This post summarizes one of nine case studies included in CSIS’s new report, Countering Coercion in Maritime Asia: The Theory and Practice of Gray Zone Deterrence. The full case study is also available for download here. (Principal case study researcher: Jake Douglas)

In May 2010, senior officials from China and Japan met at a government think tank in Beijing. The Japanese delegation was informed that China was considering establishing its first air defense identification zone (ADIZ) in the East China Sea. Per the U.S. government’s definition, an ADIZ is a designated “area of airspace… within which the ready identification, the location, and the control of aircraft are required in the interest of national security.” People’s Liberation Army officers explained that the new Chinese zone would significantly overlap Japan’s existing ADIZ. It would also include the airspace over the Senkaku Islands, which are administered by Tokyo but claimed by Beijing and Taipei. To address these likely frictions, Beijing recommended that the two countries negotiate rules of behavior for air-to-air encounters in the region. Tokyo feared that acknowledging a Chinese ADIZ could weaken Japan’s position regarding the Senkakus. A few days later, Japan marginally expanded its own ADIZ (originally drawn by its U.S. ally but later enlarged), provoking protests from Taiwan about inadequate consultations.

In May 2013, China’s military submitted a formal proposal for an East China Sea ADIZ. It was approved in August by China’s top party, state, and military organs. A leaked internal document indicated that neighboring states’ perceived push for “marine boundaries disadvantageous to our country” partly motivated the decision. Chinese diplomats had also complained about a U.S.-Japan ADIZ “double standard,” with Tokyo regularly scrambling fighter jets to intercept unarmed Chinese reconnaissance aircraft in international airspace. Some analysts believe that Japan’s 2012 nationalization of the Senkaku Islands drove Chinese leaders to look for ways to save face and punish Tokyo.

In early November 2013, media reports forecast that a Chinese ADIZ announcement was imminent. Beijing notified Seoul “through a diplomatic channel” that the zone would cut into South Korea’s own ADIZ and cover Socotra Rock—a submerged reef occupied by South Korea but subject to a continental shelf dispute among Beijing, Tokyo, and Seoul. South Korean officials expressed “regret” at China’s move but wished to “continue consultations.” Some other “relevant countries” may have been notified beforehand, but the United States received less than an hour of formal notice.

On November 23, 2013, the Chinese ministry of national defense declared the ADIZ’s establishment. A press release marked the zone’s outer boundaries some 200 nautical miles beyond China’s territorial sea, which created overlaps with existing ADIZs from Japan, South Korea, and Taiwan. A ministerial statement outlined “identification rules” applicable to “aircraft flying in the East China Sea Air Defense Identification Zone.” They included reporting flight plans, maintaining radio communications, and keeping transponders turned on. At the end of this list was a vague warning that “China’s armed forces will adopt defensive emergency measures” against uncooperative aircraft.

In official comments on the ADIZ announcement, a Chinese spokesperson explained that efforts to “identify, monitor, control, and dispose of entering aircraft” would help Beijing better “guard against potential air threats.” He argued that the zone’s size reflected the need for sufficient “early warning time” to “ascertain the purpose and attributes” of approaching foreign “combat aircraft” before they reached the mainland.

The U.S. secretaries of defense and state criticized Beijing’s declaration as “unilateral,” “escalatory,” and a “destabilizing attempt to alter the status quo.” The applicability of the U.S.-Japan security treaty to the Senkaku Islands and the United States’ right to freedom of overflight in international airspace were both reaffirmed. In particular, U.S. leaders rejected China’s apparent effort “to apply its ADIZ procedures to foreign aircraft not intending to enter its national airspace” but only operating within or crossing the zone.

Despite its protests, the U.S. government ultimately accommodated China’s identification requirements for civilian aircraft. Yet, military aircraft were another matter. On November 26, two U.S. B-52 bombers flew through the ADIZ in the vicinity of the Senkaku Islands without notifying Chinese aviation authorities. The crew described the flight as “uneventful” with “no contact, no reaction.” Beijing said it “monitored the entire process.”

