Missile threats. Terrorist attacks using biological and chemical weapons. Mass hostage-takings. Foreign special operations infiltrations into territorial waters. State-sponsored kidnappings of Japanese citizens. And multiple neighboring autocratic regimes developing nuclear weapons. These are some of the many national security challenges Japan has faced in the two decades after the end of the Cold War. Japan's basic defense strategy through the 1980s, called hoppo jushi or "emphasis on the northern region," aimed to develop a basic military capability to defend the archipelago from a possible...