Introduction1

This report analyzes the establishment of an air defense identification zone (ADIZ) over the East China Sea in November 2013 by the People's Republic of China (PRC, or China), international responses to that action, its consequences, and related matters of national interest and strategy. The report examines the legal, military, and diplomatic aspects of China's ADIZ, with a focus on U.S. interests and issues of concern to Congress. The most salient issues include bilateral relations with the PRC, relations with U.S. partners in East Asia, U.S. military posture in the Asia-Pacific region, and international law (especially regarding freedom of navigation). The 113 th Congress addressed China's ADIZ in resolutions S.Res. 412 and H.Res. 714 , among others. The 114 th Congress may choose, in its oversight of U.S. foreign and defense policy and in its legislative activities, to further shape U.S. responses to China's ADIZ and related policies.
The PRC's East China Sea ADIZ has implications for, and is influenced by, numerous other issues. A partial list of CRS reports on related topics includes:
CRS Report R42930, Maritime Territorial Disputes in East Asia: Issues for Congress , by [author name scrubbed], [author name scrubbed], and [author name scrubbed]
CRS Report R42784, Maritime Territorial and Exclusive Economic Zone (EEZ) Disputes Involving China: Issues for Congress , by [author name scrubbed]
CRS Report R42761, Senkaku (Diaoyu/Diaoyutai) Islands Dispute: U.S. Treaty Obligations , by [author name scrubbed]
CRS Report R41108, U.S.-China Relations: An Overview of Policy Issues , by [author name scrubbed]
CRS Report RL32496, U.S.-China Military Contacts: Issues for Congress , by [author name scrubbed]
CRS Report R41952, U.S.-Taiwan Relationship: Overview of Policy Issues , by [author name scrubbed] and [author name scrubbed]
CRS Report RL33436, Japan-U.S. Relations: Issues for Congress , coordinated by [author name scrubbed]
CRS Report R41481, U.S.-South Korea Relations , coordinated by [author name scrubbed]

	Background and History of ADIZs

An ADIZ is a designated area of airspace over land or water within which a country requires the immediate and positive identification, location, and air traffic control of aircraft in the interest of the country's national security. While many nations have established one or more ADIZs in the interest of national security, no international agreement or consensus exists regarding the establishment of or the flight operations and air traffic procedures related to such airspace. ADIZs are located primarily over waters off coastal nations and often include large swaths of airspace beyond the boundaries of territorial lands and waters.
In 1948, the U.S. Air Force designated several offshore areas as "active defense areas" or "defense zones." From these, the first ADIZs in the world were established in 1950, under an Executive Order directing the Secretary of Commerce to exercise security control over aircraft. Various defense zones were redesignated as ADIZs. The present-day U.S. ADIZs, including the contiguous U.S. ADIZ (over Atlantic, Pacific, and Gulf of Mexico waters, see Figure 1 ), the Alaska ADIZ, the Guam ADIZ, and the Hawaii ADIZ, are codified in Title 14, Part 99, of the Code of Federal Regulations , along with the procedural requirements for flights operating in these designated areas. They are predominantly located over water and typically do not extend to the shore, leaving a narrow strip of sovereign airspace parallel to the coastline that is not within the ADIZ.
U.S. ADIZ procedures apply to aircraft operating to, from, or within the United States through a designated ADIZ. The ADIZ procedures do not apply to U.S. military and law enforcement aircraft. Foreign aircraft, including foreign military aircraft, may generally operate freely within any portion of an American ADIZ not considered part of domestic airspace without complying with the regulatory procedures for communications and positive aircraft identification so long as they do not intend to enter or depart from sovereign U.S. airspace. If however, foreign state or military aircraft are authorized to operate to or from sovereign U.S. airspace, they generally would be required to follow all applicable ADIZ procedures when operating in an ADIZ. 
Procedural regulations mandate that all civil aircraft entering an ADIZ maintained by the United States must be equipped with an operating two-way radio, and in general, unless otherwise authorized by air traffic control, an operating radar beacon transponder with altitude reporting capability. By regulation, flights operating within an ADIZ must file a flight plan and provide required information regarding aircraft and operator identification and planned flight trajectory. Pilots must make position reports to air traffic controllers before entering the ADIZ and upon reaching certain designated reporting points, and must notify controllers of any deviations from the flight plan or from air traffic clearance instructions. Additionally, regulations require that aircraft operating in an ADIZ comply with any special security instructions that the Federal Aviation Administration (FAA) may issue.
The Canadian ADIZ, along with the U.S. ADIZ, is jointly monitored and enforced by the militaries of both nations. Monitoring and enforcement of ADIZ procedures is the responsibility of the North American Aerospace Defense Command (NORAD), a bi-national United States and Canadian organization charged with the missions of aerospace warning and aerospace control for North America. In the United States, FAA handles flight plans and requests, while in Canada NAV CANADA provides air traffic services for aircraft operating within the ADIZ under Canadian civil aviation regulations set forth by Transport Canada. Procedures and regulations are harmonized across both the U.S. and Canadian ADIZ regions.
Among Asian countries, Japan, South Korea, Taiwan, the Philippines, Vietnam, Burma, and India all established ADIZs more than 20 years ago. Japan's ADIZ first came into existence during post-World War II reconstruction to aid Japanese civil air defense initiatives, and Japan codified the zone in 1969. South Korea's ADIZ came into existence in 1951, during the Korean War, to aid military forces in positive identification of non-hostile civil aircraft. See Table 1 for a comparison of ADIZ features among the United States and selected Asian countries.

		Boundaries of International Airspace and Freedoms of the Air

Since ADIZs predominantly lie beyond nations' land borders, their treatment in international law and international policy debates has been a complex and contentious issue. International civil aviation matters are generally encompassed in the Convention on International Civil Aviation, commonly known as the Chicago Convention, which the member nations first agreed to in Chicago, IL, in December 1944 and fully ratified in 1947. While the Chicago Convention does not address or refer to ADIZs specifically, its first two articles define national sovereignty and territorial claims with respect to airspace. Specifically, the Chicago Convention maintains that each nation has complete and exclusive sovereignty with respect to airspace above all recognized territories, including all land areas and all adjacent territorial waters under its sovereignty, suzerainty, protection, or mandate.
The 1982 United Nations Convention on Law of the Sea (UNCLOS) informs present day international policy discussion regarding territorial waters and, consequently, matters of airspace sovereignty beyond land borders. In general, UNCLOS provides that nations maintain exclusive sovereignty within territorial seas, extending 12 nautical miles (roughly 14 statute miles) offshore. Additionally, UNCLOS defines "contiguous zones" as additional outer bands extending to 24 nautical miles (roughly 27.5 statute miles) from shore, in which a nation may exercise certain controls and enforcement actions to protect itself from infringement of its customs, fiscal, immigration, or sanitary laws and regulations. Further, UNCLOS allows nations to establish exclusive economic zones (EEZs), extending as far as 200 nautical miles (roughly 230 statute miles) offshore, in which a nation can exert control over activities impacting economic resources including fishing, mining, oil exploration, and pollution. UNCLOS maintains that all nations may enjoy the freedoms of navigation and overflight within these zones, as well as other internationally lawful uses, which in general may include military exercises, reconnaissance, and other civilian and military use. The United States has not ratified UNCLOS, unlike China, Japan, and South Korea.
Most governments contend that transiting vessels and aircraft maintain high seas freedoms in both contiguous zones and in EEZs, although China and some other nations dispute this interpretation. China, Brazil, and some other coastal nations contend that they have some rights to regulate certain military traffic flying above their EEZs. In contrast, the United States asserts the rights of U.S. military aircraft to transit through ADIZs without complying with procedural regulations established for the ADIZ so long as the aircraft do not intend to enter the nation's sovereign airspace and are not otherwise under the guidance of air traffic control.
China's assertion of control of international airspace overlying its EEZ and U.S. disagreement with this assertion played a part in the April 2001 collision of a People's Liberation Army (PLA, the official name of the Chinese military) J-8 fighter with a U.S. Navy EP-3 reconnaissance aircraft over the South China Sea. The mishap resulted in the death of the PLA pilot and the detention and interrogation of the U.S. Navy crew, which was forced to make an emergency landing on the PRC's Hainan Island. (See CRS Report RL30946, China-U.S. Aircraft Collision Incident of April 2001: Assessments and Policy Implications (pdf), by [author name scrubbed], et al .)
Since the boundaries of various established ADIZs extend even farther than limits established for EEZs, portions of ADIZs clearly lie over international waters and constitute international airspace. For example, portions of the contiguous U.S. ADIZ extend more than 400 miles offshore. Additionally, major portions of established ADIZs extend beyond the limits of territorial seas and are generally not claimed as sovereign airspace except in cases of rare disputes. Consequently, nations generally have no particular international legal basis to establish procedural controls over or requirements regarding the movement of aircraft within such airspace.
In contrast, in airspace above territorial seas, international law does not specifically impart any rights of transit or innocent passage to foreign aircraft. Rather, such overflights are made only upon authorization or agreement of the controlling nation, typically within the context of various bilateral and multilateral aviation agreements, air service agreements, and open skies agreements.
Many coastal nations provide air traffic services beyond their territorial claims and, according to International Civil Aviation Organization (ICAO) standards, may do so in a manner consistent with the procedures established for other airspace under their jurisdictions. In other words, nations are not required to distinguish between sovereign domestic airspace and international airspace for those aircraft to which they provide services, including aircraft transiting through the designated ADIZ. In general, nations harmonize their air traffic procedures and flight rules across all airspace, regardless of whether such services are provided in sovereign airspace or airspace over the high seas. ICAO has designated Flight Information Regions (FIRs) to determine what airport in what country will provide air traffic services in any given location. The entire world is divided into FIRs, so that civilian flights will always have a designated air traffic controller. Many FIRs extend into airspace over the high seas.
ICAO has adopted specific international standards with respect to air traffic rules, but nations may choose to ignore, augment, or modify this general guidance. ICAO provides no specific standard or guidance with respect to the establishment of ADIZs, or air traffic rules or procedures for aircraft operating within designated ADIZs. There are no formal international agreements governing the creation of an ADIZ or procedural controls implemented within any ADIZ. Some legal scholars have questioned the international legal basis for establishing ADIZs and have criticized the practice.
While the Chicago Convention and ICAO are silent with respect to the establishment of ADIZs, the Chicago Convention offers specific guidance with respect to military engagement of civil aircraft, a key component of enforcing procedures established with respect to both sovereign airspace and ADIZs. The Chicago Convention advises that all nations should refrain from the use of weapons against civil aircraft, and in cases involving the interception of civilian aircraft, efforts should be made so as not to endanger the safety of the aircraft and the lives of the persons on board. Notwithstanding such protections, the Chicago Convention expressly acknowledges that a nation is entitled to intercept a civil aircraft overflying its territories without authorization and force it to land if there are reasonable grounds to conclude that the aircraft is operating in violation of established international civil aviation agreements. The Chicago Convention, however, does not explicitly address the interception of civilian aircraft operating outside sovereign airspace.

