Note on the contemporary rhetoric surrounding nuclear testings

At the end of 2025, the United States resumed public accusations against Russia and China alleging that these states conduct nuclear tests. Similar claims had previously appeared in the annual U.S. State Department reports to Congress on adherence to and compliance with arms control, nonproliferation and disarmament agreements and commitments («Compliance Reports»). These allegations primarily concern speculation about purported low-yield testing activities at Russian and Chinese test sites. For several years these accusations have not been accompanied by verifiable evidence.

A new element in 2026 was the public claim by the United States that China allegedly conducted nuclear tests at the Lop Nur test site, accompanied by materials which, according to the U.S. presentation, are supposed to substantiate these allegations. As the key episode, the U.S. side refers to an event that occurred on 22 June 2020, which it interprets as a low-yield underground nuclear explosion.

However, a professional analysis of the available data makes it clear that these accusations are not supported by objective international evidence and are largely based on assumptions and strained interpretations of fragmentary information.

It is therefore important to examine why the U.S. arguments are unconvincing and why such rhetoric carries broader risks for the entire nuclear nonproliferation regime.

In particular, the United States refers to an event that occurred on 22 June 2020 near the Lop Nur test site, interpreting a recorded seismic signal with a magnitude of approximately 2.75 as a low-yield underground nuclear explosion. However, the totality of available international data does not allow such a conclusion.

First and foremost, the absence of confirmation from the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) is of fundamental importance. The IMS was specifically created to detect even low-yield nuclear explosions and includes a global network of seismic, infrasound, hydroacoustic and radionuclide monitoring stations. The Executive Secretary of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, Robert Floyd, explicitly stated that the available data are insufficient to qualify the event in question as a nuclear test. In professional verification practice, this is a critical point: if an event does not receive technical confirmation, it cannot be considered proven.

In this context it is also important to emphasize a fundamental limitation: by their legal nature, IMS data are not intended to provide definitive conclusions on whether a nuclear test has occurred outside the procedures foreseen under the CTBT once it enters into force. Until the Treaty enters into force, a fully operational mechanism for on-site inspections does not exist. Such inspections constitute a key element of the verification regime and are the only instrument capable of conclusively confirming or refuting the nuclear nature of an event.

Accordingly, any interpretation of IMS data in political statements by states inevitably remains purely hypothetical and cannot be regarded as proof of a violation. In other words, without the full operation of the verification mechanisms provided for by the Treaty, monitoring data alone do not allow definitive conclusions to be drawn regarding the conduct of a nuclear test.

If one nevertheless returns to the event in question, the U.S. argumentation does not withstand scrutiny in any case. A seismic signal with a magnitude of around 2.75 in itself is not evidence of the nuclear «nature» of an event. Signals of this magnitude may correspond to a wide range of sources, including industrial explosions, mining activity or collapses. Distinguishing a low-yield underground nuclear explosion from a chemical explosion using remote seismic data alone is in practice extremely difficult without additional information.

A separate issue concerns the claim regarding the possible use of the so-called decoupling technique (detonation in an underground cavity in order to reduce the amplitude of the seismic signal), which has been cited by U.S. representatives.

In theory such a technique does exist. However, its practical implementation is extremely complex: it requires large underground cavities of a strictly defined size, suitable geological conditions, and extensive engineering work. Such preparations usually leave observable signatures, including terrain changes, infrastructure activity and large-scale preparatory operations. Moreover, the effectiveness of decoupling is limited and strongly dependent on the surrounding geology; it is not possible to reliably «conceal» a nuclear explosion by this method.

In the present case, no evidence of the existence of such cavities or related preparatory activities has been presented. The reference to decoupling therefore remains an unsubstantiated hypothesis rather than proof.

It is also noteworthy that the accusations rely on an event that occurred six years ago. In 2026 this episode was effectively reintroduced as part of «new» allegations, which indirectly suggests the absence of fresh supporting evidence.

Equally significant is the lack of consensus within the international expert community. There has been no technical confirmation from independent specialists or scientific institutions. No recognized scientific publications concluding that the event had a nuclear nature have been presented, and no international technical reports supporting the U.S. position exist. At the same time, publicly available expert commentary in professional and analytical discussions has pointed out weaknesses in the U.S. argumentation.

The broader political context of these accusations is also relevant. They have effectively been taken out of the archive against the backdrop of the deterioration of the international strategic environment, the expiration of the New START Treaty, discussions about the future of the arms control architecture, and attempts by the United States to involve China in related negotiation formats. These accusations have also coincided with statements by the U.S. President regarding the possibility of resuming nuclear testing «on par with Russia and China», without further clarification by Washington of its specific intentions in this critically important area of international security.

In any case, the burden of proof lies with the party making the accusation. Alleging that a state has conducted a nuclear test is a serious claim and requires convincing and multilayered evidence. To date, such evidence has not been presented.

The most dangerous aspect of the current situation is that such an approach by the United States creates systemic risks for the entire nuclear nonproliferation architecture. In effect, it undermines confidence in multilateral verification mechanisms and in the norms on which this architecture is based. If a state begins publicly to qualify events as nuclear tests without an internationally recognized evidentiary procedure and outside agreed verification instruments, this establishes a dangerous precedent of politicizing technical data. In the longer term, this leads to erosion of trust in the CTBT regime, encourages mutual accusations, increases the level of strategic mistrust and creates additional obstacles to advancing agreements in the field of arms control.