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Paper short abstract

This paper analyzes Japan’s reliance on US nuclear deterrence despite Article 9. It argues the constitution acts as a “committee of restraint,” paradoxically enabling deeper conventional integration and “counterstrike capabilities” while precluding indigenous nuclearization amidst regional crises.

Paper long abstract

Japan presents a unique paradox: it is the only democracy to constitutionally enshrine pacifism (Article 9) while relying explicitly on another state’s nuclear arsenal for security. This paper investigates how Tokyo reconciles its anti-nuclear national identity with an escalating dependence on U.S. extended deterrence amidst a volatile regional environment marked by North Korean missile tests, China’s nuclear modernization, and the normalization of nuclear coercion following Russia’s invasion of Ukraine.

Drawing on alliance theory, two-level game analysis, and literature on the nuclear taboo, the study traces Japan’s security evolution from the “Three Non-Nuclear Principles” through successive crises to the watershed 2022 National Security Strategy. The analysis argues that Japan is pursuing a strategy of “maximizing extended deterrence under strategic ambiguity.” By leveraging interpretive flexibility within Article 9, Tokyo deepens security cooperation—such as real-time intelligence sharing and “counterstrike capabilities”—while maintaining domestic constraints that preclude public discussion of NATO-style nuclear sharing.

The paper highlights three key tensions: (1) credibility concerns regarding U.S. decoupling; (2) the ideological cleavage between the Hiroshima-Nagasaki anti-nuclear memory and conservative realism; and (3) the gap between public opposition to nuclear acquisition and elite moves toward contingency planning. Comparative analysis reveals that Japan’s trajectory diverges from Germany’s acceptance of nuclear sharing and South Korea’s mainstreaming of indigenous nuclear debates.

Ultimately, the study concludes that Article 9 functions not as an obsolete relic but as a domestic “committee of restraint.” Paradoxically, this constitutional constraint enables deeper conventional integration with the United States by reassuring neighbors of Japan’s non-nuclear intentions. However, this delicate balance faces mounting strain should the credibility of U.S. deterrence erode or a Taiwan contingency force a choice between constitutional principles and survival.

Keywords: Japan security policy, Article 9, extended deterrence, nuclear taboo, U.S.-Japan alliance, strategic ambiguity.