	PRC's Announcement of an "East China Sea ADIZ"

		PRC's Announcement of and Rules for an ECS ADIZ

On November 23, 2013, the PRC announced that its "East China Sea Air Defense Identification Zone" (ECS ADIZ) would be effective at 10:00 AM that same day. (See the Appendix for the full statement.) The PRC cited its domestic laws as the legal basis. The proclamation included a map of the parameters for the ECS ADIZ, which extends over a large part of the East China Sea, beyond the FIRs managed by Chinese air traffic controllers. The ECS ADIZ asserted coverage of the airspace over the Senkaku Islands, which are administered by Japan and claimed by the PRC as the Diaoyu Islands and by Taiwan as the Diaoyutai Islands. In addition, the PRC's ECS ADIZ asserted coverage of the airspace over a submerged rock over which the Republic of Korea (ROK) asserts administration and on which it built an ocean research station, a rock that the ROK calls Ieodo and the PRC calls Suyan Rock. Moreover, the ECS ADIZ overlaps with the existing ADIZs of Japan, ROK, and Taiwan. Furthermore, the PRC Ministry of National Defense (MND) issued rules for the ECS ADIZ that apply generally to aircraft flying in the ECS ADIZ, regardless of whether the aircraft intends to enter the PRC's airspace. The rules require flight plan identification, radio identification, transponder identification, and logo identification. The rules warn that "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."

		Concerns About the Announcement of the ADIZ and the PLA's Role

Asia security expert Douglas Paal and other analysts have argued that the PRC's announcement of the ECS ADIZ was "clumsy," sudden, and lacked careful consideration of the costs to the PRC's external economic, diplomatic, and military engagements, as well as to its attempts to cultivate an image of a peacefully rising power. Chinese officials and scholars defended China's right to establish an ADIZ, but officials from the United States, Japan, South Korea, and other countries strongly protested the move (see later sections). The announcement came shortly before a high-profile trip to Japan, South Korea, and China by U.S. Vice President Joseph Biden in early December 2013 and just before the planned third meeting of the PLA's Defense Strategic Dialogue with the ROK military. 
The way in which the rules were announced appeared to create uncertainty about their implementation. On the same day as the announcement, the MND spokesman made inconsistent statements. He noted that the ECS ADIZ is beyond the national airspace but also claimed a role for the ECS ADIZ in safeguarding state "sovereignty," as well as territorial land and air security, and aviation order. Although the declared rules were to apply to all aircraft entering the ECS ADIZ, he said that normal flights by foreign airlines in the ECS ADIZ would not be affected. The PLA insisted that the PRC has a right to set up an ADIZ after foreign precedents. The PRC Ministry of Foreign Affairs (MFA) defended the PLA's warning to foreign civilian aircraft and repeated that normal flights of foreign airlines in the ECS ADIZ would not be affected. In January 2014, a PLA Air Force major general, professor, and author acknowledged "misunderstanding" by the Chinese public about whether the PLA Air Force was compelled to direct away or even shoot down aircraft flying in the ECS ADIZ. 

		Assessment of Decision Making by Central Leadership

Although there were indications that the ECS ADIZ regulations were proposed by the PLA and to be implemented by the PLA, the announcement reportedly reflected a top-level decision by Xi Jinping. At the same time that the MND explained the new ADIZ's rules, individuals identified as experts by the PLA presented legal and other justifications in official media, a sign of advance preparation rather than a sudden step. The MND first announced the ECS ADIZ in a high-level "PRC Government Statement." This treatment is consistent with the policy having been the result of a top-level decision. As the authorized administrative organ, the MND then issued its statement and rules for the ECS ADIZ. On November 27, 2013, the PLA Navy's newspaper, People's Navy , published an article by the Director of the Research Office of Maritime Security Policy of the Naval Military Art Studies Institute, saying that the ECS ADIZ is a major decision of the CPC Central Committee, the State Council, and the Central Military Commission (CMC). In another sign that the announcement was not only a PLA decision, PLA spokesmen and MFA spokesmen issued similar statements to reporters to defend the ECS ADIZ. 
Since Xi Jinping completed his formal ascension to the top positions of power in 2012-2013, the PRC has continued an apparent trend of coordinated actions asserting its claims in the East and South China Seas. Xi Jinping reportedly has led a Maritime Security Leading Small Group since early 2012. A top-level report delivered at the November 2012 18 th Party Congress called for China to better exploit maritime resources, safeguard maritime rights and interests, and build China into a maritime power. In April 2013, the PRC issued the 2012 White Paper on the armed forces, entitled "Diversified Employment of China's Armed Forces," that focused more narrowly than in past White Papers on the centrality of maritime disputes in the PRC's perceived security situation and signaled a hardening of its stance to "safeguard" maritime territory and rights with a greater willingness to use force to advance its claims. In July 2013, Xi held a meeting of the Politburo at which he called for building China's "maritime power" comprehensively in political, economic, military, and technological fields. Xi has articulated the PRC's position on its ECS ADIZ to various parties, including Vice President Biden. The announcement was consistent with PRC propaganda's portrayal of Xi as a proactive leader who has "new initiatives." 

	PRC Actions in the ECS ADIZ

PLA actions in the ECS ADIZ have been largely in line with international norms regarding ADIZs, with a few exceptions. Despite initial concerns that the PLA would conduct assertive interceptions of foreign aircraft that did not comply with the identification requirements, there were few incidents in late 2013 and early 2014. In mid-2014, however, PLA Air Force aircraft flew in immediate proximity to Japanese surveillance aircraft on multiple occasions, according to Japanese reports. In October 2014, U.S. Commanders of the Pacific Air Forces and Navy's Seventh Fleet said that the PLA's intercepts in its ECS ADIZ generally have been professional.

		Initial Restraint by PLA in ADIZ Operations

Although the PLA Air Force reportedly has monitored U.S. and Japanese military aircraft that entered the ECS ADIZ, the PLA's enforcement of the ECS ADIZ generally has appeared to be restrained, according to U.S. defense officials. Concerns that the PLA would forcefully administer the zone, as the initial announcement appeared to forewarn, were not borne out in late 2013 and early 2014. For instance, the PLA did not respond to the two U.S. Air Force B-52 bombers that flew on November 25, 2013, from Guam through the PRC's ECS ADIZ without informing Beijing, according to a Pentagon spokesman. Following the PRC's announcement, in late November 2013 Japan and South Korea also flew military aircraft in the PRC's ECS ADIZ without notifying PRC authorities, but both countries indicated that they detected no response from the PLA. The PLA Air Force later said that it patrolled its ECS ADIZ on November 28-29, 2013, and detected U.S and Japanese military aircraft. A Japanese defense official said in January 2014 that the PLA had not taken actions against Japanese military aircraft flying in the zone. The U.S. Pacific Command (PACOM) Commander, Admiral Samuel Locklear, said that there had not been a significant change in U.S. military interactions with the PLA and that the PLA had acted professionally. After its announcement, the PRC assured commercial airlines that normal flights of foreign airlines would not be affected, despite the broad warnings in the ECS ADIZ rules.
There are several possible explanations for the PRC's apparent restraint in enforcing its ADIZ regulations. The PLA may have been surprised by the B-52 flights that occurred within days of the ECS ADIZ announcement and may have felt unprepared to confront the prompt U.S. reaction. The PLA Air Force and PLA Navy might have been inadequately prepared at the operational level to implement the ECS ADIZ. The PLA senior command might not delegate authority to the lower commands for routine operations or for risky ECS ADIZ enforcement that could cause crashes, or centralized control might not be sufficiently effective. The PLA might lack adequate capabilities, including ground-based air surveillance, to monitor fully the whole ECS ADIZ. Still, the Chief of Staff of the Air Force, General Mark Welsh, said in December 2013 that the PLA has the capability and equipment to operate in the zone. An unclassified U.S. Air Force assessment found that China is not likely to maintain a constant presence over the East China Sea with fighters or support aircraft, but the PLA will use ground-based radar coverage to maintain awareness in the ECS ADIZ. The report asserted that the PLA will monitor and manage the ECS ADIZ with shared responsibility among coastal units, command posts in the Nanjing Military Region on the east coast, and centralized commands in Beijing.
Another possible explanation is that the PRC could be pursuing a long-term strategy to alter the status quo in its favor while seeking to avoid a backlash from neighboring countries or the United States. In early 2014, PRC Foreign Minister Wang Yi insisted that Beijing respects Washington's legitimate interests in the Asia-Pacific region and cited Xi Jinping as saying that the Pacific Ocean is large enough for China and the United States. The PRC may be seeking to advance its position over the long term after a short spike in tension, leaving a new status quo with the ECS ADIZ in place. The PRC would acquire strategic advantage by asserting a maximalist position, then seeming to back down, while preserving some incremental gain—akin to a "ratchet" effect. According to this theory, the PRC would project a calm image and justify the ECS ADIZ as a "reasonable" step to which foreign nations should not object. If there is an accident, crisis, or loss of life, Beijing could then blame Tokyo, Seoul, Taipei, or Washington. The ECS ADIZ did not involve aggressive actions by the PLA in the initial phase, but some observers view the declaration of the ADIZ as another of the PRC's incremental law-enforcement and military actions, especially since 2005, to advance its national interests at the expense of other countries.

		China-Japan Incidents in Mid-2014

In May and June 2014, Chinese fighter jets flew extremely close to Japanese propeller-driven reconnaissance airplanes in the overlapping area of the Chinese and Japanese ADIZs on several occasions. The Japanese Minister of Defense called these intercepts "extremely dangerous actions" and said that his government had lodged stern protests with Beijing. The PRC MND disputed that the flybys were dangerous and defended the actions as legitimate enforcement of the ECS ADIZ. The presence of Chinese-Russian military exercises in nearby waters during the May incidents may have increased China's sensitivity to Japanese surveillance activities.
A prior incident with Japan occurred on January 10, 2013, when the PLA reportedly scrambled two J-10 fighters after Japan sent F-15 fighters to observe a PLA Air Force Y-8 early warning aircraft flying over oil and gas fields in the East China Sea.

