After Trump takes office on 20 January, his administration will face greater nuclear challenges and threats to the United States and its allies than during his first term (2017-2021). Although President Joe Biden initially sought to reduce the role of nuclear weapons in U.S. security policy, in recent months the Pentagon has been working on options to increase the nuclear arsenal. Biden administration officials warn that it may be necessary in the future to deter several states both hostile to the U.S. and increasing their nuclear forces, namely Russia, China and North Korea (DPRK).

Russia has been escalating its nuclear threats, particularly to discourage NATO states from supporting Ukraine since the Russian full-scale invasion in 2022, and is expanding its nuclear forces not covered by the New START treaty. For the most part, these are so-called non-strategic forces, which, according to U.S. intelligence, number up to 2,000 warheads. They include both intermediate-range (such as the Oreshnik missile used against Ukraine in a non-nuclear version on 21 November) and shorter-range systems (such as Iskander ballistic missiles). In addition, Russia has suspended the exchange of information and mutual inspections under the New START treaty, impeding its verification. Under this agreement, the two countries can each deploy up to 1,550 warheads ready for use by strategic (intercontinental) ballistic missiles and bombers. Russia places the ending of U.S. military aid to Ukraine as the most important condition for a return to full implementation of New START and talks on the next agreement.

However, the main catalyst for the growing U.S. discussion on a potential increase in nuclear forces is the rapid expansion of the Chinese nuclear arsenal. According to the U.S., it has grown from just over 200 operational warheads in 2020 to 500 today and will reach over 1,000 by 2030, mostly for intercontinental missiles. In July, China suspended the short-lived arms-control talks with the U.S., demanding an end to American arms sales to Taiwan. North Korea’s nuclear arsenal—unofficially estimated at less than 100 warheads—is growing as well, with a variety of systems with different ranges being brought into service.

Towards a Larger U.S. Nuclear Force

 In response to the deteriorating security environment, the U.S. is likely to increase its nuclear forces. In October 2023, the congressionally-mandated bipartisan U.S. Strategic Posture Commission (SPC) assessed that the risk of simultaneous conflicts with China and Russia will increase between 2027 and 2035, and that it is “necessary but not sufficient” to fully implement the delayed modernisation of U.S. nuclear forces (initiated during the Barack Obama presidency). Of note, Republican politicians and experts mostly take a tougher stance than Democratic circles, including by calling for the U.S. nuclear forces to already be expanded. Trump advocated this at the beginning of his first term.

The U.S. could increase the number of deployed nuclear warheads relatively quickly and even double it by deploying reserve warheads on intercontinental missiles, as well as by reversing modifications that stripped some bombers and submarine launchers of the capability to use nuclear weapons. If Trump decided to take such action before New START expires in January 2026, he would have to terminate it. Such a scenario is possible, especially since during his first term Trump criticised the agreement and only allowed for a short extension in case of Russian concessions, while Biden extended it unconditionally for five years. Trump may also not only accelerate the production of new strategic systems—currently slated to replace existing ones— but also increase it. Such an expansion, however, would be much more time-consuming.

Changes are also possible in the U.S. non-strategic nuclear forces, currently consisting solely of bombs carried by multirole aircraft provided by the U.S. and several NATO allies (according to the Federation of American Scientists, this arsenal includes around 200 warheads, of which around 100 are in Europe). In 2023, the SPC identified modifications to non-strategic capabilities as urgently needed, primarily to strengthen the ability to respond proportionately—and thus less escalatory and more credibly—to potential limited nuclear attacks by U.S. adversaries in Asia and Europe. The solution most often put forward by U.S. experts is to accelerate the development of a nuclear sea-launched cruise missile (SLCM-N) so that it would have been already ready before 2030 (e.g., by adapting the conventional Tomahawk). The SLCM-N programme was started by the first Trump administration, while Biden wanted to cancel it as unnecessary. However, Congress mandated the missile to be deployed by 2034. Some conservative experts and politicians also propose acquiring additional systems, such as air- or ground-launched cruise missiles.

Uncertain Policy Towards Allies

 While an increase in U.S. nuclear forces, especially non-strategic ones, may strengthen the security of U.S. allies, Trump’s exact approach to cooperation in NATO and the impact of his other actions on the credibility of the Alliance’s nuclear deterrence are difficult to predict.

Trump and his advisors are vowing greater pressure on allies to increase defence spending than in his first term. While the goal is a legitimate one, too much pressure—such as Trump questioning his willingness to defend allies—could weaken the credibility of U.S. deterrence. Moreover, it is unclear whether in Trump’s view an increase in the forward presence of U.S. nuclear forces would be compatible with efforts to extract greater allied defence expenditures. It is also possible that he would consider additional nuclear deployments in Europe as provocative, given that he and some of his associates have been expressing concerns about U.S. military aid to Ukraine being escalatory and potentially leading to “World War III”. Moreover, if Trump’s attempt to end the conflict is negative for Ukraine, it could encourage Russia (and other states) to launch further aggressions backed by nuclear threats.

An additional complication for NATO states will be the increasing calls among Republican experts for a reduction in U.S. military involvement in Europe in order to devote greater resources to the competition with China (this view, however, was not shared by the SPC, among others). Such concepts usually assume the withdrawal of most or even all U.S. conventional forces from Europe, but the maintenance of the U.S. nuclear deterrence in NATO. Some of these proposals even call for strengthening it. There are, for example, postulates to deploy additional U.S. nuclear delivery systems in Europe or to expand nuclear-sharing: to certify F-35 aircraft from flank states (including Poland and Finland) to carry U.S. nuclear bombs, or potentially even to deploy nuclear warheads there. However, even with such moves, drastic reductions in U.S. conventional troops, especially in countries most vulnerable to Russian attack, would raise doubts about whether the U.S. would be willing to risk a nuclear war to defend allies.

Conclusions and Recommendations

 U.S. political and military engagement remains crucial to the credibility of NATO’s nuclear deterrent, but European allies should also increase their contribution. This would help counter the threat from Russia, especially as the eventuality of conflict in Asia will increasingly absorb U.S. nuclear forces and their supporting assets (e.g., tanker aircraft). Strengthening allied involvement is even more important in the face of the uncertainty about future U.S. policy in NATO. In this case, it could facilitate both developing cooperation with the new administration and limiting the negative effects of its potential moves.

With Trump’s expected interest in increasing both nuclear forces and allies’ responsibility for their own security, it is possible that the U.S. will be open to broadening the participation of NATO countries in nuclear-sharing. Poland should explore such a possibility in bilateral talks and within NATO. Although the nuclear forces of the Alliance’s other two nuclear powers are much smaller than those of the U.S., it is also in Poland’s interest to develop a dialogue with France about increasing the role of its nuclear arsenal in protecting Europe, as well as to engage in similar talks with the UK.

Further enhancement of non-nuclear forces may also help to deter Russia from using nuclear weapons, in addition to strengthening defences against conventional aggression. For example, stronger missile defences may reduce Russia’s chances of successfully conducting limited nuclear strikes. In turn, conventional precision-guided missiles and other strike capabilities can facilitate allied nuclear operations by weakening enemy air defences. While they cannot provide as strong a deterrent as the much more destructive nuclear forces, it is possible that in some cases they would also provide a sufficient means of retaliation for a limited nuclear attack. This is an additional reason for Poland and European allies to acquire ground-launched medium-range conventional missiles.