Objects in History are Closer Than They Appear

China's claims to Japan's Senkaku Islands magically appeared after it was discovered that resources might be around the islets. And the claims have been aggressively asserted after China's military capacity to contest control was developed. Face it, nobody near China is safe from newly discovered claims of ownership.

China used to acknowledge Japan's ownership of the Senkaku Islands (tip to The View from Taiwan):

A Chinese government document from 1950 appears to refute China's current claim to the Senkakus by indicating the islets are part of Japan's territory and referring to them by their Japanese name, a just-obtained copy revealed. ...

It was completed on May 15, 1950, about 7½ months after the Communist Party founded the People's Republic of China. Beijing now argues that the Senkaku Islands have been known as Diaoyu since ancient times, but this appellation is nowhere to be found in the document.

Like I said, nobody is safe.

China's neighbors need to speed up that military modernization. Standing still is no defense from this threat. Past Chinese territorial claims aren't extinct just because we don't seem them today. They're just dormant waiting to be brought back to life when the conditions are right.