	PRC Rationales for Creating the ECS ADIZ

One question regarding the PRC's ECS ADIZ announcement is whether it was primarily a politically symbolic statement or instead represented a plan to advance the PRC's administrative control of disputed territory and/or its military anti-access/area-denial (A2/AD) strategy. PRC official media stated that "in fact, prior to the announcement of the air defense identification zone, China already instituted early-warning mechanisms and adopted specific air traffic control measures with regard to the islands over which it claims jurisdiction, including the Diaoyu Islands, and the East China Sea airspace over the related waters." The PLA Air Force has managed air traffic control for the PRC, largely for security reasons, and long before announcing an ECS ADIZ, the PLA scrambled fighters to intercept foreign aircraft, including U.S. reconnaissance aircraft (such as the PRC's April 2001 interception of a U.S. Navy EP-3 plane that resulted in a collision and crisis).
The ECS ADIZ announcement could be primarily a symbolic political statement. An expert on the PLA Navy at the U.S. National War College said that the ECS ADIZ is more a "political declaration than anything that contributes materially to the military capability to carry out" an A2/AD strategy. The PRC leadership could have proclaimed the ECS ADIZ for political reasons to ameliorate internal pressure or struggles inside China. However, PRC leaders agree generally on territorial and maritime claims, especially against Japan. Also, the PRC took assertive or aggressive actions to advance its claims before and after the transition of power from Hu Jintao to Xi Jinping as the top leader in late 2012 to early 2013. There were no nationalistic, violent anti-Japan protests surrounding the ECS ADIZ announcement, unlike the rare protests that erupted during similar periods of heightened tensions with Japan in September 2010 and September 2012. The absence of protests may have been a sign that Chinese leaders did not seek to rally domestic political forces. Comments in China about the ECS ADIZ on the Internet were generally muted.
Over the longer run, Xi could be using the formal ECS ADIZ as a mechanism to push the PLA to higher readiness or alert levels as well as to promote joint operations. Indeed, in asserting that the PLA Air Force scrambled fighters in late November to patrol the ECS ADIZ, the PLA Air Force spokesman specifically stated that both the PLA Air Force and PLA Navy would be on constant alert and jointly safeguard the PRC's ECS ADIZ. Such an effort is consistent with the widely reported exhortations (particularly since 2013) in the defense-related White Paper and in numerous articles that stressed to the PLA that it should promote realistic training to prepare for actual combat and should develop stronger capabilities, including in maritime actions. The "Decision" of the Third Plenum of November 2013 stipulated that, as part of military reform, the PLA should "restructure and rationalize border, sea, and air defense management systems and mechanisms."
One analyst assessed the ECS ADIZ announcement as part of the PRC's international legal assertion of EEZ claims and noted that the eastern edge of the PRC ECS ADIZ closely follows the eastern edge of the PRC's claim to an extended continental shelf in the East China Sea.
The ECS ADIZ could have been intended to elicit an overreaction from Japan, so that the PRC could advance its interests while claiming to be a target of Japanese provocations (see section " Focus on Japan "). Indications are that the PRC's administration of its ECS ADIZ has targeted Japanese aircraft in particular, rather than U.S., South Korean, Taiwanese, or other foreign aircraft. The MND justified extending the PRC's ECS ADIZ to within 130 km of a "certain country," apparently Japan, by pointing to that country's establishment of an ADIZ in 1969 that was 130 km from the coast of the PRC. As of January 2015, the Japanese military has not taken any actions in the contested airspace that have drawn criticism from the international community.
Another motivation for the ECS ADIZ announcement could have been a desire for parity with Japan and other countries that have established ADIZs and have scrambled fighters in response to foreign aircraft. Japan's frequent scrambling of fighters could have increased the PRC's interest in setting up its own ADIZ. The PRC's aircraft, including official, non-PLA planes, have encountered fighters scrambled by the Japanese Air Self-Defense Force (ASDF). Japan's ASDF scrambled fighters 415 times to respond to PRC aircraft from April 2013 to April 2014, an increase by 109 sorties from the previous year. Relatedly, Beijing might have set up the ECS ADIZ for prestige. A Major General in the PLA Air Force asserted that the PRC set up its ECS ADIZ for political-strategic significance as a "great power" because, according to the Major General, an ADIZ is an important symbol of modern countries with air defense capability. Tested by the ECS ADIZ, the PLA Air Force will become stronger, he stressed. In this view, the lack of consultation with other countries is consistent with the PRC's position, as seen in its 2012 Defense White Paper, that it is a major power safeguarding its rights.
Another possible motivation for declaring the ECS ADIZ is the PLA's objection to U.S. Navy and Air Force reconnaissance flights, which PLA officials have identified as an "obstacle" in the military relationship with the United States. A PLA Navy expert noted the ECS ADIZ provides the "legal" authority to track the reconnaissance planes, even though the PLA may not "shoot them down." The U.S. military maintains that its flights operate legitimately in international airspace, not the PRC's airspace.

	U.S. Responses

Promptly after the PRC announced the ECS ADIZ on November 23, 2013, Defense Secretary Hagel called the development a destabilizing attempt to alter the status quo, stated that the announcement would not change U.S. military operations, and reaffirmed that the U.S.-Japan Mutual Defense Treaty applies to the Senkaku Islands. Secretary of State John Kerry expressed concern that the unilateral action was an attempt to change the status quo in the East China Sea and would increase tensions and create risks of an incident. He also stated that the United States does not recognize efforts by any country to apply its ADIZ procedures to foreign aircraft not intending to enter national airspace nor does the United States apply its ADIZ procedures to foreign aircraft not intending to enter U.S. airspace. Secretary Kerry urged the PRC not to implement its "threat" to take action against aircraft that do not identify themselves or obey orders from the PRC. He urged the PRC to exercise restraint. The White House called the PRC's announcement an "escalatory development" that increased tensions.
U.S. concerns focus in part on the way in which the PRC set up its ECS ADIZ. A senior official on the U.S. National Security Council (NSC) staff said that "we [the Obama Administration] saw it as a provocative and escalatory act that increased tensions in the region and reduced the prospect for diplomacy. Regardless of whether China had a right to establish the ADIZ, the way China did it was dangerous." The PRC's ECS ADIZ overlaps with other ADIZs, raising the potential for accidents or incidents that could involve interceptions by fighters. The United States received less than one hour's formal notice before the PRC's ECS ADIZ announcement.
Two days after the PRC's declaration of the ECS ADIZ, the U.S. Navy announced the start of the Annual Exercise (AnnualEx) 2013 involving the carrier strike group led by the USS George Washington in training with Japan's Maritime Self-Defense Force. The U.S. Air Force flew two B-52 bombers from the U.S. territory of Guam on a training flight into the ECS ADIZ without informing China. A Pentagon spokesman said that "we have conducted operations in the area of the Senkakus. We have continued to follow our normal procedures, which include not filing flight plans, not radioing ahead, and not registering our frequencies." Although the bombers' flight reportedly had been planned far in advance, going through with the flight conveyed continuity of operations, sustained support for Japan, and non-compliance with the PRC's ECS ADIZ. In August 2014, a PLA fighter aircraft intercepted at close range a U.S. P-8 surveillance aircraft in international airspace near China's southeastern coast, providing further evidence that the U.S. military continues its normal pattern of operations.

		U.S. Guidance to Commercial Airlines

After the PRC first announced the ECS ADIZ, it distributed its regulations internationally as a Notice to Airmen (NOTAM), which is a notice disseminated by an aviation authority to alert pilots of potential hazards that could affect the safety of their flight. Regarding commercial aviation, the State Department said on November 29, 2013, that the United States generally expects that U.S. carriers operating internationally will follow NOTAMs issued by foreign countries. The State Department also said that "our expectation of operations by U.S. carriers consistent with NOTAMs does not indicate U.S. government acceptance of China's requirements for operating in the newly declared ECS ADIZ." U.S. officials emphasized their concern for the safety of commercial aviation in a potentially volatile situation. To some observers, the messages seemed to be mixed and to undercut the U.S. government's stated refusal to accept the ECS ADIZ. Other observers saw the State Department position as a diplomatic solution that simultaneously upheld the official U.S. protests and the interests of aviation safety. The PRC MFA expressed "appreciation" to the United States for its "constructive attitude" and "cooperation" but accused Japan, whose airlines do not abide by the Chinese requirements in some circumstances, of "maliciously hyping" the matter and urged Japan to "correct its mistakes." PRC media used the U.S. statement to claim "cooperation" in "jointly" ensuring flight safety and to support the legitimacy of the ECS ADIZ. The U.S. statement on NOTAMs appeared amid a tense time and contrasted with the responses of Japan and South Korea, which were advising their commercial airlines not to submit flight plans to the PRC in non-compliance with its ECS ADIZ rules. The ROK later advised its airlines to abide by the PRC's NOTAM.
In a letter to National Security Advisor Susan Rice, Representative J. Randy Forbes summarized concerns about the guidance from the State Department and the FAA that urged U.S. commercial airlines to comply with China's ECS ADIZ procedures, arguing that these seemed to contradict the Administration's own statements. He wrote that "by submitting flight plans to China while traversing international airspace, U.S. airlines will be acknowledging the validity of China's ADIZ at the same time other elements of the U.S. Government are vigorously, and appropriately, contesting Beijing's behavior. Furthermore, at a time when Japan is looking to the United States to be a strong partner, this decision seems to put us at odds with our ally in Tokyo and suggests a lack of policy coordination."

		U.S. Official Statements in Response to the ECS ADIZ

In remarks with Japanese Prime Minister Shinzo Abe on December 3, 2013, in Tokyo, Vice President Biden expressed concern about the increase in tensions and risk of accidents and miscalculation. The next day in Beijing, Vice President Biden told President Xi that the United States does not recognize the ECS ADIZ, looks to China to lower tensions, to avoid enforcement that could lead to crisis, and to establish channels of communication with Japan and other neighbors, according to accompanying officials. He did not call publicly for Beijing to rescind its ECS ADIZ. 
In early December 2013, Defense Secretary Hagel noted efforts towards developing a stronger U.S.-PRC "military-to-military relationship" and called on China, Japan, and South Korea to stay "calm and responsible." At the same briefing, the Chairman of the Joint Chiefs of Staff, General Martin Dempsey, said that "it wasn't the declaration of the ADIZ that actually was destabilizing," but rather the requirement that all aircraft entering the ADIZ report regardless of whether they were intending to enter into the sovereign airspace of China that was destabilizing. 
Four members of the Senate Foreign Relations Committee wrote to the PRC Ambassador in Washington that the unilateral declaration of an ECS ADIZ was "provocative" because it extends over territories "recognized by the United States as under the administrative control of Japan," overlaps with other ADIZs, and has procedures that are potentially dangerous. They stated that the declaration reinforces the perception that China prefers coercion over rule of law and follows a disturbing trend of China's increasingly hostile maritime activities.
After this series of U.S. statements criticizing Chinese behavior, high-level bilateral meetings proceeded as planned. In January 2014, Assistant Secretary of State for East Asian and Pacific Affairs Daniel Russel traveled to Beijing to hold the 5 th round of U.S.-China "Consultations on the Asia-Pacific." The State Department issued a Joint Statement on the talks that stressed "cooperation" and did not mention the ECS ADIZ. The next day in Beijing, Deputy Secretary of State William Burns co-chaired an interim Strategic Security Dialogue (SSD) between diplomatic and defense officials. The State Department said that Burns stressed avoidance of unilateral action by "all sides" to assert territorial and maritime claims and efforts by China to reduce tensions in the East and South China Seas. When asked in a January 2014 hearing of the House Armed Services Committee whether China's actions violate U.S. interests in freedom of navigation, free flow of commerce, or peaceful settlement of disputes consistent with international law, a senior U.S. defense official stated that the ECS ADIZ does not challenge U.S. national security.

