Never a More Important Time to Halt a Nuclear Arms Race
Following the February 2026 expiration of the New Strategic Arms Reduction Treaty (New START) between the United States and the Russian Federation and renewed debate in both Washington and Moscow about a possible return to nuclear explosive testing, the Comprehensive Nuclear Test Ban Treaty (CTBT) has shifted from the sidelines to the center of international nuclear restraint. With the numerical ceilings on the number of nuclear weapons eroding, one meaningful and continuing constraint remains: the global moratorium on nuclear explosive testing.
Arms control agreements like New START that cap arsenals through verification mechanisms are quantitative instruments. Nuclear explosive testing is qualitative; the tests verify a weapon’s performance, reliability, safety, and design yield. A resumption of testing also accelerates technological competition as well as horizontal and vertical proliferation.
The CTBT serves as a brake on that dynamic. By prohibiting all explosive tests, it reinforces a powerful norm against renewed nuclear experimentation. Even in the absence of the treaty’s entry into force, the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) notes that more than eight years have passed since the last declared or detected nuclear test explosion, an achievement defined by what has not occurred. Since the mid-1990s, nuclear testing has largely been supplanted by a norm against it.
The CTBTO: Walking the Walk
That restraint is not purely normative. The Preparatory Commission on the Comprehensive Nuclear Test Ban Treaty Organization demonstrates that science and international cooperation can strengthen transparency through its global verification architecture. For over three decades, the CTBTO’s global IMS has collected seismic, infrasound, radionuclide, and hydroacoustic data capable of detecting an underground nuclear explosion. More than 300 monitoring stations now operate worldwide. The integration of multiple sensing modalities strengthens confidence in the verification regime. With accumulated data, analysts affiliated with the CTBTO’s International Data Centre (IDC) can increasingly distinguish nuclear test signatures from mining blasts, conventional explosions, earthquakes, and other geologic phenomena. Today’s advances in machine learning promise to further refine CTBT’s detection and discrimination capabilities.
The IMS and the IDC provide objective insight into activities at known test locations, including North Korea’s Punggye-ri, China’s Lop Nur, Russia’s Novaya Zemlya, and the Nevada National Security Site. Over time, improvements in seismic analysis, radionuclide attribution, and remote sensing of ground deformation and tunneling activity will further reduce ambiguity and dampen nuclear tensions. Should the treaty enter into force, short-notice, on-site inspections would provide a powerful ground level mechanism to investigate suspected violations.
Renewed testing by the United States would almost certainly trigger reciprocal moves by Russia, China, North Korea, India, Pakistan, or others. The United States has recently alleged that China conducted an undeclared nuclear test in June 2020 in the vicinity of its Lop Nur test site. Competitive pressure to validate warhead designs or demonstrate nuclear resolve could rapidly intensify if a major power resumed testing. Once crossed, that threshold would be difficult to restore.
Benefits of Staying the Course
The CTBT is not without limitations: The treaty does not prohibit sub-critical experiments, and extremely low-yield or well-masked (i.e. decoupled) tests may currently evade detection. But these are technical gaps that can be reduced through continued expansion of the monitoring network, improvements in signal processing, and enhanced analytic techniques. The CTBTO also offers a forum for consultation and clarification to address ambiguous events and improve verification practices. Confidence-building measures, including applied training and realistic exercises, strengthen analysts’ ability to process, interpret, and report data on suspected nuclear tests. By strengthening transparency through established, accepted technical means, the work of the organization should be recognized and positioned to build on the accomplishments of New START.
Political, legal, and technical challenges persist, most notably the CTBT’s unfulfilled entry into force. However, now is not the time to return to an uncertain future punctuated by nuclear tests. Further testing benefits those states with smaller nuclear weapons stockpiles and limited testing data, in particular, China and North Korea. Large investments by the United States in science-based stockpile stewardship already ensure the readiness of U.S. nuclear weapons.
Don’t Abandon the Test Ban
Now is not the time to give up on the CTBT. As an institution, the work of the CTBTO deserves international support, continued funding, and the benefit of the latest technical capabilities. Ensuring open access to IMS data and deepening the cooperation between the scientific and security communities are investments in strategic stability. The infrastructure is built. The norm is established. The capability is proven. What is needed is the political will to prevent a return to a past era of nuclear explosions and an escalating arms race.
Header image: OSI – Tabletop Exercise – Dec 2023. By The Official CTBTO Photostream
Hiding in Plain Sight: Why the Comprehensive Test Ban Treaty Matters After New START
By David Kenneth Smith
Nonproliferation
With the expiration of New START, the Comprehensive Nuclear Test Ban Treaty (CTBT) has become central to preventing renewed nuclear testing and curbing unconstrained arms competition. By reinforcing a global norm against all nuclear tests, including low-yield experiments, the CTBT serves as a critical check on testing methodologies and weapons development. Prioritizing international support, funding, and access to the Comprehensive Nuclear Test Ban Treaty Organization’s International Monitoring System data ensures that the body will continue to uphold nuclear restraint after New START and prevent a return to an era of testing-driven arms escalation.
