For now the Chinese military wants to avoid armed conflict over the islands . . . but its longer-term goal is to pressure Japan to give up its administration of the islands. That would give China a break in what is known in China as the ‘first island chain,’ a string including the Diaoyu, that prevents China’s growing ballistic submarine fleet from having unobserved access to the Pacific Ocean. Taiwan is part of the ‘first island chain,’ as are smaller islands controlled by Vietnam and the Philippines.
As Perlez goes on to point out, the presence of armed Chinese and Japanese fighter jets in the same airspace greatly increases the chances of a mistake leading to a serious conflict. This is a fast-moving story, and one that greatly increases the difficulties for American diplomacy.