The last year was characterized by fraught relations among the world’s great powers, who were engaged in vigorous nuclear modernization programs as the nuclear arms control regime continued to collapse. Within this general context, the contours of a peaceful and sustainable ending of Russia’s war against Ukraine are difficult to discern, and concerns remain about Russia’s possible use of nuclear weapons in this conflict.

In February 2023, Russian President Vladimir Putin announced his decision to “suspend” the New Strategic Arms Reduction Treaty (New START)—even though the treaty does not have such a suspension mechanism. While there are no indications that Russia has exceeded the treaty’s central limits, the lack of data exchanges, inspections, and other verification and transparency measures will over time decrease confidence in the status of Russia’s nuclear forces.

President Putin announced in March 2023 the deployment of tactical nuclear weapons in Belarus, but it remains unclear if any weapons have been moved. Russia retains some 2,000 tactical nuclear weapons for use in regional conflicts.

In October 2023, Russia’s Duma voted to withdraw Moscow's ratification of the Comprehensive Nuclear Test Ban Treaty. Like the United States, Russia remains a signatory to the treaty. While Putin has said that Russia won’t resume nuclear testing unless the United States does so, there have been reports about increased activity at nuclear test sites in Russia and China.

These developments are happening at a time when many nuclear weapon states are engaged in extensive modernization and expansion programs.

The United States and China are on the verge of a major nuclear arms race. One significant development in the United States is debate about whether the US nuclear arsenal may have to increase over the next decade to counter China’s expansion. The argument for an expanding US nuclear arsenal was articulated recently in a consensus report by the bipartisan Congressional Commission on the Strategic Posture of the United States, which argued that the United States and its allies must be ready to “deter and defeat” both Russia and China—simultaneously. The report recommended “fully and urgently executing the US nuclear modernization.” Recent history suggests that there will be tremendous pressure to further expand the US nuclear arsenal to compensate for the perceived deterrence gap with China, even if there is evidence that more nuclear weapons would actually diminish stability, and hence long-term US security.

Other nuclear crises continue to fester.

US government officials have acknowledged that the United States does not currently prioritize talks on a return to some form of the Iran nuclear deal (or Joint Comprehensive Plan of Action) “given all the other domestic strife inside Iran and the support that Iran has given to Russia in Ukraine.” Because the nuclear agreement remains in limbo, international monitors are increasingly unable to capture data on Iran’s nuclear efforts. This is a particularly worrisome development, given the escalating war in Israel/Gaza, which raises the possibility of a wider conflict in the Middle East. Iran now has the means to rapidly produce the fissile material for a small number of weapons within weeks of a decision to do so.

North Korea’s nuclear weapons program continues to advance steadily. In March 2023, North Korea released a number of photographs showing a row of warheads (“Hwasan-31”) of a new and smaller type, which could be deployable on shorter-range missiles. In April 2023, North Korea claimed it had successfully tested a solid-fuel intercontinental ballistic missile for the first time (“Hwasong-8”). These missiles can be moved and launched more rapidly, increasing the survivability of these forces. In response, South Korea has asked for a greater role in America’s nuclear commitments to defend the south, something that may ultimately fail to dull South Korea’s appetite for a deterrent of its own.

While May 2023 marked the 25th anniversary of India’s and Pakistan’s series of nuclear tests, both countries continue to accumulate weapons and delivery systems. There have been no constructive developments with regard to the nuclear forces, postures, and fissile material production of these two countries. Prospects for cooperation and threat reduction in the region remain bleak.

This will be the last Doomsday Clock statement before the 2024 US presidential election. All US presidential elections raise the issue of the immense and almost completely unfettered nuclear power vested in US presidents, each of whom has the sole authority to order the use of nuclear weapons. In the closing days of the previous administration, Chairman of the Joint Chiefs of Staff Gen. Mark A. Milley was sufficiently concerned with the then-president's temperament and comportment that he took steps to ensure that he would be consulted in the event that the president sought to launch nuclear weapons. The candidates’ suitability to shoulder the immense presidential authority to launch nuclear weapons has serious implications for international stability and should be a central concern in the 2024 presidential campaign.

Read the 2024 Doomsday Clock statement »