The Treaty Is Dead. Relax.

Arms control ends, constraints remain

Picture: U.S. Space Force

On Thursday, 5 February, New START, the last major arms control treaty between the United States and Russia, expired without a successor.

For the first time in more than 50 years, the world’s two largest nuclear powers will face no formal limits on their nuclear arsenals. At the same time, the last formal transparency mechanism in nuclear statecraft will disappear. Neither the United States nor Russia will be obligated to report the number or status of their strategic nuclear warheads.

Nevertheless, it is highly unlikely that a new major nuclear arms race is looming, at least for now.

A new nuclear arms race?

The New START Treaty capped Russian and U.S. nuclear arsenals at 800 strategic nuclear delivery vehicles, including ground- and submarine-launched ICBMs and strategic bombers, as well as 1,550 strategic nuclear warheads deployed on these delivery vehicles. The treaty did not limit non-strategic (sometimes called “tactical”) nuclear assets, either delivery vehicles or warheads, nor did it cap nuclear warhead reserve arsenals, meaning stored, non-deployed strategic nuclear warheads. With the treaty expiring, both Russia and the United States could, in theory, exceed the former New START deployment limits.

In practice, however, major nuclear arms buildups are unlikely, especially in Russia. Russia remains engaged in a major land war in Ukraine that absorbs enormous amounts of resources. Economic reporting suggests that Russia’s defense industry is already heavily overstretched. Together, these factors mean that any large-scale expansion of Russia’s strategic nuclear arsenal would be difficult to realize quickly and would come at a high cost, likely at the expense of conventional capabilities needed to sustain the war effort in Ukraine.

That said, a moderate increase in strategic nuclear warheads is possible, notably by increasing the number of “uploaded” warheads on existing ICBMs. Russian ICBMs already in service can be fitted with additional warheads up to their design capacity without building new missiles. Across the deployed ICBM force, Russia could plausibly add on the order of 300 to 600 warheads, depending on how aggressively it chose to upload.

Whether Russia will do so is far from certain and may depend on U.S. actions after the treaty ends. If the United States decides to increase the number of deployed nuclear warheads, a Russian response aimed at restoring parity would appear likely. That said, Russia could also move independently to raise the number of deployed strategic nuclear warheads, for example, to place pressure on Europe by increasing the perceived level of nuclear risk.

From a U.S. perspective, modest mutual increases in nuclear warhead numbers would have mixed implications. On the one hand, stable numbers of nuclear delivery vehicles combined with moderate increases in warhead counts could make the prospects of a successful preemptive counterforce strike for damage-limitation purposes more feasible, as the number of warheads available per aimpoint (corresponding to delivery vehicle deployment sites) increases. On the other hand, larger warhead arsenals would also raise the stakes of a failed counterforce strike, since surviving delivery vehicles could carry more warheads, allowing them to inflict greater damage in response.

From a European perspective, a moderately larger Russian strategic nuclear arsenal would not change a lot. Russia already deploys enough warheads to threaten catastrophic damage against major European population centers and retains the world’s largest, several-thousand-warhead-strong, non-strategic nuclear arsenal, which was not covered by New START and therefore never subject to limits.

A new start after New START?

Some media reports suggest talks about a follow-on arms control instrument between the United States and Russia. A comprehensive follow-on treaty, however, appears unlikely to emerge any time soon for three main reasons.

First, Russia’s blatant violation of the INF Treaty, which governed the deployment of intermediate-range nuclear forces and for which Russia never accepted responsibility, makes it difficult to justify new agreements. Even setting aside Russia’s disregard for international law in Ukraine for a moment, its record of arms control treaty violations raises the question of how the United States could be confident that Russia would not violate future commitments as well.

Second, from a U.S. perspective, China’s rapid nuclear expansion renders a bilateral U.S.-Russia arms control agreement increasingly untenable. China is estimated to have expanded its arsenal to around 600 warheads, roughly double its size five years ago, and may reach about 1,000 by 2030. The U.S. nuclear force is expected to deter two nuclear great powers simultaneously, China and Russia. While this was manageable when Chinese warhead numbers were low, it becomes increasingly challenging as China’s arsenal grows in size and capability. As a result, any New START follow-on treaty would likely need to include China – as demanded by U.S. policymakers –, but China is highly unlikely to accept limits on its nuclear forces until it reaches rough parity with those of Russia and the United States, a point that is still quite a distance away.

Third, even if political barriers could be overcome and negotiations began soon, their completion would likely take months, if not years, particularly if they included a verification regime comparable to that of New START and involved more than two actors. Negotiating such regimes requires agreement on detailed protocols for telemetry sharing, verification visits, and warhead and delivery vehicle accounting, among other issues. Matters would become even more complicated and contentious if Russia, and potentially China, demanded the inclusion of U.S. strategic missile defense assets, which they have implied would be a core demand.

Overall, this suggests that, for the foreseeable future, the world is likely to remain without a major arms control agreement between the two largest nuclear powers. Because neither Russia nor the United States will be obligated to report on deployed strategic nuclear warhead numbers, transparency will decline.

The United States and Europe will retain some visibility into Russia’s nuclear arsenal through so-called “national technical means of verification”, including satellite imagery as well as signals and electronic intelligence, among others. As a result, aggressive expansions of Russia’s deployed nuclear arsenal would likely not go unnoticed even in the absence of Russian reporting. For example, major movements of strategic nuclear warheads, the deployment of new ICBM launchers, and the refurbishment of decommissioned ICBM silos would be extremely difficult to conceal.

Conventional priorities

Even in the absence of a formal arms control treaty, a nuclear arms race on the scale of the Cold War, in which the Soviet Union and the United States added thousands of delivery vehicles and tens of thousands of nuclear warheads, is difficult to imagine. Russia, in particular, and the United States lack the industrial and financial capacity to pursue such an effort, especially amid competing defense-industrial priorities in the conventional domain.

From a European perspective, strengthening conventional defense and deterring Russian adventurism beyond Ukraine remain the top priorities. This does not change, even if a modest increase in deployed Russian nuclear warheads were to materialize.