"Seen in realist terms, then, China's maritime rise threatens to degrade Japan's strategic position in the region.[…]. A precipitous decline in conventional U.S. military capacity in the theater could have major diplomatic ramifications, undercutting American staying power in the western Pacific, giving rise to Japanese fears of abandonment, and unsettling the entire Asian security architecture. More to the point, Tokyo would likely interpret such a decline as foreshadowing an end to the American nuclear guarantee. Accordingly, an effort to discern, as through a glass darkly, Tokyo's nuclear options and their likely consequences is not only worthwhile but imperative for analysts and practitioners of Asian affairs. First, we briefly consider the motives that would induce Japan's leadership to make such a radical break with the antinuclear sentiments of the postwar era. Second, we consider the prospect of Japanese 'nuclear hedging,' an approach under which Tokyo would build up a capacity to develop nuclear weapons, keeping its strategic options open while remaining in formal compliance with its commitments under the Nuclear Non-Proliferation Treaty, or NPT. Third, we consider the technical feasibility of a swift Japanese nuclear breakout, paying particular attention to assumptions that Tokyo could stage a breakout within a year of deciding to do so. Fourth, we identify possible force structures and strategies available to Japan should the island nation's leadership indeed decide it is in the national interest to cross the nuclear-weapons threshold."
Naval War College: http://www.usnwc.edu/
Naval War College Review (Summer 2009), v.62 no.3, p.59-78