Japan took a harder line. Japan also scrambled two fighters to intercept an inaugural Chinese ADIZ “air patrol.” Its foreign ministry demanded that China retract the ADIZ. Japanese commercial airlines had already begun reporting flight plans with Chinese authorities, so Tokyo ordered them to cease immediately. Meanwhile the Chinese ambassador in Tokyo suggested the two sides “take measures” to regulate conduct in the overlapping airspace. The Chinese ministry of national defense claimed that it tracked another U.S-Japan assertion of overflight freedoms on November 29. Yet, Tokyo reported that Chinese aircraft did not intercept them.

Seoul was initially more restrained. In a high-level bilateral meeting on November 28, it asked Beijing to redraw its ADIZ to not reach into South Korea’s own ADIZ or include Socotra Rock. South Korean leaders grew disillusioned with their diplomatic approach when the Chinese side refused. The South Korean defense ministry proclaimed that it “cannot accept Beijing’s unilateral declaration” and deployed aircraft into the area without radioing ahead. On December 8, South Korea then announced a major southward expansion of its ADIZ. China, Japan, and the United States were informed prior to the announcement, and Seoul proposed trilateral talks with Beijing and Tokyo “to prevent accidental military clashes.” It also quietly encouraged commercial airlines to follow Chinese regulations.

Beijing has repeatedly argued that its ADIZ follows “common international practices” and was not meant to “change the legal nature of the relevant airspace” or claim a right to shoot down noncompliant aircraft. Indeed, no codified body of international law governs the establishment of or procedures within ADIZs (an invention of the United States in the early Cold War). Formal guidelines in Australia, Canada, Japan, the Philippines, South Korea, Taiwan, and others all require filing flight plans regardless of destination. U.S. ADIZ regulations are similarly ambiguous or inconsistent, even in practice. Like China’s, many longstanding ADIZs cover the airspace above disputed territory and in some cases land effectively controlled by other states.

China’s East China Sea ADIZ has remained a flashpoint since 2013. The crisis led to a palpable hardening of views in Washington on Chinese intentions. At the same time, despite some risky incidents, the Chinese military still conducts most of its air intercepts professionally and safely. Given that there have been persistent rumors about Beijing considering an ADIZ in the South China Sea, it is helpful to draw some lessons from the 2013 ADIZ crisis:

  • First, it would have been difficult, if not impossible, for regional players to prevent China from declaring an ADIZ. Washington, Tokyo, Seoul, and Taipei could ignore the ultimatum, but could not force Beijing to retract it.
  • Second, shaping how Beijing enforced its ADIZ was more feasible. Regional militaries acted quickly to demonstrate that imposing any kind of “no-fly zone” in international airspace would risk a major conflict.
  • Third, the lack of clear international ADIZ rules hinders the ability to deter Beijing from establishing additional zones with rules that its neighbors find concerning.


For more articles in this series, please visit our Countering Coercion in Maritime Asia Report page.

About Michael Green

Michael Jonathan Green is senior vice president for Asia and Japan Chair at CSIS and an associate professor at the Edmund A. Walsh School of Foreign Service at Georgetown University. He served on the staff of the National Security Council (NSC) from 2001 through 2005, first as director for Asian affairs, and then as special assistant to the president for national security affairs and senior director for Asia.

About Kathleen Hicks

Kathleen Hicks is senior vice president, Henry A. Kissinger Chair, and director of the International Security Program at the Center for Strategic and International Studies.

About Zack Cooper

Zack Cooper is a research fellow at the American Enterprise Institute. Previously, he was senior fellow for Asian security at the Center for Strategic and International Studies. He has also served on staff at the National Security Council and in the Office of the Secretary of Defense. He received a B.A. from Stanford University and an M.P.A., M.A., and Ph.D. from Princeton University.

About John Schaus

John Schaus is a fellow in the CSIS International Security Program, where he focuses on defense industry and Asia security challenges. His research areas include Asia-Pacific security issues and U.S. defense policy and industry. Prior to rejoining CSIS in July 2014, he worked in the Office of Asian and Pacific Security Affairs within the Office of the Secretary of Defense.

About Jake Douglas

Jake Douglas was a research assistant with the Japan Chair at the Center for Strategic and International Studies.