China’s announcement on Saturday that it has created an Air Defense Identification Zone in the East China Sea -- including airspace over a small group of islands claimed by both China and Japan -- has prompted serious concerns and sharply worded protests from Washington and Tokyo.  

The Chinese action ratchets up tension in the dispute between China and Japan over sovereignty of the islands known as "Diaoyu" in Chinese and ‘Senkaku’ in Japanese. New rules issued by China require all aircraft flying through the vast Air Defense Identification Zone (ADIZ) to notify China and to obey orders of Chinese officials. The Chinese Ministry of National Defense warned: “China’s armed forces will adopt defensive emergency measures to respond to aircraft that do not cooperate in the identification or refuse to follow the instructions.”  

Although Beijing said that scheduled international airline activity would not be affected by the new rules, a number of airlines -- including two based in Japan -- began immediately notifying China of flights that would go through the newly established zone. The Chinese Ministry of National Defense’s reference to “defense emergency measures” led U.S. Secretary of State John F. Kerry to characterize the Chinese position as a “threat” and to urge China not to implement that threat against aircraft that do not identify themselves nor obey orders from Beijing. He said the United States has urged China to exercise caution and restraint, adding that Washington was consulting with Japan and other affected parties.  

U.S. defense secretary Chuck Hagel also expressed deep concern and characterized the development as a “destabilizing attempt to alter the status quo in the region.” He also made it clear that China’s announcement would “not in any way change how the United States conducts military operations in the region.” In addition to Kerry’s statement that the United States remains “steadfastly committed” to its allies and partners, Hagel added an explicit reaffirmation that the U.S.-Japan Mutual Defense Treaty which obligates America to defend Japan against attack applies to the islands that both Japan and China claim.   

Meanwhile, Japan has lodged a “strong protest” with Beijing, characterizing the Chinese action as “one-sided” and something that “cannot be allowed.”  Not surprisingly, Beijing rejected the protests, denying any intention to generate tensions and, making clear the importance of incorporation of the Diaoyu/Senkakus islands within its ADIZ, and justifying its actions as a move “to uphold its own legitimate rights and safeguard what has always been its own.”  

A Chinese Foreign Ministry spokesman also urged the United States “not to choose sides” over the Diaoyu/Senkaku issue and to “make no more inappropriate remarks.” China’s announcement that it has created the zone was to all appearances technically in accord with international law. The U.S. and several other countries have long established such zones. But as Kerry’s statement on the matter pointed out, the United States “does not apply its ADIZ procedures to foreign aircraft not intending to enter U.S. national airspace” and does not support efforts by any state to do so.  

However, the Aircraft Identification Rules issued by the Chinese Ministry of National Defense apply to all aircraft flying in the ADIZ and make no distinction between those heading for Chinese territorial airspace and others.   In combination with the general peremptory tone of the Chinese announcement and its very broad coverage, its obvious purpose to bring the disputed Diaoyu/Senkaku islands within its purview raises particular concerns. So why did China take this action? In a situation such as the smoldering Diaoyu/Senkaku dispute, there is always the issue of the chicken and the egg -- that is, the question of who took the first step.  

The sovereignty dispute over Diaoyu/Senkaku goes back centuries -- China blames the current problem on Japan's “improper occupation” of the islands in 1895, and then last year breaking an agreement from the 1970s to set the issue aside. (China also blames the U.S. for inappropriately returning administrative control of the islands to Japan in 1972.) Thus, China asserts that it is not responsible for the current imbroglio. However, one presumes that others might see the recent decision by China to send unmanned drones into the area -- to which Japan responded by raising the possibility of shooting them down -- as the more proximate spark. By creating an ADIZ that incorporates the Diaoyu/Senkaku, China presumably feels it has established a parallel basis for challenging and, if necessary, taking action against Japanese aircraft intruding into “Chinese” airspace over the disputed islands. Whether China has any intention of doing so absent other “provocations” is unknowable.  

Moreover, Japan has a rather extensive Air Defense Identification Zone itself that stretches significantly into the East China Sea, and Japanese fighter aircraft frequently scramble in response to “intrusions” by Chinese or Russian aircraft. Beijing’s action could be a precursor to taking similar action against Japanese or perhaps other aircraft intruding into China’s zone.  

The main impact of China’s action would appear -- so far at least -- to be political. But as the various U.S. statements make clear, there is concern that this action will increase tensions and create the risks of an incident through misunderstanding or miscalculation.  

Just as various elements of Chinese sea-based behavior in the immediate vicinity of the Diaoyu/Senkaku seem unlikely to be reversed even if tensions eventually are lowered, the way the Air Defense Identification Zone has been established makes it highly unlikely it will be stood down. The way the rules are generally administered -- especially with regard to any aircraft not heading for Chinese airspace -- could be adjusted. But how they will be applied in the Diaoyu/Senkaku area in the period ahead is a cause of real concern. And that remains to be seen.  

Alan D. Romberg is director of the East Asia program at the Stimson Center, a nonprofit and nonpartisan international security think tank. He earlier spent 27 years with the State Department and 10 with the Council on Foreign Relations.