At its heart, the squabble was not only about the Senkaku islands, called the Diaoyu by the Chinese, where the boat collision took place earlier this month. Instead, it was likely a message to other countries with which China has territorial disputes, particularly in the South China Sea. This week China showed that it is willing to go to extraordinary lengths to exert its maritime claims. Lately it has taken to calling the South China Sea, which it disputes with five of its South-East Asian neighbours, a "core national interest".