The Broken Nuclear Umbrella

For decades, American allies in Asia and Europe have relied on U.S. extended nuclear deterrence for their safety. They forswore acquiring their own nuclear weapons, agreeing instead to live under the protection of the United States’ nuclear umbrella. This arrangement worked during the Cold War because the stakes of that competition were so high that the United States could credibly—if just barely—say that it would wage nuclear war, even at catastrophic risk to itself, to prevent the conquest of its allies.

But the world that created the U.S. extended deterrence system is long gone. The United States retains important interests in Europe, but Russia’s threat is far more limited than when the Soviet Union was poised to conquer much of Europe and Asia. A war today would be about the precise boundaries of Moscow’s influence in eastern Europe, not the global balance of power. Similarly, the Korean Peninsula was once a battleground for rival Cold War blocs; today, that conflict is largely local, with Pyongyang desperately seeking to hold on to its power. And the Trump administration’s view that the purpose of alliances is first and foremost to enhance the United States’ core national interests is at odds with promises to jeopardize American cities to defend allies. In a world in which wars are largely regional and Washington is pulling back, it strains credulity to believe that the United States would wage nuclear war for faraway allies.

U.S. allies are thus increasingly worried that the extended deterrence system is now a bluff. Their fears are justified. Leaders in Latvia, Poland, and South Korea cannot be confident that the United States would risk its own destruction for their safety. Those in North Korea and Russia may be drawing the same conclusion. If Washington’s nuclear commitments are no longer credible, U.S. allies need new arrangements to ensure their most critical security needs.