China is improving their ability to grab islands in the East China Sea that Japan formally owns:
China has responded to Japanese efforts to defend the Senkaku Islands by building a helicopter base on a Chinese island 335 kilometers from the Senkakus, This is within range of transport helicopters that could bring in troops and weapons in under two hours. This is seen as a response to the Japanese decision in late 2014 to purchase 17 American MV-22 transports. This the Japanese did to defend the Senkaku Islands from possible surprise Chinese attack. The V-22s are faster than helicopters but Japanese territory is about a hundred kilometers farther away than Chinese land. So given sufficient warning the Chinese and Japanese occupation forces would arrive on the Senkakus at the same time.
I said that preparing for a race with China to the islands is foolish.