Japan is expanding its military presence on and around Okinawa by building a radar station on Yonaguni Island. This is westernmost inhabited Japanese island, although it only officially became part of Japan in 1879 (along with Okinawa). Yonaguni island has a population of 1,500 and is a favorite tourist attraction for Japanese. The island is 2,000 kilometers southwest of Tokyo, 505 kilometers west of Okinawa, 300 kilometers southeast of China, 110 kilometers east of Taiwan (which China claims) and 144 kilometers southwest of the disputed (with China) Senkaku Islands. This new radar station produced a very loud protest from China who are not happy with Japanese hostility to Chinese threats over the Senkakus.
The Japanese are becoming more alarmed at increasing Chinese military activity in waters and air space around Japan. It’s not just disputed areas, especially the Senkaku Islands, but around Okinawa and increasingly east of Japan, in the Pacific. Operating out there is what the Chinese would have to do for a blockade of Japan. As a result of all this Chinese naval and air activity there is growing support for expanding the Japanese military, especially obtaining long range UAVs for maritime patrol and ballistic missiles for hitting Chinese bases in the event of hostilities. This doesn’t bother China as much as constant Japanese chatter about developing nuclear weapons. But the Chinese believe that decades of anti-nuke militancy would prevent Japan from actually going down this road. If Japan did build nukes, it would make Japan once more dangerous to China and that could cause a really dangerous situation.
Back in 2012 China became particularly angry after the Japanese government purchased the Senkaku islands from the Japanese family that had owned them since the 19th century. China and Japan were also increasingly sending small warships to patrol contested parts of the disputed Diaoyu (in Chinese) Islands (Senkaku in Japanese and Tiaoyutai in Taiwan). The islands are actually islets, which are 167 kilometers northeast of Taiwan and 426 kilometers southeast of Japan's Okinawa and have a total area of 6.3 square kilometers. Taiwan also claims the islands, which were discovered by Chinese fishermen in the 16th century, and taken over by Japan in 1879. They are valuable now because of the 380 kilometer economic zone nations can claim in their coastal waters. This includes fishing and possible underwater oil and gas fields. For China, the islands are a valuable source of fish, which Chinese fishing boats taking over 150,000 tons a year from the vicinity of the Senkakus. China fears that Japan might try to prohibit Chinese fishing in the area. A conservative Japanese political group built the lighthouse in 1986, to further claims of Japanese ownership. Currently, the Japanese have the most powerful naval forces in the region, and are backed up by a mutual defense treaty with the United States. China was long dissuaded by that, but no more. China is no longer backing off on its claims, and neither is Japan. So these confrontations are becoming more serious. Taiwan is not considered a serious contender in this dispute, but is showing up anyway.
China also has claims on Okinawa, but the Chinese government has not become aggressive about this yet, as they have with claims on Indian territory. Back in 2010 Responding to Japanese media reports of menacing Chinese warships off Okinawa, China announced that these were Chinese navy ships engaged in training in international waters. Nothing special. Just training. Trust us.
Most Japanese don’t trust China. There has been growing evidence in the last decade that distrust is warranted. Back in 2004, for example China admitted that the submerged submarine the Japanese navy has been tracking off the coast of Okinawa was, indeed, a Chinese boat. The Japanese had always insisted that the sub was Chinese. Apparently, American P-3 patrol aircraft, operating from Guam, were the first to pick up the location of the Chinese sub and then turned the tracking over to the Japanese navy. It was American technology that confirmed the identification of the sub. During the Cold War, the United States developed techniques for identifying individual submarines according to their shape, and by the noises they made. The American navy maintains electronic databases of submarines "signatures." China apologized for the incident, which had their boat inside Japanese territorial waters for a short period of time. China said the cause was a navigational accident. China has been sending its subs to see more often since 2000 in order to raise the skill levels of the crews.