The Nuclear Trilemma in Ukraine
Torn between different priorities and nuclear risks, Europe is currently sleepwalking into a long war in Ukraine.
A reckless, authoritarian, and nuclear-armed Kremlin leader ensures that there are no good solutions for the Ukraine crisis. Faced with inbuilt nuclear risks, Western states are trapped in a policy trilemma: abandoning Ukraine, humiliating Russia, or waging a forever war—all three options could not only have negative global repercussions, but might lead to nuclear weapons being used, even though the Russian leadership has recently toned down its nuclear rhetoric.
Currently, two heavily abridged corners of the trilemma dominate the public debate: those who would push Kyiv toward concessions claim giving in to Moscow would reduce nuclear risks, while those who would help Ukraine defeat Russia argue that the risks of nuclear escalation remain remote. Not only do these oversimplifications downplay each option’s inherent risks, but it is in fact the trilemma, with its unsavory trade-offs, that has been driving Kyiv, Moscow, and the West toward an unsatisfying compromise—the least bad option available, but one that still requires decisive political action to be achieved. With nothing suggesting such decisiveness, Europe is currently sleepwalking into a long war.
At the trilemma’s first corner are the dramatic strategic consequences of a successful Russian conquest. If the West abandoned Ukraine, a great power war of aggression behind the nuclear shield would become the name of the game. In Asia and in Europe, the United States’ alliances would become strained. Over time, they might even splinter. Add China’s ambitions, the US’ repeated bouts of isolationism, and a long list of transnational problems, and the current rules-based order would come under severe pressure.
Insecurity would spur political instability, economic depression, and armed conflict. The role of nuclear deterrence would grow. Proliferation would become harder to stem and rules enforcement would wither. Nuclear crises would become more probable. In the short term, appeasing Russia might indeed be the least-escalatory option for the West. In the medium-to-long term, it is fraught with uncertainty and could entail dramatic consequences.
Between a Quick Defeat and a Long War
In the second corner are the more acute nuclear risks of quickly and decisively defeating Russian President Vladimir Putin’s armies, enabling Ukraine to take back what is rightfully hers. From the Kremlin’s perspective, such losses might seem impossible to explain away to Russian citizens and to square with Putin’s imperialist ideological ambitions.
Losing Crimea would also have severe implications for Russia’s regional power position. Moscow’s friends in Damascus, New Delhi, or Beijing might run for the hills, while Western sanctions would continue to diminish the country’s economic potential. Putin’s entourage could lose trust in its leader and a palace coup would not come as a surprise. Faced with developments that could lead to his disposal, Putin might be ready to use nuclear weapons to signal his stakes and resolve.
The costs for Russia would be immense, but to him personally, given the potentially fatal alternative of regime change, they might seem palatable. In contrast to Putin’s hardly plausible current nuclear rhetoric, his threats would suddenly become credible. If believed, they would likely force a Western stand-down as the stakes do not appear to warrant a nuclear show-down. If misread, they could lead to actual use, with dramatic consequences for the international system.
The trilemma’s last corner is the least appealing: A long war that causes huge losses of life, costs, and commits the Kremlin and the Russian society to victory or bust. A Great Patriotic War type effort seems unconceivable today—but so did mobilization a few months ago. With time, Moscow’s limited initial investment in the war might give way to an embittered fight to justify the many dead, the broken economy, and the torn society. Russia’s people would likely see their fortunes tarnished and come to resent their leaders.
On the one hand, war might make Russia a much more militarized and dictatorial society, with Putin’s power expanded and dissent squelched. On the other hand, revolution would unavoidably be in the air—or at least on the leadership’s mind. Putin would see few solutions beyond winning or leaving. At that point, nuclear coercion against Ukraine and escalation toward NATO would be plausible, and both the West and Kyiv would be fools not to look for an alternative solution.
War, the Realm of Uncertainty?
As the future is notoriously hard to predict, the trilemma presents risks, not certainties. The global order could survive the weight of nuclear-shielded aggression. So far, American power, as the basis of the current system, remains dominant, and many still cherish existing international arrangements. It is also conceivable that a long war “only” destabilizes and impoverishes Europe without precipitating the use of nuclear weapons.
Most importantly, Putin might manage to stay in power even after losing Crimea—as the former Iraqi leader, Saddam Hussein, did after failing to conquer Kuwait and sacrificing hundreds of thousands of young Iraqi lives. Internally, Putin could suppress challenges to his rule. Externally, he could rely on nuclear deterrence while rebuilding his badly damaged armed forces. In this scenario, he might deem nuclear use neither worth his stakes nor conducive to his goals. Also, as a man in pursuit of an empire, it is at least possible that Putin might put his nation’s fate before his own, and step down without exercising all his options. Like the Soviet war in Afghanistan, this conflict might not cross the nuclear threshold either.
These alternative scenarios notwithstanding, the trilemma’s risks are real and pressing on all three corners at once. Consequently, over the coming months, this trilemma’s trade-offs will continue to drive Western decisionmakers toward an unsatisfying half-measure: Supporting Ukraine with arms and money, but avoiding a rapid and dramatic Russian defeat, all while hoping that this outcome will be sufficient for both Moscow and Kyiv to accept a compromise and avert the long war.
Risking a Perpetual Warzone
This is a terribly difficult needle to thread. It requires decisive action now—mighty sticks and real carrots. In particular, the West would need to provide more and better weapons, enabling Kyiv to achieve military results that would strengthen its negotiating hand. With any luck, the Ukrainian battlefield success might help to convince Moscow of the futility of further escalation.
More importantly, Western action would have to entail a massive commitment toward reconstructing Ukraine, the much-touted Marshall Plan 2.0, so that the government in Kyiv can sell the unsatisfying compromise at home—and so that Russia realizes that the West is willing to pay to defend its order.
And yet, during the last eight months, such foresight and determination have been rare. In Europe in particular, domestic politics, economic concerns, and bureaucratic inertia have often weighed heavier than strategic considerations. Therefore, sleepwalking into a prolonged conflict is a non-trivial possibility. The internationalist factions will continue to ensure that the West does not abandon Ukraine; the proponents of restraint will make certain to avoid a swift Russian defeat.
But without decisive political action, more of the same will lead to the trilemma’s third corner—the long war. This approach allows for temporarily avoiding hard choices and short-term risks. Yet a protracted conflict could not only lead to nuclear use, but would most likely transform Russia into an even more volatile neighbor, turn the continent into a perpetual warzone, and diminish Europe’s role in the world. This is in nobody’s interest—and yet it is the likely outcome.
Liviu Horovitz is an associate in the international security research group at the German Institute for International and Security Affairs (SWP) in Berlin.
Anna Clara Arndt is research assistant at the SWP.
Lydia Wachs is an associate in the international security research group at the SWP.
N.B. An earlier version of this article included a historical analogy to the Vietnam war, which caused misunderstandings. It was therefore amended (November 12, 2022).