China Patrols Japanese Waters in the East China Sea

On Sunday, in a role-reversal of U.S. and allied naval assets probing China's maritime claims in the China Sea, two Chinese patrol vessels were sighted entering Japanese territorial waters in the Senkaku Islands.

While China has strongly objected to any presence of other nations' vessels or aircraft near its island construction projects in the South China Sea, its forces have frequently conducted patrols in the Senkakus. This latest is among dozens of recorded instances this year alone, and Japan suggests that Chinese government vessels enter its territorial waters in the island chain from four to 28 times a month, with near-daily approaches.

China and Tawain both also claim the islands, which they call the Daioyus; the chain is occupied and administered by Japan.

Sunday's patrol comes shortly after media reports revealed that Tokyo plans to reinforce a string of island military installations through the East China Sea, with outposts reaching nearly a thousand miles from the Japanese mainland to Taiwan.

The islands, including the Senkakus, will be fitted with missile batteries to allow Japan to deny transit to and from the Western Pacific, hemming in northern China and forcing warships and aircraft to detour far to the south. Additionally Tokyo will double manpower on the islands to 10,000 in total.

In November, Japan announced discussions with the island prefecture of Ishigakijima regarding the deployment of hundreds of additional troops, to be stationed on Ishigakijima for deployment elsewhere on the Senkakus in the event of an attack. A base on Yonaguni for 150 troops and additional installations on Mikayojima and Amami-Oshima are already in planning or construction.

A series of boat collisions in 2010 increased tensions in the Senkakus as Chinese-flagged vessels had literal run-ins with Japanese Coast Guard patrol ships. In the most dramatic instance, the captain of a Chinese trawler was arrested after colliding with two Japanese government vessels in the same day.