Extended deterrence in Northeast Asia faces an unprecedented credibility crisis as nuclear multipolarity forces US allies toward once-unthinkable nuclear futures.
Both South Korea and Japan are debating military options to counter authoritarian strategic threats and to compensate for waning US security guarantees as China and North Korea expand their arsenals.
Allied nuclear hedging reflects hard projections. By the mid-2030s, China’s theater nuclear dominance could render extended deterrence operationally meaningless.
A tripolar nuclear order would give China escalation dominance in theater forces. Given deployment lag times, decisions to pursue indigenous strategic capabilities must be made soon.
Korean strategic thinking has crystallized into a tripartite logic: the alliance remains vital, extended deterrence is unreliable and nuclear independence may become necessary. Tokyo’s reconsideration mirrors Seoul’s calculus, pointing to the need for serious allied coordination on nuclear contingencies.
While the allies differ on managing Taiwan and North Korea, they have little option but to forge closer bonds against multiple nuclear adversaries and shifting US priorities.
Trump’s transactional approach compounds pre-existing doubts about US nuclear guarantees. Questions about credibility predate Trump and extend beyond Asia, but mixed messaging fuels suspicion that Washington will backstop allies with nuclear weapons. The White House appears reticent to repeat that any North Korean nuclear use would end the regime.
Japanese elite debate has moved from taboo to contingency planning, though public opposition remains substantial. Beneath intense diplomatic engagement lies an increasingly explicit expert debate driven by uncertainty rather than ambition.
Revising Japan’s three non-nuclear principles would establish the groundwork for rapid weaponization should deterrence fail.
China’s alarm at Japan’s possible nuclear awakening reveals proliferation anxieties now cut both ways. A recent Chinese report branding Japan a “potential nuclear threat” signals real trepidation that proliferation may soon extend beyond North Korea, with consequences that Beijing cannot control.
Meanwhile, Seoul confronts a starker dilemma. North Korea’s designation of South Korea as its principal enemy carries far greater weight if confidence in the nuclear-armed United States erodes.
Estimates of Pyongyang’s arsenal hinge on uncertain assumptions about weaponization of its growing fissile-material stockpile, which is one reason why KIDA’s Lee Sang-kyu assesses the force as already in the triple digits, not the roughly 50 often cited.
That uncertainty underpins arguments for a South Korean “nuclear-ready” option as former foreign minister Song Min-soon contends in his book, “Good Fences, Good Neighbors.”
Additionally, China’s expanding power looms in the background, while North Korea’s deepening partnership with Russia adds a strategic wild card neither Washington nor Seoul has fully reckoned with.
President Lee Jae-myung’s strategy of bolstering ties with Japan while balancing China reflects a desire to substitute insurance for lack of US assurance. But insurance may eventually require indigenous capabilities beyond Seoul’s three-axis defense system for defense, preemption, and punishment.
Korean planners doubt that Trump has North Korea top of mind, a skepticism that is accelerating Seoul’s transition toward self-reliant deterrence. That perception reinforces the consensus that South Korea must operate as a do-it-yourself fighting ally, making expedited modernization and wartime OPCON transfer practical necessities.
Greater Korean self-reliance doesn’t mean alliance rejection. It means recognizing that credible deterrence requires sufficient conventional forces (including a nuclear-powered submarine) and industrial capacity, with nuclear weapons as a contingency of last resort.
Prospective adversaries will not see it that way, and they may resort to diplomacy as an immediate response. Thus, the gravest near-term risk lies not in proliferation but in premature Trump-Xi or Trump-Kim summitry trading alliance credibility for vague promises of strategic stability or illusory denuclearization.
Xi wants stability so China can achieve political ambitions without fighting; Kim wants regime survival through acceptance as a nuclear power, free from sanctions and facing a weaker alliance. Summits ignoring these realities would repeat past failures amid a period when allies face serious trade-offs.
The Indo-Pacific’s emerging nuclear reality of multiple adversaries, anxious allies and a constrained defense industrial base requires abandoning both deterrence orthodoxy and diplomatic wishful thinking. Allies must generate real military and industrial power, while the US confronts that rebuilding its defense industrial base will take years.
Averting allied proliferation requires unglamorous alliance strengthening. Credibility is built by power that can actually be used, not weapons held in reserve, and this requires coordinated conventional buildups in counterforce missiles, autonomous systems and a far greater capacity for defense production.
The question is not whether Seoul or Tokyo pursues nuclear latency to shorten timelines to a bomb, but whether Washington can mobilize conventional capabilities to forestall that decision.
All three democracies should accelerate conventional capabilities to sidestep that reckoning as long as possible. But they should no longer shy away from debating it either.
Patrick M Cronin is Asia-Pacific security chair at the Hudson Institute and scholar in residence at Carnegie Mellon University’s Institute for Strategy and Technology (CMIST).