While contingencies involving North Korea’s ballistic missiles and Russia were among the scenarios the defense ministry explored, the top three all involved a crisis in the East China Sea. The first scenario examined a war between China and Japan over the disputed Diaoyu/Senkaku islands in the East China Sea. Earlier on Tuesday Japan summoned the Chinese ambassador in Tokyo for the first time since Shinzo Abe was sworn in as prime minister to protest the continued presence of official Chinese ships in waters around the islets, which are claimed by Japan, Taiwan and China.
The second scenario, meanwhile, expands on a Senkaku contingency and looks at a widening war involving PLA attempts to seize the Ishigaki and Miyako Islands west of northern Taiwan.
The third, and perhaps most controversial, scenario focuses on how Japan would react to a Chinese invasion of Taiwan in 2021