	Reaction of Japan

The initial reaction of Japanese leaders to the ECS ADIZ announcement was highly critical. Top officials called on China to rescind its decision to establish the ADIZ, terming it "dangerous" and "one-sided," and Prime Minister Shinzo Abe declared that it would not have any effect on Japan. Japanese military aircraft transited the Chinese ADIZ as part of planned exercises within a week of Beijing's initial announcement. When it was reported that Japanese commercial airlines initially obeyed Chinese requests for identification in the ADIZ, the Japanese government ordered its airlines to effectively ignore Chinese administration of the ADIZ. Japanese commercial aircraft do not file flight plans with Chinese authorities nor respond to requests for identification on routes transiting the ADIZ but not entering Chinese territorial airspace, for example on the route from Tokyo to Taipei.
Since late November 2013, Japan has taken a series of actions designed to thwart Chinese administration of the ADIZ while not further escalating the tense situation. Japan submitted a proposal to the ICAO to examine whether China's actions threatened the order and safety of international aviation. Japan's ADIZ overlaps airspace managed by South Korean air traffic controllers (the Incheon FIR), but the two countries have managed this contradiction for decades without conflict. The Abe Cabinet in mid-December 2013 approved new defense guidelines that emphasize the defense of Japan's southwest islands against incursions from China. The guidelines state, "China is ... showing its attempts to change the status quo by coercion." Japan's parliament, called the Diet, passed a resolution labeling the ECS ADIZ a violation of international law and called for China to withdraw the ECS ADIZ immediately. Foreign Minister Fumio Kishida, in a major speech before the Diet in January 2014, indicated Tokyo's intention to gain international support for the freedom of flight above the high seas.
While the Abe Administration has made enhancing defense capabilities a top priority, Japan has not taken concrete steps to adjust its defense posture or activities to account for the ECS ADIZ. (The Ministry of Defense had already re-deployed 13 E2-C early warning and surveillance aircraft to Okinawa from northern Japan in late 2012.) As in the past, Japanese fighter aircraft continue to scramble and intercept foreign military aircraft that do not identify themselves within the Japanese ADIZ. Reportedly, the United States and Japan agreed to increase their reconnaissance and surveillance activities in the East China Sea, presumably to monitor Chinese practices in the new ADIZ. 

		U.S.-Japan Alliance Relations

The United States and Japan have coordinated at a high level their individual and collective responses to China's ADIZ announcement and have reaffirmed the strength of the U.S.-Japan alliance. American officials expressed appreciation for Japan's restraint in what could be a combustible situation and have joined in criticizing China's actions as destabilizing. At a press conference during his visit to Tokyo in early December 2013, Vice President Biden said, "We, the United States, are deeply concerned by the attempt to unilaterally change the status quo in the East China Sea.... I told the Prime Minister that we will remain steadfast in our alliance commitments." S.Res. 412 , passed by the Senate in July 2014, expresses firm support for Japan and calls on China to refrain from implementing the ECS ADIZ.
In late 2013, however, the two countries took different approaches in some areas, particularly guidance to commercial aviation regarding the Chinese NOTAM (see section " U.S. Guidance to Commercial Airlines "). The decision by the U.S. government to apply normal FAA guidance to the new Chinese NOTAMs contributed to latent anxieties in Tokyo about U.S.-Japan unity and the relative prioritization of China and Japan in U.S. policymaking. Many Japanese strongly praised the training flight of U.S. B-52 bombers through the Chinese ADIZ but were worried when the United States appeared to accede to China on commercial airline guidance. Some American analysts argued that the United States lost credibility by not sufficiently supporting Japan. Any action that the United States takes related to the Senkaku/Diaoyu islands is closely scrutinized in Japan for indications of supporting either Japan or China; signs of ambivalence in Washington cause some Japanese observers to fear abandonment by the United States. However, U.S. officials may be concerned that full-throated denunciation of China may embolden Japan to take actions that would further destabilize the tense situation in the East China Sea.

			The U.S.-Japan Mutual Defense Treaty and the Senkaku/Diaoyu Islands

Some Japanese analysts worry that certain U.S. actions abet China's claim to administer the Senkaku/Diaoyu Islands and thus weaken the U.S. commitment to fulfill its treaty obligations as they relate to the disputed islets. Article 5 of the U.S.-Japan Mutual Defense Treaty states, "Each Party recognizes that an armed attack against either Party in the territories under the administration of Japan would be dangerous to its own peace and safety and declares that it would act to meet the common danger in accordance with its constitutional provisions and processes." Because the United States does not take a position on the sovereignty of the Senkaku/Diaoyu Islands, the fact of Japan's administration is crucial to the U.S. treaty commitment. For more information, see CRS Report R42761, Senkaku (Diaoyu/Diaoyutai) Islands Dispute: U.S. Treaty Obligations , by [author name scrubbed].
For China, it appears that one major reason for creating the ADIZ could have been to bolster its implicit claim to administer the disputed islets (see section " Focus on Japan "). If the United States were to take steps that could be construed as implicit recognition of or acquiescence to some measure of de facto Chinese administration of the Senkaku/Diaoyu Islands, some might argue that it could potentially nullify or at least weaken the U.S. defense obligation. In its own attempt to address this perceived gap, Congress inserted in the FY2013 National Defense Authorization Act ( H.R. 4310 , P.L. 112-239 ) a resolution stating, among other items, that "the unilateral action of a third party will not affect the United States' acknowledgment of the administration of Japan over the Senkaku Islands." Obama Administration officials, including President Obama during an April 2014 visit to Tokyo, have made similar statements. Following the Chinese ADIZ announcement, U.S. officials in the State Department, Defense Department, and NSC have periodically reaffirmed the U.S. defense commitment to Japan and all territories under its administration.
The official U.S. stance that it takes no position on sovereignty in the Japan-China territorial dispute is further complicated by the fact that the U.S. military has used one of the smallest islets of the Senkaku/Diaoyu as a bombing range. The United States has not used the islet for training since 1978, but, according to reports, the U.S. military may be entitled to exercise control over that territory.

	Reaction of South Korea

South Korean leaders initially voiced their strong displeasure with the PRC's ECS ADIZ announcement, but their criticism was not as strident as Japan's. (One news report stated that the ROK government had been informed of China's ADIZ announcement several days in advance.) South Korean Foreign Minister Yun Byung-se said on November 27, 2013, "The issue of the air defense identification zone is making the already difficult regional situations even more difficult to deal with.... We see competition and conflict in the region deepening." In a bilateral meeting of senior defense officials on November 28, South Korea reportedly asked China to redraw its ADIZ so that it did not overlap with the Korean ADIZ, but the Chinese officials rejected this request. On December 8, South Korea announced that it would expand its own ADIZ to include area overlapping with the Japanese and Chinese ADIZs, though conforming to the South Korean FIR. The ROK military expressed its intent to increase patrols in the ADIZ and on December 9 flew a patrol aircraft through the zone without notifying China.
The decision by South Korea to expand its ADIZ to include airspace overlapping with Chinese and Japanese ADIZs showed elements of both consideration and parochialism. On the one hand, the South Korean ADIZ respects the freedom of overflight, including foreign state aircraft. Seoul also consulted with the United States, China, and Japan before making its announcement on December 8, 2013. The calm reactions of Chinese and Japanese officials to the expanded ADIZ likely reflected this consideration. On the other hand, the response in kind to China could appear to legitimize some of Beijing's claims about a need to safeguard national interests through an enlarged ADIZ. South Korea's pursuit of its national interest may have undercut attempts by the United States and Japan to de-escalate the situation based on mutually acceptable principles. Furthermore, the new overlapping area could increase the risk of an incident.
The establishment of the PRC's ECS ADIZ came at a time when South Korea was building closer ties to China and ROK-Japan relations remained mired in acrimonious historical issues regarding Imperial Japan's actions in the early 20 th century. The ECS ADIZ episode appears to have cooled the China-South Korea relationship temporarily by casting a negative light on China's strategy and intentions, although China-ROK relations improved noticeably in 2014. Washington and Seoul are attempting to maintain a strong bilateral relationship while navigating around sensitivities with neighboring countries. One American scholar (and former White House official) argued that the apparent willingness of Seoul to seek a separate accommodation with Beijing, while ignoring the concerns of Tokyo and Washington, was short-sighted and raised questions about South Korea's strategic alignment.
The ADIZ incident also rekindled the long-simmering dispute between China and South Korea over a submerged rock in the Yellow Sea. The undersea feature, called Socotra Rock by the United States, Ieodo by South Korea, and Suyan Rock by China, is located in the area of the sea claimed by both China and South Korea as within their EEZs. Since 2003, South Korea has maintained an ocean research station built on a raised platform above the submerged rock. The new Chinese ADIZ includes airspace over Socotra Rock, which had previously been within the Japanese but not the Korean ADIZ, although it is now included within the expanded Korean ADIZ.

	Reaction of Taiwan

On November 23, 2013, the Taiwan government declared that (1) Taiwan has sovereignty over the Diaoyutai (Senkaku) Islands with no change due to the PRC's ECS ADIZ and that Taiwan will continue to defend that sovereignty over the islands and continue operations to protect fishermen; (2) each side should use peaceful dialogue to resolve disputes in line with President Ma Ying-jeou's "East China Sea Peace Initiative" of August 2012; (3) Taiwan's military will use peaceful principles of Ma's initiative and adopt appropriate measures in light of the overlap between the PRC and Taiwan ADIZs; and (4) Taiwan is "gravely concerned" and will maintain close contact with all sides to maintain peace and stability. In contrast to Japan, Taiwan instructed its commercial airlines to submit flight plans to the PRC's authorities, arguing that the general directive is in accordance with international regulations rather than in recognition of the PRC's ECS ADIZ. The Democratic Progressive Party (DPP), an opposition party more wary of the PRC than the ruling Nationalist Party (also known as the Kuomintang), urged a stronger protest. Taiwan's legislators from both parties issued a joint statement from the Legislative Yuan urging the Ma Administration to lodge a strong protest, commercial airlines not to submit flight plans to the PRC, and the PRC to rescind its ECS ADIZ. In 2010, Taiwan protested strongly to Japan when it expanded slightly its ADIZ to fully cover the airspace over Japan's Yonaguni Island, though there is no dispute over the island. Taiwan opposed the change to Japan's ADIZ line, and Taiwan's Foreign Minister raised a question about whether Japan's redrawn ADIZ would "threaten" Taiwan's airspace. 
After the lawmakers' joint statement, Taiwan's Executive Yuan, or Cabinet, added that the military would not change its operations as a result of the PRC's ECS ADIZ announcement and would conduct patrols and reconnaissance operations in Taiwan's ADIZ. Although Taiwan demarcates its ADIZ as extending west of the Taiwan Strait to cover part of the mainland, Taiwan's Air Force and the PLA Air Force have a tacit understanding that their fighters should not cross the median line in the Taiwan Strait (Taiwan does not attempt to administer the portion of the ADIZ over mainland China). Taiwan's Air Force patrols and training continued unchanged, including up to 30 patrols in the overlap between their ADIZs in the week after the PRC's announcement. Taiwan has protested and scrambled fighters in response to the flights of the PLA's aircraft through Taiwan's ADIZ, including aircraft not flying toward Taiwan. For example, Taiwan's military announced that on August 25, 2014, a PLA Y-8 surveillance aircraft flew four times through the southwestern corner of Taiwan's ADIZ. Taiwan's Air Force scrambled fighters to intercept the Y-8 aircraft and "escort" it out of the ADIZ, though the PRC planes did not fly toward Taiwan.

