The East China Sea: A Case of Ocean Geopolitics and Maritime Conflict

Abstract

This article analyzes ECS maritime disputes through two lenses: as a globally comparable case study mediated through LOS and as a distinct regional case that differs in several respects from disputes outside East Asia. This study focuses on the Senkaku/Diaoyu island dispute but also examines broader EEZ and ADIZ disputes between China, Japan, and South Korea and the Ieodo dispute between China and South Korea. It finds that global dynamics are applicable to the ECS disputes, as countries depend on LOS rules even while attempting to interpret them for unilateral advantage whenever possible, and parties avoid formal arbitration, when possible, in favor of bilateral agreements. However, regional factors impact these dynamics. The sudden and sometimes violent transition from the Sino-Centric tributary system to the Westphalian system has undermined the legitimacy of LOS and western international law regionally. Finally, the presence of China as a party to almost all ECS disputes limits the application of LOS because China’s position as a near-peer competitor with the US gives it additional options to unilaterally impose its will. Unlike relatively weaker parties to these disputes, China may be less concerned about flouting LOS that it does not see as necessary for protecting its maritime claims.

Introduction

Maritime disputes worldwide are attracting scholars and the media. With the increasing pressure on oceans owing to climate change, pollution, and resource requirements driven by improved extraction and survey technology, maritime disputes in domains enclosed by multiple countries, such as the Mediterranean Sea, Black Sea, Arctic Ocean, or Caribbean Sea, have increased the potential for conflict [1]. Perhaps, this is nowhere more apparent than in East Asia.

Disagreements and disputes in both the South China Sea (SCS) and East China Sea (ECS) have attracted media and researchers for the past few decades. However, there are two limitations in the literature and discussion on these regional disputes. First, there is a lack of detailed examination of each dispute and its specific characteristics while maintaining a regional approach focused on each dispute as part of a larger maritime regional complex. Second, there is limited linking of region-specific or even dispute-specific findings and tendencies with larger global trends, as this relates to ocean geopolitics and maritime disputes.

In this article, we focus on both limitations by examining a region that has received considerable attention for maritime disputes and the chance of conflict at sea—the ECS—and by linking regional characteristics with the larger global phenomena of maritime boundary disputes. First, what are the specific features defining contemporary maritime disputes related to islands, boundaries, and—by extension—sovereign rights in the ECS? Second, how do these regional features link to global maritime issues and disputes?

Primarily, this qualitative study is based on historical and legal approaches that help describe the intricacies and history of each dispute in the ECS. Data are obtained from primary official sources, such as treaties, official documents, and statements, by countries and their officials, in addition to secondary sources, such as academic publications, media reports, and other analyses. The historical approach is combined with a political scientist’s tendency to generalize and identify commonality among disparate cases. Moreover, we focus heavily on legal analyses and approaches when determining the complexities of maritime disputes and their linkages to the Law of the Sea (LOS).

Although we examine the complexity of the ECS, one dispute attracts more attention than others, namely, the sovereignty of the Senkaku/Diaoyutai/Diaoyu islands. We focus on this because it is the only dispute over an above-high-tide geographic feature (unlike the Socotra subsea surface rock dispute); it is a three-way dispute, and it has the highest possibility for conflict.

By looking at the ECS, it is apparent that global dynamics are applicable to the ECS dispute. In particular, countries tend to depend on norms and rules of LOS even while attempting to interpret them to their unilateral advantage whenever possible. The parties to these disputes avoid formal arbitration when possible in favor of bilateral agreements. Furthermore, the settlement and management of these disputes have become complicated owing to growth in recoverable resources because of technological advancements and increasing the salience of maritime disputes in domestic politics for reasons of national identity and nationalism, as well as the economic stakes involved.

However, additional distinctive regional factors impact these dynamics. In the nineteenth century, the sudden and, in certain instances, violent transition from the Sinocentric tributary system to the Westphalian state system has challenged the legitimacy of LOS and Western international law to a certain extent. Moreover, it has prompted parties to these disputes to seek out pre-Westphalian historical documents, as well as other artifacts, to attempt to press their maritime claims. These facts have made parties even more reluctant than states elsewhere to agree to arbitration and even to reject the very legitimacy of LOS arbitration mechanisms in some cases.

