Japan is increasingly concerned about China’s growing military activity around the Japanese waters and airspace, and has significantly reinforced its defenses in the area, including remote islands that are key to Japan’s defense strategy. Japan is also worried about Russia’s military activity and their joint operations with China. Japan’s military said it dispatched a surveillance plane and a navy ship Tuesday after spotting a Russian submarine off the coast of a southwestern island near Taiwan.The submarine, accompanied by a Russian naval ship, was moving northeast between Yonaguni and the nearby island of Iriomote. It was the first sighting of a Russian submarine in those waters. Why is Japan so concerned about Taiwan ?