	Implications for U.S. Policy

The PRC's ECS ADIZ has implications for U.S. policy in terms of the potential for conflict, escalation of tension, Sino-Japanese tensions, a strategic challenge to the United States, and U.S.-China military-to-military exchanges.

		Potential for Conflict

By creating an overlapping area where different militaries seek to administer airspace, China's ECS ADIZ may increase the risk of an incident that could lead to a military conflict. A confrontation between military aircraft at close proximity could provoke the use of force and then retaliation, especially in the absence of mutual trust. Depending on the effectiveness of de-escalation measures and the intent of the parties involved, a small-scale clash could escalate to a more significant conflict between large, modern militaries. In early 2013, PLA Major General Zhang Zhaozhong said that Beijing needs to "break" Tokyo's ADIZ, saying, "If their fighters come and our fighters don't go out, from a diplomatic and military perspective, there is no reciprocity: It's not good. But if both sides bring out fighter jets, as to whether that might lead to a clash between them, that is another question." 
The incidents in May and June 2014 between Chinese and Japanese aircraft (see section " China-Japan Incidents in Mid-2014 ") illustrate the potential for a spark to ignite a larger, combustible situation. The potential for an accidental clash in the air provided a reminder of the aircraft collision crisis of 2001, when a PLA Navy F-8 fighter hit a U.S. Navy EP-3 reconnaissance plane flying over the South China Sea. The crisis took place in spite of U.S. protests to the PRC months before the crisis that PLA pilots engaged in a pattern of increasingly unsafe behavior.
The presence of unmanned aerial vehicles (UAVs) in the airspace over the disputed islets could also spark conflict. On September 9, 2013, the PLA apparently flew a UAV within 125 miles of the Senkaku Islands, without entering Japan's territorial airspace. Japan scrambled fighters in response to the unidentified UAV that Japan said intruded into its ADIZ. Later, in October, Japan reportedly prepared an option to shoot down foreign UAVs that do not respond to warnings to leave Japanese territorial airspace. The PRC Defense Ministry said then that the PLA's UAVs are used in normal training and activities and that Japan's shooting down of aircraft would be an act of war.
The PRC official media's justifications for the ECS ADIZ included arguments about China's right to "self-defense" and to safeguard "sovereignty," but not signals of deterrence to prevent a crisis or war. In the past, the PRC has warned of the use of force or retaliation to compel an adversary to back down from an impending crisis or conflict. For example, in threats against Taiwan in December 1992 and March 1993, CPC General Secretary Jiang Zemin and Premier Li Peng warned of necessary "resolute" or "drastic" measures to prevent Taiwan's independence. Past PRC warnings have included phrases such as "we will not attack if we are not attacked; but if we are attacked, we will certainly counter-attack." Considering this pattern, the PRC's ECS ADIZ does not appear intended to provoke a conflict with Japan, South Korea, Taiwan, or the United States. The action is consistent with an assessment in 2013 by several experts that found that the most likely challenge to the U.S.-Japan alliance over the next 15 to 20 years is not a full-scale military conflict between China and Japan or the United States but the more likely attempts by China to use coercively its growing military capabilities to influence or resolve disputes with Japan in China's favor without resorting to an attack.

		Escalation of Tension

To U.S. Naval War College scholar Andrew Erickson and other experts on the PLA, the creation of the ECS ADIZ fits a pattern of numerous actions by China that intentionally raise the risks of accidental clashes and exacerbate tensions to seek concessions from other countries or acceptance of a new status quo. These actions also put pressure on the U.S.-Japan alliance. Erickson and others assert that Beijing perceives that it can control the escalation of tension while shaping foreign security perceptions and seeking compromises. A chief justice in the court system of the PLA Navy stated that the ECS ADIZ "will not only not bring about an intensification of the situation in the East China Sea, it will actually control the escalation of the complex situation in the East China Sea and be an effective measure for protecting the peace and stability of the East China Sea." This quote illustrates the point that, in the eyes of many Chinese strategists, some actions that escalate tensions may not be inherently dangerous or undesirable, and thus other countries should not be outraged by these tactics.
Since September 2012, the PRC's actions have shown a trend toward greater use of military assets to assert administrative control in the East China Sea, on top of the previously high-profile use of official maritime law enforcement ships. The PRC's militarized actions have escalated from regular patrols by official maritime law enforcement ships (including into the territorial waters of the Senkaku/Diaoyu Islands to claim them as the PRC's territorial waters), patrols by PLA Navy ships, patrols by official aircraft, announced scrambling of fighters to match Japan's scrambling of fighters, to PLA Navy actions beyond patrols, and establishment of the ECS ADIZ for PLA air control. Beijing has justified these other actions by its need to defend China from increasing external threats.
The PRC's designation of the ECS ADIZ further raised the prospects that East China Sea tensions could escalate into a crisis involving Japan, a U.S. ally, and that the United States could be drawn into a conflict with the PRC. It is unclear whether the PRC was interested in raising tension, perhaps to provoke Japan, to undercut U.S. alliances by trying to undermine trust in U.S. commitment or capability, or to hint of U.S.-China co-management of what Beijing calls "third parties" such as U.S. allies and partners. The concept of a "G-2," or Group of Two, between the United States and China continues to worry some countries wary of China.
In late 2013, the PRC blamed Japan alone for "provocations" and the lack of dialogue to manage or reduce tension. In March 2014, the PRC MFA did not agree to a Japanese proposal for a maritime liaison mechanism to avoid escalation of tension, saying instead that the problem remained with what the PRC called Japan's unilateral provocations. China eventually agreed in September to resume talks with Japan on the communication mechanism, which would establish a hotline between defense officials and determine radio frequencies to be used for communications between ships and aircraft of the two nations. The face-to-face meeting of Prime Minister Abe and President Xi in November 2014 may provide momentum to those talks.

		Focus on Japan

The designation of the ECS ADIZ appeared to focus on the PRC's goals vis-à-vis Japan in particular, although PRC officials cited broad foreign precedents for ADIZs and stated that the ECS ADIZ is not aimed at any country. Chinese commentators drew attention to Japan's ADIZ before and after the PRC's formal announcement of its ECS ADIZ. The PLA's newspaper published an article that criticized Japan for its concerns about the ECS ADIZ and for the Japanese government's purchase of three of the disputed islets, saying that the PRC's demarcation of the ECS ADIZ "of course had to include the Diaoyu Islands." Official PRC media published an article arguing that the ECS ADIZ announcement has started the struggle with Japan over air control over the East China Sea. After the ECS ADIZ announcement, commentary in the official PRC media harshly criticized only Japan for its reaction, while expressing "appreciation" to the United States for its "neutral stance" on the China-Japan territorial dispute. Although other neighbors protested, Chinese media have avoided criticisms of Seoul or Taipei.
In one view, the PRC's objective might be primarily directed at rival claims with Japan over the Senkaku/Diaoyu/Diaoyutai Islands. The ECS ADIZ might be a means to press Japan to recognize the existence of a dispute and enter into negotiations. A retired PLA general, Xu Guangyu, said that "the eventual purpose [of the ECS ADIZ] is to force Japan to sit down with China, to avoid miscalculation and escalation." The PRC could claim its own or joint management to undermine Japan's exclusive administration of the islands, which some might argue could undercut the applicability of the U.S.-Japan defense treaty (see section " The U.S.-Japan Mutual Defense Treaty and the Senkaku/Diaoyu Isl "). The ECS ADIZ could be viewed as one action among many that the PRC has taken to try to change the status quo at the expense of rival claimants in the East and South China Sea.
China announced the ECS ADIZ against the backdrop of numerous official statements that go beyond the two countries' territorial dispute and that appear intended to discredit Japan more broadly. The ECS ADIZ announcement came shortly before the PRC's high-profile commemoration of the 70 th anniversary of the Cairo Declaration, an event at which the PRC not only reiterated its claim to sovereignty over the disputed islands but also continued a campaign of criticizing Japan's historical aggression in World War II as well as Japan's behavior today. If the PRC's challenge to Japan indeed extends beyond a disagreement over disputed islands, then concessions by Japan would not necessarily reduce the risk of conflict and could encourage additional coercive actions by the PRC. China could be engaging in zero-sum competition with Japan that entails broad economic, military, and political rivalry on the world stage—a rivalry in which the Senkaku-Diaoyu Islands dispute is only one element. Another perspective is that the appearance of China-Japan competition is the product of China's emergence as a major power.

		Strategic Challenge to U.S. Leadership and Alliances

There is debate in the academic and policy communities over whether the PRC accepts the current international order or is seeking to re-define it. The creation of the ECS ADIZ suggests to some observers that the PRC is asserting its own rules rather than accepting established rules and practice. Beijing has rebutted the charges that it is upending the international order and has argued that other countries have indicated their agreement with the ECS ADIZ by complying with PRC regulations. The PRC MND claimed that, in the first month after announcing the ECS ADIZ, the PLA "controlled" almost 800 flights of foreign military aircraft that entered the ECS ADIZ, and 56 airlines from 23 "countries and regions" notified PRC civil aviation authorities of their flight plans for 21,475 flights. At the same time, Beijing also has questioned one feature of the international order: U.S. military alliances. Right after the ECS ADIZ announcement, Vice Foreign Minister Liu Zhenmin said that "in Asia, military alliances are still an objective existence. Some external powers and regional members show their support. But for China, it is already an outdated concept in international relations, and does not fit with the new type of state-to-state relations."
A related question is whether the PRC is reacting to the actions of other countries or is taking proactive steps to incrementally advance its maritime claims and project power at the expense of other countries. The Director of National Intelligence (DNI) James Clapper testified to Congress in January 2014 that "China will probably continue its increasingly proactive approach to maritime disputes, including a hardline stance toward Japan over the Senkaku Islands." DNI Clapper also stated that the PRC has endeavored indirectly to counterbalance U.S. influence and to sow doubts about the sustainability of the U.S. strategic rebalance to Asia and U.S. willingness to support its allies and partners.
Some analysts assess that the PRC's ECS ADIZ is changing international rules and testing (if not costing) the United States its international influence. Michael Green, a former Senior Director for Asia at the NSC during the George W. Bush Administration, asks whether the Obama Administration sees the ECS ADIZ as "a Japan-China problem that needs to be managed or as part of a longer-term test of wills with Beijing." Green also argues that the ECS ADIZ announcement was not "just an ill-conceived slap by Beijing against a testy Japan. The reality is that the new ECS ADIZ is part of a longer-term attempt by Beijing to chip away at the regional status quo and assert greater control over the East and South China Seas." He urged the Administration to consider China's actions as the use of coercion to change the status quo.
Another commentator saw a strategic challenge:
Over the past five to 10 years, China's "peaceful rise" has given way to more assertive efforts to challenge the regional status quo. There has been no formal declaration of a Chinese "Monroe Doctrine," no announcement of a Beijing-centered "Asian Co-Prosperity Sphere," and certainly no fiery speeches denouncing the existing order the way that Hitler used to rail against Versailles. Instead, what we've seen is a more gradual, low-intensity effort to challenge current arrangements and to pressure other states to accept revisions that are more to Beijing's liking. Sometimes, the object of attention is a reef or some small islands; sometimes it is a declaration of sovereignty over contested waters; and most recently, it was the unilateral announcement of an "air defense identification zone." In each case, the goal has been to reinforce Chinese claims to particular territorial arrangements, but also to establish China's position as the power in the region whose demands must be respected.
Former Assistant Secretary of State for East Asian and Pacific Affairs Kurt Campbell observed that the PRC's military warning to civilian airliners "creates unwelcome comparisons between the former Soviet Union with today's China.... It suggests a nation more interested in the pursuit of 19 th century-like spheres of influence and prohibited areas, rather than a 21 st -century nation committed to sustaining an open and transparent regional operating system."
A China specialist at the Naval War College, Peter Dutton, assessed that the PRC is challenging the U.S.-led, open maritime system and is using force and legal assertions: a "power and law approach." He argued that the ECS ADIZ is consistent with a strategy to use legal language to increase incrementally China's jurisdictional control over the "near seas." Dutton argued that the ECS ADIZ has a legal implication regarding accession of the United States to UNCLOS and leadership of international rules. Another China expert, Bonnie Glaser, testified that the PRC's use of coercion, bullying, and "salami-slicing" tactics, including the ECS ADIZ, has implications for U.S.-PRC strategic competition for power.
In another view, the issue is the extent of the strategic challenge. Observers holding this view believe that China's challenge could be limited to Asia, or what the PRC calls its "periphery." In this view, Beijing is not broadly overturning the international order but subtly and selectively challenging access to the global commons. A professor at Naval War College wrote that the PRC's strategy is not access denial but "selective access denial." He noted that "should Beijing try to bar foreign access to Asian seas and skies entirely, it would simplify the problem for Washington. No U.S. president could tolerate blanket access denial.... Instead, though, China is daring America to mount a massive effort to defend things of seemingly trivial importance."

