New Delhi, Dec. 16 -- The recent Sino-Japanese tensions over Taiwan, coupled with Prime Minister Takaichi Sanae's comments on defending the island, reflect an underlying power struggle that has long existed but has largely been managed through conventional norms and strategic ambiguity. With her remarks, however, the buck stops with Takaichi.

She has done what no Japanese leader before her has openly dared to do: publicly state that Japan's own security and national survival are inseparable from the fate of Taiwan. In doing so, Takaichi articulated a strategic truth that has long been whispered and tacitly understood in Tokyo, Washington, and even Taipei, but rarely acknowledged openly for fear of upsetting established norms and unspoken...