Both zones cover the islands called the Senkaku or Diaoyu (in Japanese and Chinese, respectively), which Japan controls but that are claimed by China, too. They also form part of the Ryukyu island chain, which is particularly sensitive as any hostile power must pass the islands on the way to the Japanese heartlands; they give Japan a lot of territorial sea space, and they might contain exploitable underwater gas and oil fields. Thus Tokyo intends to hold on to them by all means necessary.