		Military-to-Military Exchanges

The PRC's formal announcement of the ECS ADIZ showed continued limitations in U.S. military contacts with the PLA. The PLA did not present a particular plan or detailed discussion of a new ADIZ during a meeting in August 2013 in Honolulu of the bilateral Military Maritime Consultative Agreement (MMCA) between PACOM and the PLA Navy. The PLA Air Force did not attend the MMCA meeting. The ECS ADIZ announcement appeared right after the Vice Chief of Naval Operations (CNO), Admiral Mark Ferguson, visited the PRC on November 10-14, 2013. He met with PLA Navy officials who included Commander Wu Shengli and Vice Admiral Su Zhiqian, the East Sea Fleet's Commander, but was not informed of the PRC's plan to establish an ADIZ. Defense Secretary Hagel acknowledged in a joint press conference with Chairman of the Joint Chiefs of Staff Martin Dempsey on December 4, 2013, that he had "not spoken to my Chinese counterpart" about the ADIZ; General Dempsey indicated that he had "actually reached out to the schedulers to connect me with my Chinese counterpart," but that contact had not yet been made. Hagel noted efforts towards developing a "stronger military-to-military" relationship with the PLA. Some officials and observers opined that military-to-military management of tensions can reduce the risks to stability from the increasingly competitive aspects of the PRC's approach to the United States and U.S. allies. For more information, see CRS Report RL32496, U.S.-China Military Contacts: Issues for Congress , by [author name scrubbed].

	Potential Further PRC Actions

The PRC has a wide array of options related to the ECS ADIZ. Actions likely to be seen as constructive by other countries include restrained enforcement of the ECS ADIZ rules; prevention of nationalist activists from landing on the disputed islands; and consultations with other countries and the ICAO to conform its ECS ADIZ to international rules and practice. However, in an indication that the ECS ADIZ poses a challenge beyond the island dispute with Japan, Beijing stated that it was considering other ADIZs. On the day of the ECS ADIZ announcement, the MND stated that the PRC will establish other ADIZs "at the right moment after necessary preparations are completed." The MND spokesperson reiterated that position at a news conference on November 28, 2013.
As possible future steps, China could announce an ADIZ for the South China Sea, an ADIZ for the Tonkin Gulf, and/or an ADIZ for the Yellow Sea. Although the MND spokesman assured that the ECS ADIZ is beyond national airspace and not a "no-fly zone," the PLA in the past has tried to assert that it may deny access to the Yellow Sea for foreign military exercises or transit. The PRC also could declare an ADIZ for the Taiwan Strait or extend the ECS ADIZ toward Taiwan. These possible future steps raise questions about the need for international talks with Beijing and about U.S. strategy for discouraging China from announcing new, problematic ADIZs (see section " Oppose Other PRC ADIZs " for U.S. official statements) and for responding to potential new ADIZs.
In the near term, the PRC would face significant challenges in implementing an ADIZ over the South China Sea. The PLA may need to build up its radar and other capabilities to support another ADIZ, especially to cover the southern part of the South China Sea, which is a great distance from PLA bases. The PLA Air Force has limited ability to project power farther from PRC territory, including over the South China Sea, although these limitations will depend on the PLA's aerial refueling capability. The PRC occupies the Paracel Islands as well as seven reefs, but no islands, in the Spratly Islands. However, since 2013 Chinese ships have been dredging the seabed around several reefs to construct artificial islands that could support airfields, a development that may alleviate the PLA's need for in-flight refueling to maintain air control of the South China Sea. Official PRC media indicated that an aircraft carrier could help with the problem of limited endurance of fighters flying patrols over the South China Sea, especially out to the southern edge of China's claimed jurisdiction. In December 2013, the PLA Navy's first aircraft carrier, the Liaoning , sailed to the South China Sea for testing and training. At a congressional hearing in February 2014, the Director of the Defense Intelligence Agency Lieutenant General Michael Flynn testified that China's first aircraft carrier, commissioned in late 2012, will not reach its full potential until it acquires an operational fixed‐wing air regiment over the next several years.
Announcing an ADIZ for the South China Sea could create political problems for the PRC. Such a move could exacerbate tense ties with some countries and could spur a more coordinated approach at the 10-nation Association of Southeast Asian Nations (ASEAN), which, in turn, could compel Beijing to deal multilaterally with several Southeast Asian countries instead of Beijing's preferred use of leverage in bilateral contacts. Indeed, PRC media indicated that a "South China Sea ADIZ" would present complicated problems for the PRC's external engagement with Southeast Asian countries, drive a wedge between China and ASEAN, and raise concern about a "China threat." In early 2014, the PRC MFA denied that China was preparing to announce a "South China Sea ADIZ" by saying that China does not feel a threat from Southeast Asian countries and that reports of such an ADIZ were rumors created by Japan. In November 2014, a PRC MND spokesperson addressed the possibility of a South China Sea ADIZ, "We have said on many occasions that whether or not to set up an [ADIZ] depends upon various factors, for example, the air threat that the country faces and the overall security environment. And we have confidence as to our relationship with the countries surrounding the South China Sea and we also have confidence in the overall stability of the situation in the area."
Following the establishment of the ECS ADIZ, China could challenge operationally Japan's administrative control of the Senkaku/Diaoyu islands. For example, the PLA could fly aircraft, including helicopters or fixed-wing aircraft, into the airspace over disputed islands or reefs, or PLA aircraft could intercept foreign aircraft. Official PRC agencies or the PLA could land UAVs on a disputed island. China Coast Guard or PLA Navy ships could enter the territorial waters of the Senkaku Islands for longer periods of time. The PRC could then portray the reactions of Japan (and/or other countries) as "provocations" and exploit them to advance the PRC's control.

		Costs and Consequences for the PRC

The PRC's management of the ECS ADIZ and its decision whether or not to establish other ADIZs will be based on Beijing's perception of costs and benefits. Some observers assess that the PRC incurred costs by, in one stroke, tainting the international image of its "peaceful rise" and undercutting multiple engagements with Japan, South Korea, Taiwan, Australia, the United States, and other countries. Defense Secretary Hagel and Singapore's Minister of Defense Ng Eng Hen met on December 12, 2013, and they discussed China's "troubling" ECS ADIZ announcement and the concerns of Southeast Asian nations. Days later, the leaders of Japan and ASEAN held a summit in Tokyo. They agreed to enhance cooperation in ensuring the freedom of overflight and civil aviation safety in accordance with universally recognized principles of international law, including the 1982 UNCLOS, and standards of the ICAO, without explicitly pointing to the PRC's ECS ADIZ announcement. PRC official media, nonetheless, insisted that Southeast Asian leaders had shown prudence and a commendable unwillingness to take a clear position on whether to align with Japan to counter China on the issue of freedom of navigation.
Some commentaries called for a strong, sustained U.S. stance to oppose China's ECS ADIZ, to forestall future challenges, as well as to bolster U.S. leadership in a coordinated approach among allies and partners. The Washington Post called for opposition, arguing that "if this air zone is allowed to stand, it may encourage China to step up the pressure in other ways, too." The New York Times contended that "given China's unilateral decision, with its threat of possible military action, the United States needed to stand up for its ally Japan, for the principle of freedom of navigation of the seas and skies, and for other Asian nations that also have territorial disputes with China in the East China Sea and the South China Sea."
Observers noted that the PRC's ECS ADIZ declaration raises a question of whether and how to impose costs, including cancellations of symbolic visits. Some officials say that dialogue is critical in times of tension and that it is more important to reduce the rising risks in the relationship with Beijing. Other analysts worry about the possibility of sending unwanted signals to Beijing if the United States or other countries accept the PRC's provocations without penalty. Beijing could use tensions to drive wedges between the United States and allies, while seeking to strengthen ties with Washington and isolate its allies.

	Policy Options and Congressional Oversight

Possible congressional actions or oversight of policy include legislation, hearings, and other options that could focus on addressing the PRC's ECS ADIZ, U.S. military contacts with the PLA, strategic reviews of policy, crisis-management and confidence-building measures, international institutions and rules, alliances with Japan and South Korea, and standards and procedures at the ICAO.