This has been particularly evident for China but is not exclusive to China. Finally, the presence of China as a party to almost all ECS disputes may limit the actual application of LOS because China’s position as a near-peer competitor with the US gives it additional options to unilaterally impose its will in these disputes. Unlike other weaker parties involved in these disputes, China has less structural incentive avoid flouting laws and norms that it does not see as necessary for protecting its maritime claims. Indeed, as an emerging superpower, China may be seeking to at least partially remake the international law, including LOS, to reflect its interests better—a factor that makes the ECS and SCS maritime conflicts distinct from those in other regions.

The rest of this article will consist of six sections. The next section will outline the primary characteristics of the ECS. The following section will examine the Senkaku island dispute between China, Japan, and Taiwan. The section after that will examine Sino-Japanese disputes over their EEZ and ADIZ boundaries, and the section after that will briefly the Socotra rock dispute between China and South Korea. These sections will answer our first research question, namely what are the specific features defining contemporary maritime disputes related to islands, boundaries, and—by extension—sovereign rights in the ECS? The next section places ECS disputes in the context of global trends regarding maritime conflicts and their resolution. The following section analyzes how global trends impact the ECS disputes along four dimensions, and adds two dimensions distinct to the ECS and how those impact maritime disputes in that body of water. These two sections thereby address our second research question, namely, how do these regional features link to global maritime issues and disputes?

The East China Sea

ECS is the body of water bordered by the Chinese coast to the West, South Korea to the Northeast, and Japan (including the Ryukyu Islands) and Taiwan to the East. ECS is separated from SCS by the Taiwan Strait, as well as from the Sea of Japan by the Tsushima and Korean Straits. Disputes in the ECS are over the Senkaku/Diaoyutai/Diaoyu Islands, over Socotra Rock, and over the overlapping exclusive economic zone (EEZ) claims between China and Japan, as well as China and South Korea.

The countries bordering the ECS are diverse. China, located to the west, is a one-party communist state. To the North, East, and South are the liberal democracies of South Korea, Japan, and Taiwan (Republic of China, ROC). While South Korea and Japan are US allies, China has emerged as the second pole in a bipolar or multipolar international system and hence is a peer competitor to the US [2]. Except for Taiwan, all the littoral states are members of the UN and regional multilateral organizations, such as the ASEAN Regional Forum, ASEAN Plus Three (APT), ASEAN Defense Ministers Plus Dialogue Partners, Expanded ASEAN Maritime Forum (EAMF), and East Asian Summit. All of these multilateral forums are helpful for managing, if not resolving, maritime disputes and military tensions related to ECS. China, Japan, and South Korea are members of the subregional Trilateral Cooperation Mechanism (TCM), which promotes cooperation among these three Northeast Asian states and includes security cooperation (mostly non-traditional security cooperation).¹

The ECS Disputes and Their Regional Context

The most pressing territorial dispute is over the Senkaku/Diaoyutai/Diaoyu Islands, followed by the Sino–Japanese dispute over where to draw the line for their respective EEZs. The Sino–South Korean dispute over Socotra/Ieodo Rock, as well as EEZ disputes between South Korea and China, are far less prominent. The overlapping air defense identification zones (ADIZs), which include cases of one country’s ADIZ covering another country’s claimed EEZ, are potentially complicating these EEZ disputes.

The issue of Taiwan’s status as an independent state or as a part of China is excluded from this analysis because it is arguably an issue of national reunification or independence and not a maritime dispute. Accordingly, tensions between Taiwan and China over the islands of Quemoy and Matsu, which are held by Taiwan but came under attack from mainland China during the Cold War, are excluded from this survey. Because these islands are extremely close to the Chinese mainland and in the Taiwan strait, they are arguably on the edge, if not outside the ECS.

The Senkaku Dispute

The first dispute concerns the Pinnacle Islands, called the Senkaku Islands (尖閣諸島) by Japan, the Diaoyutai/Tiaoyutai Islands (釣魚臺列嶼) by Taiwan, and Diaoyu Island and its affiliated islands (钓鱼岛及其附属岛屿) by China. The largest Senkaku Island is Uotsuri Island (魚釣島 by Japan, 釣魚台 by Taiwan, 钓鱼岛 by China);² it is 3.6 km² in area. The next largest island is called Kuba (久場島) by Japan, Huangwei (黃尾嶼) by Taiwan, and Huangwei Yu (黄尾屿/黄尾嶼) by China; it is 0.87 km² in area. The combined area of the next six islands (geographic features) that form the Senkaku Islands is <1 km² [3].

