Even without having been used yet, nuclear weapons have shaped the war in Ukraine—and its outcomes will shape our views of nuclear weapons for years to come. The power of nuclear deterrence has added to the destruction that Russia has inflicted on Ukraine while reducing the chances that conflict will spread into NATO territory.
For now, Russia and NATO are effectively deterring each other—to some degree—while Ukraine is caught in between. NATO countries are acting more cautiously than they would be if Russia were not nuclear-armed. It’s tricky to measure this effect, or to separate the influence of nuclear weapons from fear of a wider conventional war, but it’s present, nonetheless. Yet deterrence is neither as stable as some strategists insist nor as easy to escape as some disarmament advocates hope.
Nuclear weapons have not deterred NATO countries from openly and heavily arming Ukraine or from imposing harsh sanctions on Russia and furthering its international isolation. As Russia’s violence against Ukraine continues to increase, so will NATO’s support to Ukraine, as well as public pressure for direct intervention. Some Western voices are already arguing that NATO has allowed itself to be too cowed by Russian nuclear threats, not just in ruling out direct military action but by avoiding some showier measures, such as the proposed transfer of Polish MiG-29 aircraft to Ukraine.
Wherever the war goes from here, it’s clear that nuclear deterrence is not automatic or inherent to the mere possession of nuclear weapons. It does not exist unless the other side believes there is a real, credible chance you would use the weapon. And credibility, as we can see in this war, depends on the stakes at play and the appetite for risk of the actors involved.