The Deterrence Ceiling:
Ukraine’s Postwar Security Under Russia’s Nuclear Shadow
by Cesar Jaramillo | September 12, 2025
European and allied leaders met in Paris last week to unveil what was presented as a foundational step toward Ukraine’s postwar security – a “Coalition of the Willing” pledging robust guarantees against future Russian aggression. More than two dozen countries committed to provide support through training, continued provision of weapons, and air, land, and sea deployments once a ceasefire or peace deal is in place.
Implementation details remain scant. Yet even if every pledge were fulfilled, the coalition would still encounter an immovable barrier in Russia’s nuclear arsenal. It imposes a ceiling that no amount of conventional firepower or political resolve can break. Even had Europe offered similar guarantees or spent far more on Ukraine’s defense earlier, it would still face the same reality: as long as Russia retains nuclear weapons, the prospect of nuclear war will always limit the scope and credibility of any security guarantees.
This is not to suggest that the coalition is meaningless. It demonstrates Western unity, reassures Kyiv, and signals to Moscow that Ukraine is not alone. Yet these positives must coexist with the fact that any attempt to push Russia too far against its strategic interests risks crossing thresholds that could trigger nuclear use. Russia is acutely aware of this dynamic and will continue to use the prospect of nuclear war to its advantage.
President Volodymyr Zelenskyy has argued that “thousands” of troops may be necessary to fulfill security guarantees. At the same time, President Vladimir Putin has warned that any Western troops deployed in Ukraine would be treated as legitimate targets. This is a chilling reminder of how quickly conventional deployments can collide with nuclear deterrence and heighten the risk of escalation.
After Russia’s annexation of Crimea in 2014, the prevailing assumption was that expanding military capabilities would deter further aggression. That assumption collapsed in 2022, when Russia launched a full-scale invasion, emboldened by the knowledge that its nuclear arsenal would limit NATO’s direct involvement, as indeed it has.
For Moscow, the issue is not only about formally keeping Ukraine out of NATO but also about preventing any NATO-style military footprint on its territory. Russia will predictably not accept de facto NATO deployments on its doorstep, even if framed as security guarantees, unless they are explicitly agreed to in eventual negotiations. Any plans that ignore this reality will either face limits in implementation or risk setting an escalatory dynamic in motion.
At the end of the day, the possibility that nuclear weapons might be used constrains how far Ukraine’s “Coalition of the Willing” can deter or respond, even if hundreds of billions are spent and dozens of nations pledge support. This is a grim reality that understandably upsets those who lament the prospect of impunity for Russia’s illegal invasion. Yet the fact remains: any actor possessing nuclear weapons can exploit them to shape the behavior of those determined to avoid a nuclear confrontation.
The only way to remove this strategic straitjacket is through the complete elimination of nuclear weapons. They are destabilizing not only if used, but also because the fear of their use constrains credible conventional responses and entrenches insecurity. Absent elimination, any security arrangement remains vulnerable to nuclear blackmail. In Ukraine’s case, that means unsavoury concessions will almost certainly need to be made.
Not long before announcing Ukraine’s “Coalition of the Willing,” NATO unveiled plans to raise defense spending to 5 percent of GDP by 2035. This is more than double the 1.3 trillion dollars that NATO members already devote annually to defense, a sum greater than the combined military spending of the rest of the world. Yet the same limitation applies: more spending may improve readiness and capabilities, but it cannot lift the nuclear ceiling.
Beyond the nuclear dimension, the tragic paradox is that a surge in military spending, unaccompanied by strategy or commitments to diplomacy and disarmament, will not deliver security. On the contrary, it risks creating the very conditions it claims to prevent. Adversaries will respond in kind, enhancing their own capabilities, forging tighter alignments, and seizing on the buildup as justification for endless increases in military budgets on both sides.
Since the war began, weapons, training, and financing have flowed with urgency, while serious efforts to outline a negotiating framework, reduce nuclear risk, or set the conditions for dialogue have been conspicuously lacking. What emerges is not stability but an entrenched arms race in which each escalation triggers the next and the prospect of negotiated restraint becomes increasingly remote.
More than three and a half years into the war, Europe and the broader international community still lack a cohesive, workable plan for how it might end. Many thousands of lives have been lost, billions of dollars spent, yet there is still no clear answer to the most basic question: what is the endgame? Is the objective to restore Ukraine’s 1991 borders, to weaken Russia, to compel negotiations, or simply to prevent Ukraine’s collapse? The absence of clarity leaves strategies adrift, reinforcing a cycle of improvisation in which immense costs are incurred and in which the risk of nuclear escalation may grow.
Ukraine’s security crisis is therefore more than a regional challenge. It is a testament to the futility of building order on nuclear deterrence. Coalitions, budgets, and guarantees may shift the tactical balance, but the nuclear shadow is immovable. And the irony is stark: the very deterrence doctrine Russia now exploits in Ukraine is the same one that the West continues to defend.
Cesar Jaramillo is Executive Director at SANE Policy Institute.