None of these islands, including Uotsuri, has a natural fresh (drinkable) water supply and they are not populated [4], although there was a small Japanese settlement on Uotsuri (associated with a fish processing facility) during the first several decades of the twentieth century. In the 1960s, fishermen and salvage workers from Taiwan occasionally resided temporarily on these islands. The islands’ resources include guano (bird excrement that can be used to fertilize crops) and fishing; they are unsuitable for agriculture [5].

Under UNCLOS, these islands do not qualify for their own EEZ because they cannot naturally support human habitation (Article 121).³ Moreover, because these islands are already within the overlapping EEZ claims of both China and Japan, even a finding that they are entitled to an EEZ would possibly have little practical impact on where EEZ boundaries are drawn. However, because these islands are above high-tide geographic features, they qualify for the 12 NM of territorial waters. Although the Senkaku Islands essentially have nothing in terms of economic resources apart from fishing, they do have ecological value in their pristine undeveloped state. In particular, the Senkaku Islands host a diverse range of birds, including the rare short-tailed albatross. BirdLife International recognizes the Senkaku Islands as an Important Bird Area [6, 7].

The Sinocentric Tributary System

The dispute between China, Japan, and Taiwan is primarily based on historical claims dating back to the Sinocentric system of international relations that managed the international relations of East Asia for centuries before the arrival of Western imperial powers in the mid-nineteenth century.⁴ During this period, these islands were between Imperial China and the Ryukyu Kingdom, based in Okinawa. Both countries reportedly used these islands as navigational aid. Japanese pirates (Wako, although frequently multinational with Chinese elements) used the remote and barren Senkaku Islands as a base for launching attacks on shipping [8]. Under the Sinocentric tributary system, these islands were a remote and unpopulated territory in the border zone between China and the Ryukyu Kingdom. Unlike the Westphalian international state system, which is characterized by precise borders and division of all land territories among states, the Sinocentric tributary system featured border and buffer zones rather than precise borders. There was a vacuum of pre-Westphalian record of state actions that easily comport with Western international legal standards for asserting sovereignty, particularly as neither China nor the Ryukyu Kingdom claimed the Senkaku/Dioayu Islands as their territory [8].

Westphalia and Imperialism

After Japan entered the Westphalian state system, it used pirate attacks on the Ryukyuan kingdom in 1875 as a pretext under Western international law to annex Ryukyu [9].⁵ This annexation led Imperial Japan into proximity to the unpopulated Senkaku Islands. In Japan, there were multiple proposals during the 1880s and early 1890s to annex the Senkaku Islands; however, no action was taken out of fear that this would provoke a conflict with China. Nevertheless, during the Sino–Japanese War of 1894–1895, on January 14, 1895, three months before the war ended, Japan annexed the Senkaku Islands, claiming that they were terra nullius. In the subsequent peace treaty of Shimonoseki, China gave to Japan “the island of Formosa, in addition to all islands appertaining or belonging to the said island of Formosa.” [7, 8].

To date, these two facts are central to the sovereignty dispute. Article 2 of the 1952 San Francisco Peace Treaty required Japan to surrender all territories it had acquired via the Sino–Japanese War of 1894–1895, including Taiwan.⁶ For the ROC, and then for the People’s Republic of China (PRC), this indicated that the Senkaku Islands had to be returned to China because they were a part of Taiwan and had been taken owing to Japan’s aggression in the Sino–Japanese War, as per the Shimonoseki treaty. In Japan’s view, however, these islands had been annexed because they were terra nullius, and this act, although happening during the Sino–Japanese War, was unrelated to it [8].

Another limitation was the legitimacy deficit of Western international law owing to the unequal treaties imposed on China and Japan, as well as the colonization of other Asian states by Western imperial powers with Japan eventually joining in. “Reclaiming” the Diaoyu Islands has become a symbol for China of throwing off a “century of humiliation” that the country experienced after the imposition of Western international law [10].