		Proactive U.S. Policy

Alongside debates about whether Beijing's declaration of the ECS ADIZ merits imposing costs of some kind, the issue also raised questions about the need for a more forward-looking, rather than reactive, U.S. policy toward China. Such a policy might encourage China to pursue non-militarized measures and avoid intercepts by military ships or aircraft in order to reduce the risks of accidents and escalation. In early December, Vice President Biden told President Xi that the United States looks to China to lower tensions, to avoid ADIZ enforcement that could lead to a crisis, and to establish channels of communication with Japan and other countries to avoid the risk of mistake, miscalculation, accident, or escalation. In early 2014, Assistant Secretary of State Russel stated, "In the short term, there is a crying need for a practical mechanism to prevent crises or manage them should they occur. The critical thing in the short term is that no incident be allowed to trigger an escalatory cycle, and the environment and structures be put in place that minimize the risk of an incident taking place at all."
At a U.S.-PRC summit in Beijing in November 2014, Presidents Obama and Xi announced two memoranda of understanding (MOUs) as military-to-military confidence-building measures: an MOU on the Notification of Major Military Activities and an MOU on the Rules of Behavior for Safety of Air and Maritime Encounters (expanded to cover coast guards as well militaries). The MOU on Rules of Behavior commits both sides to follow established international laws and rules, rather than concluding new, binding, bilateral rules or agreements. The two sides issued an annex on surface-to-surface encounters between ships. Reflecting the greater difficultly in dealing with air-to-air encounters and with the international laws that govern military aircraft, the two sides did not complete an annex on air-to-air encounters, but agreed to complete negotiations on that annex in 2015. The U.S.-PRC announcement shows a mutual interest in avoiding unplanned, dangerous encounters at sea and in the air. The MOU demonstrates a potential outcome of discussions with PLA operational officers and top leaders about aviation safety and security, military exchanges, and maritime law enforcement. However, some analysts contend that the MOU does not address fundamental differences in the interpretation of international law between the United States and China, and that many past encounters between ships and aircraft were not "unplanned" but rather intentionally provocative. Further dialogues, including those at international legal or other forums, may be necessary to test whether Beijing is asserting its claims based on international law or rules (such as international aviation practices in setting up ADIZs), or on another basis.
Some analysts argue that quiet diplomacy might be more effective than public, high-profile defiance that would goad China into a counter-productive hardening of its approach in announcing the ECS ADIZ. The United States, however, was already pursuing a quiet diplomatic approach prior to the announcement of the ECS ADIZ. For example, Washington and Tokyo did not emphasize publicly the alliance's coverage of the Senkaku Islands in a high-level joint statement in October 2013, demonstrating, perhaps, awareness of Beijing's sensitivity to public emphasis on the Senkaku/Diaoyu issue in U.S.-Japan joint statements. Days before the announcement, National Security Advisor Susan Rice gave a speech in which she cited U.S. concerns about the rise of maritime disputes in Asia, a growing threat to U.S. interests in peace and security, but she did not reiterate that the U.S.-Japan defense treaty covers the Senkaku Islands.

		Addressing the ECS ADIZ

			Clarify Official U.S. Position on the ECS ADIZ

Congress could call for the Obama Administration to formulate a coherent, consistent, and coordinated message about China's ECS ADIZ, including clarification of (1) whether U.S. airlines should file flight plans when entering the ECS ADIZ, and (2) the meaning of not accepting officially the ECS ADIZ. S.Res. 412 states that the Senate "urges the Government of the [PRC] to refrain from implementing the [ECS ADIZ], which is contrary to freedom of overflight in international airspace ... " The resolution reaffirms the strong support of the U.S. Government for freedom of navigation and other internationally lawful uses of sea and airspace in the Asia-Pacific region and states that it is U.S. policy, inter alia, to assure the continuity of U.S. operations in that region. On December 3, 2014, the House of Representatives (113 th Congress) passed H.Res. 714 , which states that the House does not recognize the PRC's declared ECS ADIZ, describes it as "contrary to freedom of overflight in international airspace," and calls on China to "refrain from taking similar provocative actions elsewhere in the Asia-Pacific region, including in the South China Sea."

			Lead International Actions

Congress could urge the Obama Administration to lead a coordinated response with Japan, South Korea, and perhaps Taiwan, and to prevent any attempts by China to use a "divide and conquer" strategy to induce at least one party to cut a side deal (whereby Beijing ameliorates one party's particular grievance). Congress could call for the United States and its allies to continue or increase combined military exercises in the region, including in the Yellow Sea and South China Sea. Congress also could call on the Administration to lead efforts or support an ally's proposal for multilateral talks about the PRC's ECS ADIZ or crisis management mechanisms. The United States might urge China to consult with other countries in advance of announcing any future ADIZs in a way that would be in conformity with international norms.

			Oppose Other PRC ADIZs

Congress could call on the Administration and other countries to oppose other ADIZs that the PRC might seek to establish. S.Res. 412 and H.Res. 714 urge China to refrain from taking further provocative actions similar to the ECS ADIZ announcement. After the PRC's designation of the ECS ADIZ, it appears that the Obama Administration began to take a more proactive position pertaining to maritime disputes not only in the East China Sea but also the South China Sea. In mid-December 2013, Secretary of State Kerry visited Hanoi and Manila, where he expressed concerns about the ECS ADIZ announcement and declared that China should refrain from taking similar unilateral actions elsewhere, particularly over the South China Sea. The State Department's spokesperson also said that the United States would consider an ADIZ over the South China Sea as a provocative and unilateral act that would raise tension.
In February 2014, Assistant Secretary of State for East Asian and Pacific Affairs Daniel Russel articulated a stronger Administration position in his testimony at a hearing of the House Foreign Affairs Committee Subcommittee on Asia and the Pacific:
China's announcement of an Air Defense Identification Zone (ADIZ) over the East China Sea in November was a provocative act and a serious step in the wrong direction. The Senkakus are under the administration of Japan and unilateral attempts to change the status quo raise tensions and do nothing under international law to strengthen territorial claims. The United States neither recognizes nor accepts China's declared East China Sea ADIZ and has no intention of changing how we conduct operations in the region. China should not attempt to implement the ADIZ and should refrain from taking similar actions elsewhere in the region.
The Commander of the U.S. Pacific Air Forces said in early 2014 that any attempt by the PRC to set up an ADIZ over the South China Sea would be very provocative and that the United States strongly conveyed its opposition to such a move to the PRC. A senior NSC official asserted that the United States would change its military deployments and force posture in the region if the PRC set up another ADIZ. The NSC official did not provide specifics, but such a shift might entail the deployment (rotational or permanent) of more U.S. military aircraft and other surveillance and reconnaissance assets to Northeast Asia or Southeast Asia.

			Operations to Assert Freedom of Navigation and Overflight

Congress could consider whether the Obama Administration's articulation of heightened concern about China's challenges to access in international airspace and waters warrants follow-up options to buttress the U.S. statements. Although U.S. military leaders have said that U.S. military flights have continued without change after the PRC's ECS ADIZ announcement, they have not been as publicized as the B-52 flights days after that announcement. Potential options for Congress include requesting reports or briefings on U.S. flights through the ECS ADIZ, on preparations for aggressive interceptions of U.S. aircraft, and on U.S. support for allied countries' military aircraft in the ECS ADIZ. The U.S. military conducts Freedom of Navigation (FON) operations to challenge excessive maritime claims, in order to preserve the rights, freedoms, and uses of the sea and airspace under international law. The United States could reinforce its rhetorical response to China with air and naval patrols in the East China Sea, perhaps in combined operations with allies. S.Res. 412 (113 th Congress) affirmed that it is U.S. policy to "assure the continuity of operations by the United States in the Asia-Pacific region, including, when appropriate, in cooperation with partners and allies, to reaffirm the principle of freedom of operations in international waters and airspace in accordance with established principles and practices of international law."

			Accommodation and Assurance of China

Some scholars advocate attention to accommodation bilaterally to avoid a relationship with a more adversarial, assertive, or aggressive China with rising military power. Other scholars urge Washington to reassure Beijing, including by informing it in advance of legitimate U.S. military transits (though not necessarily particular flight plans) and to avoid flights by B-52 bombers in favor of fighters or patrol planes to assert the freedom of navigation and overflight in the ECS ADIZ. Congress could encourage expanded and comprehensive political, economic, and military engagement with the PRC to deal with tensions arising from episodes like the establishment of the ECS ADIZ. 

			Military-to-Military Contacts with China

Concerning U.S. military-to-military contacts with China, Congress has oversight of the President's adherence to laws that include the National Defense Authorization Act (NDAA) for FY2000 ( P.L. 106-65 ), which restricts military-to-military exchanges, and the Arms Export Control Act (AECA) (P.L. 90-629), which governs transfers of defense articles and defense services. U.S. defense officials have expressed a desire to continue or intensify communication with the PLA regarding the ECS ADIZ and other concerns. The Chief of Staff of the Air Force, General Welsh, said that the disagreement over the ECS ADIZ is an opportunity for better communication. PACOM Commander Admiral Locklear called the PLA's participation for the first time in the Rim of the Pacific (RIMPAC) maritime exercise at Hawaii in the summer of 2014 a "confidence-building measure" to help prevent miscalculation and promote peace. The Commander of the U.S. Pacific Air Forces, General Lori Robinson, attended China's air show in November 2014. On the other hand, some observers call for disengaging from the trajectory of closer military exchanges. A third view calls for Congress to retract restrictions in the FY2000 NDAA that constrain contacts with China's military and leave decisions to the executive branch about how to carry out exchanges with the PLA.

			Strategic Reviews of Policy

The PRC's designation of the ECS ADIZ again raises the question of whether the U.S. responses to the PRC's moves in maritime disputes have been effective and whether this development warrants a broad review for any changes in policy. Such attention is consistent with calls among some Members of Congress and observers for a clearer strategy to implement the Administration's "rebalance" to the Asia-Pacific in a coordinated, comprehensive way. Section 1251 of the National Defense Authorization Act (NDAA) for FY2015 ( P.L. 113-291 ) instructs the Secretary of Defense to develop a strategy to prioritize U.S. defense interests in the Asia-Pacific region. Section 1257 of the FY2015 NDAA requests an independent assessment of A2/AD strategies and capabilities that pose a threat to security in the Asia-Pacific region and strategies to mitigate such threats.
Another option for congressional oversight concerns the development of an inter-agency strategy for the rebalance to the Asia-Pacific region. Section 7043 of the Consolidated Appropriations Act of FY2014 ( P.L. 113-76 ) requires that the Secretary of State, in consultation with the Administrator of the U.S. Agency for International Development (USAID), the Secretary of Defense, and the heads of other relevant federal agencies, submit an integrated, multi-year planning and budget strategy for a rebalancing of U.S. policy in East Asia and the Pacific that links U.S. interests with the necessary resources and personnel required for implementation, management, and oversight of such a strategy.

			Crisis-Management and Confidence-Building Measures

Congress could call for U.S. efforts, perhaps in coordination with allies and partners, to test whether the PRC seeks stable ties and de-escalation of tension by suggesting crisis-management mechanisms or confidence building measures (CBMs). The U.S. Defense Department set up a direct defense telephone line (a hotline) with the PLA in 2008, after five years of negotiations. Vice President Biden visited Asia right after the ECS ADIZ announcement and stressed that the action underscored the need for China and Japan to establish CBMs to lower tensions. In 2012, military officials of the PRC and Japan discussed setting up a hotline to prevent air and naval crises, but the talks were suspended amid tension over the Senkaku Islands. Beijing resisted re-starting talks on a maritime communication mechanism and strongly criticized Tokyo, but the two sides eventually returned to negotiations following the meeting of Prime Minister Abe and President Xi in November 2014.
If negotiating new agreements is difficult, attention could be focused on implementing or adjusting existing agreements, or resuming previously held dialogues. Examples include an agreement of February 13, 2001, whereby the PRC and Japan agreed on a mutual notification system through which each side will notify the other prior to maritime research near the other country. The November 2014 U.S.-China MOU on the Rules of Behavior for Safety of Air and Maritime Encounters may be another model for China and Japan. Some China experts have questioned the utility of hotlines, because the PLA has been reluctant to hold direct discussions in times of international crises.

