, a different question is whether these tests have military value, or whether they are useful only for maintaining the safety of weapons? The 2012 report concludes that they would not help Russia advance its strategic capabilities.

A comprehensive report by Lawrence Livermore National Laboratory about the CTBT, published in 2020, argues in a similar sense that “[in] the debates surrounding the moratorium on nuclear testing, it is asserted that hydro-nuclear testing is relatively unimportant, especially for advanced nuclear states with significant historical testing experience such as the United States or Russia”. However, the report continues that, other than the US, whose nuclear weapons maintenance relies on the advanced Stockpile Stewardship Programme, Russia’s arsenal could benefit from hydronuclear experiments to extend the life cycle of its weapons.

The authors conclude that it is unclear to what extent China, which lacks Cold War hydronuclear test experience, would benefit from such tests regarding its arsenal modernisation.   

How does the US benefit from the testing moratorium?

In general, there seems to be little concern that hydronuclear experiments could become anything other than an additional means of ensuring the safety of weapons and that they would not help countries to develop new capabilities. Therefore, there are clear benefits for the US in protecting the testing moratorium, even if Russia and China have conducted hydronuclear tests. 

Perhaps the most obvious reason for the US to uphold the CTBT is that it prevents China from conducting tests. Other than the US (over 1,000 tests) and Soviet Union/Russia (over 700), China has tested less than 50 times. It thus lags behind France and is on par with the number of British nuclear weapons tests. The Chinese data set therefore is much smaller than the vast amounts of data that Washington and Moscow gathered—which is why Beijing would have more to gain from a resumption of explosive testing.

So far, China has not expressed a desire to resume testing. However, it would be surprising if Beijing were not assessing whether and how Chinese interests would be affected if the global testing norm were to erode.

Furthermore, the CTBT is an established component of the global non-proliferation framework. North Korea’s actions have demonstrated that there are serious economic and reputational consequences for countries that reject internationally accepted normative frameworks such as the NPT and the CTBT. However, if such norms were to erode — and it is conceivable that a collapse of the CTBT might precede an erosion of the NPT — then debates about nuclear weapons in states such as South Korea and Japan might be reinvigorated. The US has nothing to gain from an increasing number of nuclear weapons possessors worldwide.

It should also be noted that, technically speaking, the US would not benefit from resuming nuclear explosive testing. The Stockpile Stewardship Programme is robust, and the US has already collected enough data through extensive testing. Therefore, the primary reason for testing would be an erroneous interpretation of deterrence, or rather, brinkmanship. However, it is difficult to see how such an irresponsible move would strengthen deterrence, rather than massively increase strategic instability and worsen existing tensions, thereby damaging any long-term prospects for risk reduction and arms control.

It is also likely that President Trump’s comments regarding Pakistan’s alleged testing will intensify tensions between Islamabad and New Delhi, even if these allegations are false. None of the recent State Department Compliance Reports have raised any concerns regarding Pakistan. But such public allegations can already have a detrimental effect for relations between the two countries.

What European states can do

In light of the irrationality of the US administration, there is little that Europeans can do. However, it would be dangerous and irresponsible for them to remain silent in the current situation. While some states may be more concerned than others, it is important for Europe to speak with one voice on this issue and make it clear that nuclear testing is unwise, unnecessary and unwelcome.

As the two P5 states that would certainly have no interest in resuming testing, nor in allowing others to do so, France and the UK have a particular responsibility to speak up in the P5 format, at the upcoming NPT Review Conference, and through bilateral channels.

They need to remind the US, but also China and Russia, that nuclear testing comes with immense costs. As Gregory Kulacki wrote in a noteworthy article for the Union of Concerned Scientists, the costs would outweigh “imagined benefits”.

They can also emphasise that resuming nuclear testing could prompt other nuclear “newcomers” to follow suit, inevitably increasing geopolitical and regional tensions, as well as posing potential harm to human beings and ecosystems, given that the risks associated with nuclear testing cannot be adequately contained—after all, nuclear testing scars one’s own population.

European leaders should also demand that the US clarifies whether they have new evidence about the testing activities of Russia, China, North Korea and Pakistan. The most recent Compliance Report, published in April 2025, did not mention anything regarding North Korean and Pakistani testing activities.

This is an urgent issue on which the European nuclear weapons states, in particular, should take a clear stance. Trump has paved the way for a highly detrimental development, and Russia will certainly not hesitate to further escalate the situation. The international community must speak out about the dramatic consequences of a possible collapse of the testing moratorium, including the potential demise of the NPT — a conceivable outcome of such a policy shift.

The European Leadership Network itself as an institution holds no formal policy positions. The opinions articulated above represent the views of the authors rather than the European Leadership Network or its members. The ELN aims to encourage debates that will help develop Europe’s capacity to address the pressing foreign, defence, and security policy challenges of our time, to further its charitable purposes.

Image credit: Wikimedia Commons / The White House