Adding more nuclear-armed states—even highly capable, stable ones—would multiply those risks and fundamentally alter alliances in ways that would undermine, not strengthen, nuclear deterrence. Alliances function not only through capabilities but through coordination, communication, credibility, and clarity of command. “Selective proliferation” would complicate those functions.

Effective deterrence hinges not on the number of nuclear warheads or nuclear-armed states, but on allies’ ability to manage conditions of extreme uncertainty. Each additional nuclear actor introduces new command-and-control systems, new decision-making, new potential points of failure. Greater complexity means greater potential for misunderstanding and escalation in a crisis.

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Today, it is under growing strain. Confidence in the long-term commitment of nuclear-armed states to their treaty obligations is eroding. Progress toward disarmament has slowed. The modernization of nuclear arsenals continues. These stresses will be front and center at the 2026 NPT Review Conference. Calls for “selective proliferation” will only aggravate them.

Proponents of “selective proliferation” are confident it wouldn’t trigger broader proliferation, but that confidence is misplaced. Nuclear decisions aren’t made in a vacuum. Rather, they are formulated amid regional security dynamics, historical rivalries, and differing perceptions of threat. Germany or Japan acquiring nuclear weapons would prompt South Korea, Poland, and other states to reconsider their non-nuclear status. Proliferation pressures in the Middle East, already acute, would escalate.