A Chinese coast guard vessel first entered Japanese territorial waters around the Senkaku Islands, which China calls Diaoyu, in December 2008. The Japanese government has assumed that the commander of the vessel acted on his own initiative.

 

Yu Zhirong, who was an officer on the vessel when it entered Japanese waters on Dec. 8, 2008, told Kyodo News that an order came directly from the central government based on a plan devised since 2006 to regularly send patrol ships to the area.

 

China decided to step up maritime activity around the Senkakus after a Japanese patrol vessel and a Taiwanese ship collided near one of the uninhabited islands in June 2008, Yu said.

Taiwan also claims the islands, which it calls Tiaoyutai.

 

China began sending patrol vessels to the Japanese territorial waters more frequently as tensions between the countries grew following the collision of a Japan Coast Guard ship and a Chinese trawler in September 2010.

 

Tensions escalated after Tokyo brought the Senkakus under state control in September 2012, resulting in the biggest flare-up of Chinese public anger toward Japan in years.