Japan maintained control of the Senkaku Islands from 1895 until 1945, a period that coincided with the colonization of Taiwan. At the end of World War II, Japan surrendered control of Taiwan to the Republic of China, and then the US took control of the Senkaku Islands along with the Ryukyu Islands. The Senkaku Islands remained under US administration until the return of Okinawa in 1972. In that period, the US used two of the smaller Senkaku Islands as bombing ranges and left the islands otherwise untouched. Fishers from Taiwan frequently, and occasionally government-affiliated ships from Taiwan or the PRC, showed up in the waters around the Senkaku Islands. ROC ship salvagers on at least one occasion in the late 1960s resided for a few months in tents on these islands. However, the US exercised administrative, if not always effective, control over these remote islands [11].⁷

Okinawa Reversion

In the late 1960s, three events occurred simultaneously. First, Japan and the US reached an agreement for the reversion of Okinawa to Japanese sovereignty. Previously, during negotiations, a compromise was then reached in what would become the 1960 Japan-US Security Treaty (which remains in effect to this day), which indicated that, under Article 5 of the Treaty, the US committed to defending territories under “the administration of Japan” (i.e., Japan’s four main islands and subsidiary islands under its control). This language would have considerable implications for the dispute over the Senkaku Islands decades later.

Second, during the late 1960s, when the US reversion of Okinawa and Ryukyu Islands to Japan became clear, the Emery survey of May 1969 that covered ECS and was sponsored by the UN-funded Economic Commission for Asia and the Far East, reported potentially rich deposits of oil and gas in the East China seabed, including several dozen kilometers beyond the territorial waters of the Senkaku Islands. Third, in September 1970, the ROC claimed sovereignty over the Senkaku Islands. Subsequently, Japan issued its own formal claim of sovereignty over these islands. Shortly thereafter, following the ROC’s lead, the PRC claimed sovereignty over these islands [7].

The Emery survey has become an important talking point because those supporting Japan’s claim often argue that both the ROC and PRC were motivated to claim sovereignty over the Senkaku Islands merely because of the discovery of potential hydrocarbon deposits nearby; thus, as an act of economic opportunism. However, in November 1969, the announcement of an agreement between Japan and the US regarding the return of Okinawa and the Ryukyu Islands to Japanese sovereignty appears to have been as much, if not a more, important a motivation. The ROC—a US ally with American troops then stationed on its soil—had not pressed a sovereignty claim against the US control of these islands, particularly as two of them had been used as a bombing range that presumably contributed to Taiwan’s defense. Indeed, Taipei clarified that while it did not object to the US administration of these islands or the Ryukyu Islands, it did not view Japan as having any rights to the Senkaku Islands, and it questioned Japan’s “residual sovereignty” over the Ryukyu Islands.⁸ The timing of Taiwan’s claim to the Senkaku Islands can be linked to the possible return of the Okinawa and Ryukyu islands to Japan, which the ROC objected to as much, or perhaps even more, than it can be linked to the discovery of oil and gas in nearby waters. Moreover, it has never been clear, especially after UNCLOS was concluded in 1982, that sovereignty over the Senkaku Islands would confer any right to develop the hydrocarbon resources of the ECS beyond the 12 NM territorial waters that these islands have, an area probably too small to hold considerable hydrocarbon resources.

In 1972, the US returned the Senkaku Islands, which it had seized from Japan by force in 1945, to Japanese control. The US adopted a position of neutrality regarding sovereignty over these islands. The US’s position was summarized by a State Department legal expert: “The United States cannot add to the legal rights that Japan possessed before it transferred administration of the islands to us, nor can the United States, by giving back what it received, diminish the rights of other claimants.”⁹

The Sino–Japanese Tacit Management Regime

With the reversion of Okinawa and the Ryukyu Islands from the US to Japan in 1972, the Senkaku Islands emerged as an irritant in relations between China, Japan, and Taiwan. Sino–Japanese relations were established in 1972; the two sides then commenced negotiations on a peace and friendship treaty, during which the territorial dispute over these islands came up. In April 1978, during the final phases of negotiations, China sent a flotilla of approximately 100 fishing boats to the Senkaku Islands in a show of force. In the end, the 1978 Sino–Japanese Treaty of Peace and Friendship did not resolve this issue. The Chinese leader, Deng Xiaoping, proposed that the territorial issue be “shelved.”¹⁰ Japan accepted this statement but without publicly endorsing it.¹¹ Apparently, Japan misperceived this statement as a de facto Chinese recognition of Japanese sovereignty [7]^.

