Caitlin Talmadge writes,

"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."

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July 8, 2024, Brookings