				One Model of International ADIZ Management: Japan-ROK Pact

Since 1995, Japan and South Korea have abided by a bilateral agreement to report in advance the flight plans of military aircraft that might stray into the other country's ADIZ. Reportedly, the two countries agreed on this notification pact in order to avoid accidental confrontations, build greater confidence between the two countries and their militaries, and obviate unnecessary scrambles. Such an agreement might be a practical way for East Asian countries to manage some of the negative consequences of their overlapping and contested ADIZs. However, it is unlikely that Japan and China would agree to reciprocal notification of military flights in the other country's ADIZ, because that could be construed as acceptance of the other's ADIZ.

			Recalibrating the U.S.-Japan Alliance

The United States may choose to recalibrate, in small but significant ways, its alliance relationship with Japan (and perhaps South Korea) partly in response to the establishment of the PRC's ECS ADIZ. Potential alliance adjustments could take the form of new military operational practices, official rhetoric, defense cooperation guidelines, or other policies. Before his April 2014 trip to Japan, President Obama announced, "The policy of the United States is clear—the Senkaku Islands are administered by Japan and therefore fall within the scope of Article 5 of the U.S.-Japan Treaty of Mutual Cooperation and Security. And we oppose any unilateral attempts to undermine Japan's administration of these islands." A Sense of the Congress in Section 1286 of the FY2013 NDAA ( P.L. 112-239 ) states, "The unilateral action of a third party will not affect the United States' acknowledgment of the administration of Japan over the Senkaku Islands." S.Res. 412 echoed this statement. U.S. officials could choose to consistently reiterate that Article 5 of the U.S.-Japan treaty applies to the Senkaku Islands and the surrounding 12-nm of sea and airspace. On the other hand, U.S. officials may also decide to keep ambiguous the conditions under which the treaty would apply. 
The ongoing revision of the U.S.-Japan Mutual Defense Guidelines, which provide a policy framework for security cooperation, could clarify U.S.-Japan combined activities in the East China Sea, including air operations in the disputed ADIZ. A small number of outside observers have suggested that the United States should consider recognizing Japanese sovereignty over the Senkaku islands as a way to provide clarity and to bolster the U.S.-Japan alliance. Another option would be to foster trilateral defense coordination among the United States, Japan, and South Korea, as a way to discourage provocative actions from the PRC (and North Korea). Still, policy makers might reserve options for the future after testing Beijing to see whether it is serious about lowering tension with other countries or is raising tensions to strengthen its stance, and whether China increasingly is acting in accordance with international laws.

			International Rules and Arbitration

Congress could urge the Obama Administration to focus on options that consider international rules or mechanisms for dispute resolution, including referral to the International Court of Justice. U.S. officials at the highest levels consistently raise concerns about the need for a rules-based, less confrontational international regime for both the South and East China Seas, including how the PRC might or might not set up another ADIZ. There are several forums available to arbitrate maritime territorial disputes, such as the Senkaku/Diaoyu islands dispute that arguably was the genesis of the ECS ADIZ. Yet, the principles governing the scope and application of ADIZs have not been defined in international law (see next section).

			Addressing ADIZs at ICAO

ICAO was created under the 1944 Chicago Convention to serve as the designated United Nations agency charged with matters pertaining to international aviation. ICAO develops international standards and recommended practices for aviation. In this capacity, ICAO appears to be the most appropriate authority for hearing concerns regarding the establishment of and procedural requirements for ADIZs. As previously noted, however, neither the Chicago Convention nor ICAO standards and recommended practices specifically address issues pertaining to ADIZs. The United States or any other member nation could petition ICAO or take a lead role in proposing and drafting a proposed ICAO standard or recommended practice pertaining to the establishment of ADIZs and flight operational procedures within a designated ADIZ. As a possible option, Members of Congress could urge that the U.S. Mission to ICAO work with other ICAO member nations toward a consensus agreement with regard to ADIZs. An international agreement could offer predictability and prevent the proliferation of ADIZs that increase the risks of conflict. However, U.S. accession to such an agreement could force changes in U.S. ADIZ practices and limit the scope for unilateral management of airspace near U.S. territory.
ICAO offers a process for international dispute resolution regarding matters pertaining to international aviation, including potentially the ongoing dispute over China's ADIZ. In December 2013, it was reported that Japan requested ICAO involvement in resolving the dispute over China's ADIZ. In March 2014, the United States and Japan formally submitted a letter to ICAO asking whether a country has the right to give orders to, or restrict the flights of, commercial aircraft in airspace outside the jurisdiction of its civilian air traffic controllers. As noted earlier, a large portion of the ECS ADIZ extends beyond Chinese-controlled FIRs, though that is not the only aspect of the ADIZ to which the United States and Japan have objected. A possible future course of action for countries opposing China's establishment of or procedural requirements for civil aircraft flying in its ECS ADIZ would be to file a formal complaint before ICAO in what is referred to as an Article 84 filing. Article 84 of the Chicago Convention establishes a formal ICAO process for settling differences among member countries.
Since ADIZs are not formally recognized under the Chicago Convention or international civil aviation law, there is no clear precedent for how ICAO may resolve such a complaint. The outcome may have important implications for international recognition of ADIZs globally, including long-established ADIZs, such as those maintained by the United States. Central issues for a possible international debate on ADIZs are likely to include the extent of ADIZ boundaries beyond territorial airspace, the applicability of ADIZ procedures to transiting aircraft not intending to enter sovereign airspace, and potential operational conflicts in areas where ADIZs overlap.

	Outlook

Although the issue of ADIZs is not central to U.S.-China relations or to China's overall foreign and defense policies, the PRC's actions regarding the ECS ADIZ and its decisions to designate (or not) other ADIZs will continue to shape perceptions of China and influence the narratives surrounding its rise to major power status. In particular, the PRC's handling of any new ADIZ, should it choose to designate one, will be watched very closely for what it says about Chinese attitudes toward its neighboring countries and toward the rules and norms of the existing international order. Congress and the executive branch likely will calibrate U.S. policy toward the PRC based in part on Beijing's actions in its maritime periphery, and the ADIZ issue now figures in that policy analysis. In a more narrow sense, the PRC's approach to the Senkaku/Diaoyu Island dispute will also influence how observers interpret the decision to designate the ECS ADIZ in late 2013. If China uses the ECS ADIZ as an instrument to increase pressure on Japan and the U.S.-Japan alliance, that may suggest that Beijing's goals were not defensive but rather coercive in nature.

		Appendix. Text of ECS ADIZ Announcement

The PRC MND issue the following statement on November 23, 2013:
The Ministry of National Defense of the People's Republic of China, in accordance with the Statement by the Government of the People's Republic of China on Establishing the East China Sea Air Defense Identification Zone, now announces the Aircraft Identification Rules for the East China Sea Air Defense Identification Zone as follows:
First, aircraft flying in the East China Sea Air Defense Identification Zone must abide by these rules.
Second, aircraft flying in the East China Sea Air Defense Identification Zone must provide the following means of identification:
1. Flight plan identification. Aircraft flying in the East China Sea Air Defense Identification Zone should report the flight plans to the Ministry of Foreign Affairs of the People's Republic of China or the Civil Aviation Administration of China.
2. Radio identification. Aircraft flying in the East China Sea Air Defense Identification Zone must maintain the two-way radio communications, and respond in a timely and accurate manner to the identification inquiries from the administrative organ of the East China Sea Air Defense Identification Zone or the unit authorized by the organ.
3. Transponder identification. Aircraft flying in the East China Sea Air Defense Identification Zone, if equipped with the secondary radar transponder, should keep the transponder working throughout the entire course.
4. Logo identification. Aircraft flying in the East China Sea Air Defense Identification Zone must clearly mark their nationalities and the logo of their registration identification in accordance with related international treaties.
Third, aircraft flying in the East China Sea Air Defense Identification Zone should follow the instructions of the administrative organ of the East China Sea Air Defense Identification Zone or the unit authorized by the organ. 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.
Fourth, the Ministry of National Defense of the People's Republic of China is the administrative organ of the East China Sea Air Defense Identification Zone.
Fifth, the Ministry of National Defense of the People's Republic of China is responsible for the explanation of these rules.
Sixth, these rules will come into force at 10 a.m. November 23, 2013.

Summary:
In November 2013, the People's Republic of China (PRC, or China) announced that it would establish an "East China Sea Air Defense Identification Zone (ADIZ)," covering a large swath of airspace over the East China Sea, including over small islands that are the subject of a territorial dispute among Japan, the PRC, and Taiwan. Beijing did not formally consult with other countries prior to the announcement, and its initial statement seemed to warn that China might use force against aircraft that did not follow its ADIZ guidelines. Senior officials from the United States and East Asian countries criticized China's action and raised concerns that the new ADIZ could escalate tensions surrounding the territorial dispute and even lead to conflict.
Some key considerations for Congress are the potential for military conflict in the East China Sea, escalation of tensions over the territorial dispute, challenges to the U.S.-Japan alliance, and the impact on U.S.-China relations, including military-to-military exchanges.
An ADIZ is an area of airspace beyond a country's sovereign territory within which the country requires the identification, location, and air traffic control of aircraft in the interest of its national security. There is no international law that specifically governs ADIZs, although various norms pertain, especially freedom of navigation. The Convention on Civil Aviation advises that all nations refrain from the use of weapons against civilian aircraft. The United States was the first country to establish an ADIZ, which it did in 1950 during the Cold War with the Soviet Union.
There are several possible reasons why the PRC designated its "East China Sea ADIZ" (ECS ADIZ). The ADIZ appears to be part of an effort by China to challenge Japan's administration of the disputed islands, known as Senkaku in Japan, Diaoyu in China, and Diaoyutai in Taiwan. The ECS ADIZ may also be intended as a means to bolster both China's own claims to the islands and its justification for opposing U.S. military surveillance activities near its airspace. In the initial period after the PRC announcement, the PLA did not take "defensive emergency measures" against aircraft that ignored the Chinese ADIZ directives.
In addition to criticisms by the U.S. Secretaries of State and Defense that the ECS ADIZ was "destabilizing" and increased the risks of conflict in the region, the United States announced that it "neither recognizes nor accepts China's declared East China Sea ADIZ." As of early 2015, the U.S. military continues to fly aircraft through the zone without notifying China or responding to requests for identification. The Federal Aviation Administration (FAA), however, distributed China's requirements for operating in the ECS ADIZ to commercial airlines as part of its routine dissemination of Notices to Airmen (NOTAMs).
Japan, South Korea, and Taiwan each voiced opposition to China's designation of the ECS ADIZ, which overlapped with their pre-existing ADIZs, and have continued normal military practices in the zone. South Korea requested that China redraw the boundary to remove this overlap, but Beijing refused the request, prompting Seoul to extend the boundaries of its ADIZ in December 2013. Japan called the PRC's action an attempt to change the status quo on the Senkaku Islands by coercion. The U.S.-Japan Mutual Defense Treaty applies to the Senkaku Islands because they are administered by Japan.
This report analyzes the legal, diplomatic, and security implications of the ECS ADIZ for U.S. interests. The concluding section briefly discusses some policy options for Congress and for U.S. policy in general.