Nuclear deterrence has demonstrated its efficacy—so far. To grasp its workings, one need only examine the conflict in Ukraine. While America and Europe arm their ally, they refrain from deploying combat troops against Russia, which, in turn, refrains from striking at the West. This mutual apprehension ensures that nuclear powers abstain from overtly attacking each other, much like during the Cold War era when numerous proxy conflicts simmered. A testament to its success is the limited number of countries possessing nuclear arms—only nine, fewer than previously feared and fewer than those capable of manufacturing them.
As NATO commemorates the 75th anniversary of the signing of the North Atlantic Treaty this week, credit is due to the concept of “extended deterrence.” Through this mechanism, America has provided a nuclear shield for European and Asian allies, partly to contain adversaries and partly to dissuade allies like Germany, Japan, and South Korea from pursuing their own nuclear capabilities.
The prospect of Donald Trump returning to the presidency poses a significant threat to global stability, particularly in the context of the increasingly precarious nuclear balance worldwide. His stance of allowing Russia unchecked freedom in dealing with NATO allies who fall short on defense spending jeopardizes the trust essential for the viability of extended deterrence. Such a breakdown in trust could pave the way for the nightmarish scenario of widespread nuclear proliferation—a scenario the United States has long sought to prevent.
As the world’s pioneering nuclear power, the United States has historically endeavored to prevent the spread of nuclear weapons—a challenge often referred to as the “nth-country problem.” The proliferation of nuclear capabilities not only increases the likelihood of crises spiraling out of control but also poses constraints on American power, raising the specter of nuclear retaliation against the U.S. itself. To combat this, America has pursued an implicit “strategy of inhibition” comprised of norms and treaties, diplomatic coercion, and reassurance through military alliances and security guarantees.
The concept of extended deterrence, despite its counterintuitive nature—where the U.S. risks its own security to safeguard allies—has been a cornerstone of American foreign policy. However, doubts have persistently lingered. To bolster this commitment, the U.S. has stationed troops and nuclear assets in Europe while involving allies in nuclear missions.
Mr. Trump’s skepticism towards allies as assets rather than burdens has raised concerns, particularly as global tensions escalate. His unpredictable rhetoric and potential policy shifts threaten to undermine American security guarantees to NATO and allies at large. This uncertainty is compounded by suggestions from within Trump’s orbit of scaling back American commitments to NATO or adopting a “dormant” NATO approach.
European nations are grappling with contingency plans, including the possibility of pursuing their own nuclear programs if traditional security assurances erode further. While some advocate for Europeanizing NATO or relying on the nuclear arsenals of Britain and France, such measures are deemed insufficient in the face of evolving threats.
Ultimately, credible American deterrence remains indispensable for global security. A retreat into isolationism under the banner of “America First” not only emboldens adversaries like Russia and China but also erodes trust among traditional allies. The consequences of diminishing American power reverberate beyond national borders, amplifying nuclear risks on a global scale.