How would Trump and Biden handle US nuclear policy upon reelection?

Few issues are as potentially consequential as U.S. nuclear policy. What are Donald Trump and Joe Biden likely to do with respect to deterrence and arms control if reelected? Their previous terms in office suggest important differences—not only on specific nuclear policy issues but also in their overall approach to managing nuclear risk. These differences matter because of the enormous presidential latitude with respect to nuclear decision-making, including presidents’ sole authority to launch nuclear weapons without authorization from other parts of the government.

While in office, Trump was often confrontational in his dealings with other nuclear powers and was openly skeptical of the alliance relationships that depend on U.S. nuclear guarantees. He was actively hostile toward arms control. By contrast, Biden has been relatively cautious in the nuclear domain, prioritizing stability in relationships with other nuclear powers and strengthening American nuclear assurances to allies. While valuing a robust deterrent, Biden also has a long-standing commitment to arms control.

What Trump did on nuclear policy while in office

Trump’s decision to renege on the Iran nuclear deal—despite the State Department certifying that Iran was complying with its terms—was likely the most significant nuclear policy decision of his time in office. Since then, Iran has progressed steadily closer to a nuclear weapon, much closer than it would have had the deal remained in place.

Coming in a close second in terms of consequential nuclear decision-making was Trump’s policy toward North Korea. Much fanfare accompanied his summit with Kim Jong Un in Singapore in June 2018, but the meeting produced no substantive restraints on the North Korean arsenal. In fact, North Korea significantly expanded and improved its nuclear arsenal on Trump’s watch, gaining the ability to hit the continental United States with a nuclear-tipped ballistic missile.

Furthermore, Trump actively stoked a dangerous nuclear crisis with North Korea in the period leading up to the summit. He threatened that North Korea would be “met with fire, fury, and frankly power, the likes of which this world has never seen before,” which most observers took to be a thinly veiled nuclear threat. At another point, he tweeted of Kim, “Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!” Trump was later revealed to have privately considered using a nuclear weapon against North Korea while falsely blaming it on another country.

Finally, the Trump administration was highly skeptical of arms control with other nuclear powers. It withdrew the United States from the long-standing 1992 Open Skies Treaty, and it failed to reach an agreement with Russia to extend New START, the only treaty regulating strategic nuclear weapons in the world’s two largest nuclear arsenals. Trump also withdrew the United States from the 1987 Intermediate-Range Nuclear Forces (INF) treaty, though long-standing Russian violations of the treaty deserve more blame for that than the Trump administration. In addition, the Trump administration deployed a new low-yield submarine-launched ballistic missile and initiated a program to build a new nuclear sea-launched cruise missile.

What Trump might do on nuclear policy if reelected

The first Trump administration provides a good guide to what to expect on nuclear policy in a second Trump administration: active hostility toward arms control and a cavalier attitude toward nuclear risk. There is little reason to think that Trump’s views on nuclear issues have changed over the last four years in ways that would alter his policy course.

What has changed, unfortunately, is the propensity for Trump’s tendencies to produce more serious nuclear risks. Iran is now closer to a nuclear weapon. North Korea’s arsenal can more directly threaten the United States. China’s nuclear arsenal is expanding as it becomes increasingly confrontational toward Taiwan. And Russia is now engaged in a major conventional war on NATO’s border. Any of these situations could produce a nuclear crisis during a future Trump administration—one that Trump might be prone to escalate rather than tamp down, though he has also claimed his administration would somehow end the war within 24 hours of taking office.

Trump’s deep disdain for U.S. alliances is also likely to have important implications for nuclear proliferation if he is reelected. These alliances extend U.S. nuclear protection to countries such as Japan, South Korea, and NATO members partly to ensure that they forego building their own nuclear weapons. Were Trump to return to office and seek to reduce or eliminate these commitments, these countries would have good reason to fear the reliability of the U.S. nuclear umbrella. They might seek their own nuclear weapons or accommodation with nuclear-armed adversaries such as China and Russia as a result.

What Biden has done on nuclear policy while in office

Biden’s most important nuclear achievement has been successfully deterring Russian nuclear escalation over the war in Ukraine: Russia has not used nuclear weapons against NATO members or against Ukraine itself. Despite Russian saber-rattling and serious Western concern that Moscow might turn to its arsenal when facing conventional setbacks on the battlefield, Russia has repeatedly pulled back from the brink. This is in significant part because Biden has effectively communicated that the United States will defend NATO, and also that it would respond forcefully (though almost certainly not with nuclear weapons) to Russian nuclear use in Ukraine. While providing unprecedented conventional military aid to Ukraine, the Biden administration has nevertheless been careful to avoid provoking Russia. For example, it has (mostly) constrained Ukraine’s ability to conduct longer-range attacks on Russian territory with U.S.-supplied weapons.

Furthermore, the Biden administration has taken steps to stabilize the overall strategic nuclear relationship with Russia. For example, it postponed a nuclear missile test in March 2022 in order to avoid any Russian misperceptions of U.S. nuclear intentions. And it has continued to adhere to the central limits of the New START treaty, even though Russia has suspended its participation. Indeed, the treaty is still standing only because Biden quickly negotiated an extension during his first weeks in office, and the administration has expressed continued interest in strategic arms control if it can find a willing partner in Moscow.

The Biden administration has also worked to stabilize relations with China, a country whose nuclear arsenal is undergoing a rapid expansion. After a rocky start, Biden’s relationship with Xi Jinping has defrosted a bit, and the two countries have restored military-to-military communications. These actions make it less likely that a crisis between the two states could escalate into a war that would inevitably entail nuclear risks.

Biden also deserves credit for bolstering the U.S. nuclear umbrella, an important non-proliferation tool. The administration has strengthened NATO through its leadership regarding aid to Ukraine. It has also fortified the defense relationship with South Korea through the Washington Declaration, which will engage the two countries more closely on nuclear deterrence matters.

What Biden might do on nuclear policy if reelected

As with Trump, Biden’s first term in office provides useful guidance as to his likely nuclear policy priorities were he to be reelected. A second Biden administration surely would continue focusing on strengthening the alliance relationships that undergird the U.S. extended deterrent and on stabilizing interactions with nuclear-armed adversaries. For example, Biden seems likely to continue to seek to deepen U.S. ties to NATO, Japan, and South Korea, while also working to maintain lines of communication with Russia and China. Perhaps most important, Biden seems likely to carefully manage nuclear risks in the event of a serious crisis erupting with a nuclear power, for example over Taiwan, Ukraine, or the Korean Peninsula.

The Biden administration also seems likely to try to salvage some form of arms control when New START expires in 2026. Whether it will actually be able to do so, especially in the form of treaty-based limitations or reductions, is questionable. Russia has already suspended its participation in the treaty, and the rapid growth of China’s arsenal raises serious questions about whether bilateral, treaty-based U.S.-Russian arms control is even the right approach. But the administration seems likely to at least attempt to engage in less formal risk reduction measures with both countries, with an eye toward reducing the likelihood of misperception and miscalculation. Overall, Biden is likely to remain committed to a strong U.S. nuclear deterrent while seeking to carefully manage the escalation risks inherent in such an enterprise.