► The nuclear non-proliferation regime was significantly undermined during the first Trump administration including the breakdown of the New START Treaty and the US withdrawal from the INF Treaty.

► Both the United States and Russia are increasingly unconcerned with stopping nuclear proliferation among their respective allies.

► The weakening international regime on nuclear weapons will return the world to the more dangerous period witnessed during the early Cold War which was devoid of many guardrails among the superpowers.

The election of Donald Trump to a second term in November 2024 is increasing concerns about the emergence of a New Cold War. The interconnectedness of the revisionist bloc has increased following Russia’s invasion of Ukraine with both North Korea and Iran openly supporting Russia militarily while China assists by increasing its purchases of Russian oil.

This grouping is also infamous for its nuclear weapons. While Russia and China are recognized nuclear weapons states in the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), North Korea and Iran have both illegally implemented nuclear weapons programs with the former having succeeded and the latter on the brink of building a bomb.

Over the previous several decades, this bloc has been at the center of nuclear non-proliferation challenges. Moreover, amid the changing world order, the first Trump administration added new challenges to the nuclear non-proliferation regime and many are concerned his reelection will further its breakdown. And discussions of the New Cold War are progressing alongside talk of a new nuclear arms race. What are the prospects for reversing this deteriorating trend in the possibility of nuclear war? And what are the consequences for the Korean Peninsula? Unfortunately, the outlook is grim on both accounts.

Cold War Arms Reductions Agreements Nearly Gone

Following the near outbreak of nuclear war during the Cuban Missile Crisis of October 1962, the United States and Soviet Union agreed to the Limited Test Ban Treaty and a Hot Line Agreement in 1963 to ensure communication in tense situations. From this beginning, the two superpowers gradually worked towards the signing of the NPT in 1968 and also bilateral agreements that limited the development and stockpiling of nuclear weapons such as the Strategic Arms Limitation Treaty (SALT) in 1972. In 1991, the two countries signed the Strategic Arms Reduction Treaty (START) which obliged them to begin dismantling the thousands of warheads they had developed during the Cold War. These and other agreements not only pointed the world towards the eventual goal of dismantling all nuclear weapons, but began to make real progress in that direction as well as initiate programs that could build trust and decrease the possibility of nuclear war.

However, since Donald Trump’s first term beginning in 2017, the relationship between the United States and Russia regarding nuclear weapons has deteriorated. While Trump is not solely to blame, his instincts have led to tearing up agreements while failing to negotiate new ones.

The best example of this tendency is the New START Treaty, which places limits on both countries’ number of deployed nuclear weapons. The Trump administration sought to renegotiate the treaty with Russia, but Russian refusals to do so nearly led to the treaty expiring. The Biden administration had to rush to renew the treaty immediately upon taking office. Now the agreement is set to expire in February 2026, and will have to be completely renegotiated as the single renewal option has already been exercised.

However, negotiating another round of START will be even more difficult now in the context of the Russian invasion of Ukraine. Russia has refused to allow verification of New START compliance since early 2023. Russian transgressions aside, it is unclear what the future of the a new nuclear arms control treaty would look like under the second Trump administration. If the second Trump administration insists on stricter terms that Russia rejected before it began its war against Kiev, there is little chance it will agree now.

The first Trump administration also withdrew the United States from two other important nuclear weapon-related treaties. In October 2018, the Trump administration announced it would leave the Intermediate-Range Nuclear Forces (INF) Treaty which banned ground-launched missiles with ranges between 500 and 5,500 km. This decision very recently had direct ramifications when Russia used an intermediate ballistic missile to attack Ukraine on November 21, 2024. The first Trump administration also withdrew the US from the Open Skies Treaty which allows countries to conduct unarmed overflights of countries to ensure they are not preparing for war.

To be certain, Russia reportedly violated both the INF Treaty and Open Skies Agreement long before the Trump administration decided to withdraw. But two of Trump’s own priorities will likely hinder any progress towards new agreements limiting the number or development of nuclear weapons.

First, Trump’s biggest priority terms of national security has always been China. A major reason why the first Trump administration failed to renew the New START Treaty with Russia was because Trump demanded that China join as well. Not only did Beijing refuse, but it is in the midst of a rapid nuclear weapon expansion and modernization program. The Biden administration pursued talks on nuclear weapons with China, but they broke down over US arms sales to Taiwan. Given Trump’s proposed China policy includes blanket tariffs and potentially expanding weapons sales to Taiwan, little progress is expected on arms talks with China and thus perhaps Russia as well if Trump continues to insist on trilateral negotiations.

Second, Trump has also prioritized modernizing the US nuclear arsenal. Trump promised in 2018 to build a “brand-new” nuclear force. Project 2025, a document produced by Trump allies to prepare for his second term, argues that the US “manifestly needs to modernize, adapt, and expand its nuclear arsenal.”

In other words, we are seeing a new nuclear arms race given the absence of treaties to limit the number of warheads and their delivery mechanisms and a lack of platforms to build trust and reduce tensions reminiscent of the early Cold War period.

Allied Proliferation Increasingly Likely

The understanding between the Soviet Union and the United States about restricting allied proliferation during the Cold War is also breaking down. The NPT was drafted by the two Cold War adversaries with the intent on limiting nuclear proliferation among their allies with the understanding that nuclear weapon use by American or Soviet clients could draw the two powers into a nuclear conflict.

Now, however, this norm is withering away. Russia is repaying Iran and North Korea for their assistance in the war against Ukraine by shielding the two countries’ nuclear programs at the UN Security Council. Earlier this year, International Atomic Energy Agency (IAEA) inspections found that Iran was on the brink of developing nuclear weapons given the amount of highly enriched uranium it possesses. Despite this finding constituting a violation of the Joint Comprehensive Plan of Action concluded between six major countries and Iran in 2015, Moscow has backed Tehran by accusing the US of not lifting sanctions as the deal outlined.

Similarly, earlier this year Russia vetoed a proposal for the UN Security Council to extend the “panel of experts” which monitors the implementation of sanctions against North Korea levied to limit its nuclear weapon and missile development programs.

On the flip side, many wonder whether the US will continue to uphold the norms of the NPT regime during Trump’s second administration. Trump’s transactional approach to alliances and his tendency to boast about his close relationship with North Korean leader Kim Jong Un helps fuel talk in Seoul about an indigenous nuclear program.

Moreover, it is quite possible the second Trump administration takes an ambiguous or even supportive position towards Seoul acquiring nuclear weapons. Former Secretary of State Mike Pompeo earlier this year was supportive of the idea. Elbridge Colby, long rumored to be a candidate for an important post in the second Trump administration, has also argued that Washington should not sanction Seoul if it were to build nuclear weapons while consulting the US.

Implications for South Korea

South Korea (and North Korea for that matter) now sit at the intersection of a three-way nuclear arms race between the US, China, and Russia. Increasing tensions and probability of nuclear war at the great power level will inevitably spill over to the Korean Peninsula as it did during the Cold War. Even if these tensions do not escalate into all out war, they can have very real and terrifying consequences; an example of this is the downing of Korean Airlines Flight 007 in 1983 amid a surge in tensions between the US and Soviet Union.

South Korea will be forced to contemplate the trade offs of supporting the liberal international order, the NPT regime included, which undergirds its economic development and international standing, and a realist calculation about self-help and survival in the face of increasing North Korean threats amid a possibly weakening US-ROK alliance, growing great power competition, and a nuclear arms race that is nearly devoid of guardrails. While much of the world hopes Seoul will follow the former path as it has done until now, few will probably blame South Koreans if they choose the latter route.