This topic is a far cry from my typical interests and experiences. It has been a topic in my mind and in my conversations, though I feel more a student of the topic than a teacher. I am writing this article because I have not seen anyone else do so. Please convince me I am wrong.

Since the US dropped an atomic bomb on Hiroshima, nuclear weapons have been a singular force shaping relationships between nations. The first atomic age was a race to build and stockpile nuclear weapons, with many countries choosing alliances with nuclear powers like the US in lieu of building their own. The second atomic age was characterized by disarmament because the US and USSR thought fewer weapons would reduce the chance of a civilization-ending nuclear holocaust. The USSR’s dissolution would accelerate the need for disarmament. The newly formed eastern European governments were ill-prepared to control a stockpile and were encouraged to return them to Russia or disable them. With Trump’s second electoral victory, we are entering a new atomic age: proliferation.

US citizens’ decisions have weakened the US security guarantee. The guarantee was created to try to prevent another world war. The security guarantee states that a war against one is a war against all, requiring a response of the allies’ choosing. Americans and free Europe believed such a guarantee would deter a power-hungry authoritarian like Hitler or Stalin from conquering their neighbors. To be credible, it must include potential nuclear strikes by the US against an invading force. Though still sharing security guarantees with the US, the United Kingdom and France each developed a domestic nuclear strike capability for different reasons, though the common thread is that their quantities are intended to deter an invading force rather than to completely annihilate any aggressor nation. Only the US and USSR developed that capability. The mutual defense guarantee has been a constant of US foreign policy since World War 2, regardless of the party in power. Every new president from 1946 until 2016 endorsed the mutual defense guarantee, until Trump’s first administration refused to endorse it. Trump accused the other countries of failing to meet their defense spending obligations in order to fund their generous social services i.e. freeriding on American defense spending. This accusation put a spotlight on an open secret. Allies believed the accusation was a negotiating tactic rather than a dissolution of the security guarantee, but calling it into question added uncertainty to a policy that requires certainty to work. By electing Biden in 2020, US citizens effectively chose to endorse the security guarantee, sending a message to allies that they would not be left to fend for themselves. Since then, Trump has debated going beyond de facto withdrawal from the treaty and officially withdrawing from the alliance. With his re-election, Americans have sent the opposite message. Vacillating every four years creates a strategic ambiguity of what the US would do in a conflict. This position shifts the US from an iron-clad mutual defense of the free world to “fuck around and find out”. The ambiguity of alliances returns us to a world closer to the conditions that created World Wars I and II. A rational actor should discount the guarantee, knowing Americans might not commit to deter a war but may show up late and prevent total subjugation. There are precedents: WW I, WW II, Korea, and a disastrous attempt in Vietnam. Regardless, a rational actor should work towards securing their own countries.

If you believe these countries have an interest in nuclear weapons, the next question is if they can credibly build them. Again, North Korea has nuclear weapons, and Iran is developing them. Neither developed them from first principles; North Korea was given assistance by the USSR and Iran, sanctioned by most of the world, is presumably receiving assistance from North Korea. If these isolated countries can obtain and maintain a nuclear arsenal, most advanced countries in Europe, the Middle East, and Asia could easily follow suit. The most challenging part is obtaining fissile material e.g. uranium or plutonium. That material must be enriched with hundreds of centrifuges, which would be a trivial task for many countries with both nuclear power plants and an advanced manufacturing base. Countries like the Netherlands, Germany, Japan, and South Korea have long had the capability to build these weapons. What they have not had is a reason to fear for their security, until now. Arguably, building a domestic industrial base for nuclear weapons is easier than trying to build the industrial base required to master the kind of warfare seen in Ukraine, but I will save that for another post.

A world filled with nuclear weapons and fewer alliances is potentially safer, but I would not bet on it. Some scholars believe if everyone had nuclear weapons, no one would attempt to conquer another out of fear of a retaliatory strike, especially if the defending country felt that they were on “death ground” i.e. they had no option to surrender and live in peace, only fight or die. This equilibrium only makes sense if each country can secure a quantity of weapons to deal with any threat, which seems implausible for smaller eastern European countries trying to defend against a Russian invasion. Worse, breaking the so-called nuclear taboo by unleashing a nuclear weapon to defend oneself could invite a nuclear response that still escalates the situation, potentially outright killing everyone in the country. It may not even be by the host aggressor. For example, I worry greatly about a subjugated Ukraine, where Russia enslaves the population and forces anyone capable of holding a rifle to march into Poland to fight for Putin’s glory. With a nuclear weapon, who would Poland fire against? Ukraine or Russia? These are the fears of the Cold War, and they are returning to a more fragmented world. Nuclear weapons could simply disappear, being quietly traded between countries. Official or unofficial authorities could sell nuclear weapons for their own profit. Governments with weak institutions could fail to prevent rogue groups from taking control to use towards their own ends. The failure modes are plentiful, and the more nuclear weapons circulating, the greater the chance for a mistake. Unlike the tit-for-tat logic of the Cold War, there may not be a nuclear holocaust scenario if there is no complex web of alliances, but there are still plausible escalation paths. For example, a defender uses nuclear weapons to defend themselves. The aggressor, telling the world the defender has broken the nuclear taboo, responds with an overwhelming nuclear salvo that destroys the country—then marches into their neighbor. How should the next defender respond? 

Such nightmare situations have no good choices, only some choices that are less bad than others. The least bad option now for other countries is to hope for the best from American security guarantees but prepare for the worst. France, to their credit, has attempted to preempt any European countries building their own weapons by floating a potential nuclear security guarantee to other European countries. Yet, countries are still likely to see to their own defense as many fall outside that guarantee or do not entirely trust French promises . Since the invasion of Ukraine, these countries have increased their defense spending as a percent of GDP, some nearly doubling the spending. It seems all but a foregone conclusion they would also pursue nuclear weapons programs.

Welcome to the third nuclear age. 

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Thanks to Andrew Miller, Kevin Kohler, and Emma McAleavy for reviewing drafts of this post.