Beijing's announcement of a new Air Defense Identification Zone over the East China Sea on Nov 23 has evoked an angry response from the United States and its principal East Asian allies, Japan and the Republic of Korea. On Dec 17, US Secretary of State John Kerry said that Washington will not recognize China's ADIZ.

Some observers might fault the Chinese government for not fully discussing the plan with the affected countries before making the announcement, but the ADIZ itself is certainly not an outrageous measure. It merely requires aircraft transiting the zone to submit their flight plans to the Chinese authorities, maintain radio contact and respond promptly to any radio queries.

Under ordinary circumstances, the establishment of such requirements for the air and oceanic approaches to the Chinese mainland would seem to be unobjectionable. But there were two aspects to the new ADIZ that immediately led to controversy. First, the new zone overlapped with existing zones that Japan and the ROK had enforced years ago. Second, part of the zone included the airspace over China's Diaoyu Islands, which Japan occupies and insists on calling the Senkaku Islands.