Never a More Important Time to Halt a Nuclear Arms Race
Following the February 2026 expiration of the New Strategic Arms Reduction Treaty (New START) between the United States and the Russian Federation and renewed debate in both Washington and Moscow about a possible return to nuclear explosive testing, the Comprehensive Nuclear Test Ban Treaty (CTBT) has shifted from the sidelines to the center of international nuclear restraint. With the numerical ceilings on the number of nuclear weapons eroding, one meaningful and continuing constraint remains: the global moratorium on nuclear explosive testing.
Arms control agreements like New START that cap arsenals through verification mechanisms are quantitative instruments. Nuclear explosive testing is qualitative; the tests verify a weapon’s performance, reliability, safety, and design yield. A resumption of testing also accelerates technological competition as well as horizontal and vertical proliferation.
The CTBT serves as a brake on that dynamic. By prohibiting all explosive tests, it reinforces a powerful norm against renewed nuclear experimentation. Even in the absence of the treaty’s entry into force, the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) notes that more than eight years have passed since the last declared or detected nuclear test explosion, an achievement defined by what has not occurred. Since the mid-1990s, nuclear testing has largely been supplanted by a norm against it.
The CTBTO: Walking the Walk
That restraint is not purely normative. The Preparatory Commission on the Comprehensive Nuclear Test Ban Treaty Organization demonstrates that science and international cooperation can strengthen transparency through its global verification architecture. For over three decades, the CTBTO’s global IMS has collected seismic, infrasound, radionuclide, and hydroacoustic data capable of detecting an underground nuclear explosion. More than 300 monitoring stations now operate worldwide. The integration of multiple sensing modalities strengthens confidence in the verification regime. With accumulated data, analysts affiliated with the CTBTO’s International Data Centre (IDC) can increasingly distinguish nuclear test signatures from mining blasts, conventional explosions, earthquakes, and other geologic phenomena. Today’s advances in machine learning promise to further refine CTBT’s detection and discrimination capabilities.
The IMS and the IDC provide objective insight into activities at known test locations, including North Korea’s Punggye-ri, China’s Lop Nur, Russia’s Novaya Zemlya, and the Nevada National Security Site. Over time, improvements in seismic analysis, radionuclide attribution, and remote sensing of ground deformation and tunneling activity will further reduce ambiguity and dampen nuclear tensions. Should the treaty enter into force, short-notice, on-site inspections would provide a powerful ground level mechanism to investigate suspected violations.
Renewed testing by the United States would almost certainly trigger reciprocal moves by Russia, China, North Korea, India, Pakistan, or others. The United States has recently alleged that China conducted an undeclared nuclear test in June 2020 in the vicinity of its Lop Nur test site. Competitive pressure to validate warhead designs or demonstrate nuclear resolve could rapidly intensify if a major power resumed testing. Once crossed, that threshold would be difficult to restore.
Benefits of Staying the Course
The CTBT is not without limitations: The treaty does not prohibit sub-critical experiments, and extremely low-yield or well-masked (i.e. decoupled) tests may currently evade detection. But these are technical gaps that can be reduced through continued expansion of the monitoring network, improvements in signal processing, and enhanced analytic techniques. The CTBTO also offers a forum for consultation and clarification to address ambiguous events and improve verification practices. Confidence-building measures, including applied training and realistic exercises, strengthen analysts’ ability to process, interpret, and report data on suspected nuclear tests. By strengthening transparency through established, accepted technical means, the work of the organization should be recognized and positioned to build on the accomplishments of New START.
Political, legal, and technical challenges persist, most notably the CTBT’s unfulfilled entry into force. However, now is not the time to return to an uncertain future punctuated by nuclear tests. Further testing benefits those states with smaller nuclear weapons stockpiles and limited testing data, in particular, China and North Korea. Large investments by the United States in science-based stockpile stewardship already ensure the readiness of U.S. nuclear weapons.
Don’t Abandon the Test Ban
Now is not the time to give up on the CTBT. As an institution, the work of the CTBTO deserves international support, continued funding, and the benefit of the latest technical capabilities. Ensuring open access to IMS data and deepening the cooperation between the scientific and security communities are investments in strategic stability. The infrastructure is built. The norm is established. The capability is proven. What is needed is the political will to prevent a return to a past era of nuclear explosions and an escalating arms race.
Header image: OSI – Tabletop Exercise – Dec 2023. By The Official CTBTO Photostream
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