A turning point for nuclear deterrence

The rupture between Europe and Donald Trump’s U.S. over Greenland may be papered over in time, but Europe’s trust in the U.S. as a reliable North Atlantic Treaty Organization (NATO) ally has been irreparably broken. As the last remaining arms control treaty limiting Russia’s nuclear arsenal comes to an end, conversations about defending Europe are acquiring a sharper edge.

NATO came together in 1949 as a defensive nuclear alliance against the Soviet Union with the U.S. as its primus inter pares— the ultimate guarantor of the security of its western European members. Now, the hegemon has turned on its own alliance, over Mr. Trump’s desire to acquire Greenland, a sovereign territory under the jurisdiction of NATO member Denmark. Mr. Trump’s bullying and economic warfare has broken trust, and without trust NATO as a nuclear alliance is hollowed out. How Europe responds to this rupture will shape not only the future of the continent’s security, but also the future of conversations about nuclear deterrence. Depending on whether the new security architecture of Europe privileges nuclear deterrence, thinking about nuclear weapons will either be updated to reflect the lessons of the 80 years since a nuclear weapon was last detonated, or continue to echo conversations that took place when the Nuclear Non-Proliferation Treaty (NPT) separated the world into nuclear haves and have-nots.

The nuclear conversation

The intervening years since the NPT restrained horizontal proliferation have seen threats to world security shift from nuclear rivalry to terrorism and extremism; climate change; economic stress; inequality; and regional rivalries. While none of these is easily addressed by nuclear weapons, conversations about nuclear possession and use continue to privilege nukes as the ultimate guarantor of peace and security even as great power rivalry returns to the global stage.

Moreover, discussions about ‘what deters’ appear to have ossified. At the dawn of the nuclear age, when possessors were still building their arsenals, there was a debate on whether deterrence rested on certainty or uncertainty. Some believed that uncertainty was enough; that allowing an adversary to not be certain that any adventurism would not be countered with a nuclear response was enough for deterrence to work. A form of this deterrence arguably operated between India and Pakistan between the 1980s and 1998. Israel, with its opaque nuclear status, also relies on this uncertainty. For the rest of the nuclear possessors, a complex interplay of great power politics led to growing stockpiles and an emphasis on the certainty of a nuclear response. Testing demonstrated intent and number of weapons indicated resolve.

Yet, even as nuclear states were racing to stockpile warheads, a taboo on nuclear use was gaining strength. A nuclear weapon has not been deployed since 1945. While nuclear threats have been issued, and states have developed ever smaller and more ‘useable’ weapons (tactical or battlefield nukes), nuclear use, to the best of our knowledge, has never been seriously contemplated.

Arms control agreements between the U.S. and the Soviet Union/Russia, along with the global non-proliferation architecture may have contributed to sparing the world another Hiroshima, but thinking on nuclear deterrence remains essentially unchanged. And now, after a sharp reduction in nuclear stockpiles between the U.S. and Russia, the pendulum may be swinging back. 

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China, Russia and the U.S. are ambitiously modernising their nuclear stockpiles. China has reportedly added 100 warheads a year since 2023 to reach a total of 600. In 2015, the U.K. reversed a 2006 decision to reduce its stockpile and is at 225 warheads. The last remaining arms control agreement between Russia and the U.S. —New START — expires on February 5, and if both states start increasing their stockpiles from the current 5,459 and 5,277, respectively, it will send a clear message of moving back to Cold War ideas of deterrence. 

Lessons from Ukraine

The war in Ukraine should have led to a more serious debate about what deters. Russian President Vladimir Putin had made nuclear threats before his invasion and then again in October 2022. Yet those threats were countered not by the certainty of a nuclear response, but by the certainty of a robust response that left the nuclear element unclear. It is worth remembering that Ukraine — a non-nuclear country — has been able to defend itself against a nuclear adversary. Yes, it has had help and yes, it has lost territory, but Ukraine has not yet been defeated by its nuclear neighbour. 

Therefore, what happens in the next few months as Europe comes up with a security architecture that does not rely on the U.S could reshape nuclear thinking. 

Apart from some tepid discussion about how France and the U.K. might extend their nuclear umbrella to cover Europe, most of the previous debate appeared to return to hugging the U.S. ever closer. In the meantime, an ad hoc grouping of mainly European states, called the Coalition of the Willing, has come together to guarantee Ukraine’s security. Ukraine now has experience in defending itself against a nuclear state. Against this backdrop, whether Europe chooses to base its new security architecture on some sort of replacement nuclear alliance, or on a defensive alliance that may have a nuclear element, will shape future discussions about nuclear weapons and deterrence. 

Priyanjali Malik writes on nuclear politics and security.