However, after the conclusion of the 1978 Treaty of Peace and Friendship between China and Japan, the two tacitly cooperated to ensure that bilateral tensions over the Diaoyu/Senkaku islands did not damage the overall bilateral relations, especially economic relations. For example, bilateral cooperation in fisheries was insulated from the bilateral territorial dispute; fishing around the islands (as per the 1975 and 1997 bilateral fisheries agreements) was defined as a fisheries issue, not a territorial one. This approach was part of a tacit bilateral conflict management regime.

This conflict management regime was based on China’s de facto recognition of Japan’s control of the Senkaku Islands in exchange for a Japanese promise to leave these islands unoccupied and undeveloped. Japan tacitly agreed to China’s three nos: no entry, no survey, and no use, including no development. In exchange, China tacitly agreed to Japan’s three nos: no landing, no entry into islands’ airspace, and no entry into their waters [12]. In addition to the 1997 agreement on fisheries in the surrounding waters, other resources were left undeveloped and unexplored, especially hydrocarbon resources. With the flaring up of this issue, both countries acted to quickly diffuse tensions and insulate the rest of the relationship [13]. However, the dispute flared up several times between 1978 and 2004. These flare-ups challenged both governments and were driven by civil society groups in Japan, Hong Kong, Taiwan, and increasingly from China in later years [7, 14, 15].

Breakdown of Conflict Management Regime

In September 2010, a Chinese fishing boat collided with two Japanese Coast Guard (JCG) vessels in the territorial waters of the Senkaku Islands, thus setting off a sharp bilateral dispute as Japan arrested the boat’s captain and moved to try him under Japanese law [16]. The captain’s arrest was the first time that Tokyo had applied Japanese domestic law in waters around these islands, and the Democratic Party of Japan (DPJ) was apparently unaware of the previous Liberal Democratic Party governments’ policy of not doing so and was unaware of other aspects of the tacit conflict management regime [16, 17]. China rejected Japan’s jurisdiction to indict the captain, citing its own territorial claims to the Diaoyu/Senkaku islands. Eventually, the captain was released without charge after considerable pressure from the Chinese [18], an outcome that led to recriminations against the DPJ Kan cabinet in Japan, as well as a determination to be uncompromising in the future.

The 2010 crisis was a prelude to a far more serious crisis in April 2012, when the nationalist governor Ishihara Shintarō proposed buying the Senkaku Islands from their private Japanese owner and developing them. He justified this initiative by claiming that the DPJ was not doing enough to ensure effective Japanese control of these islands. Ishihara’s proposal promised to completely overturn the 1978 conflict management regime, that is, the status quo of Japanese control but non-occupation, a development that would be exceptionally provocative for China. The Noda cabinet responded by purchasing the remaining private property rights on the Senkaku Islands in September 2012 [19].

Although the Noda cabinet’s decision was intended to preserve what remained of the 1978 regime, it, however, provoked China, who saw the purchase as another attempt by Japan to overturn the status quo by exercising Japanese law over these islands. In early September, China took the nearly unprecedented step of sending multiple government maritime patrol vessels into the territorial waters of the Diaoyu/Senkaku islands, a move Beijing justified as enforcing “China’s jurisdiction over the Diaoyu Islands and ensuring the country’s maritime interests.” The next day, the largest anti-Japanese protests since bilateral relations were normalized swept through 50 cities in China. For the first time, Japanese-owned factories were attacked and damaged. A mass boycott movement of Japanese goods was organized in China; it lasted for several months and was surprisingly effective, and reportedly lowered Japanese economic growth in fiscal year 2012 by approximately 0.6% [19, 20].

The confrontation that began in September 2012 continued after the end of the Noda administration and DPJ rule in late December 2012 and has become the new normal to date. It effectively replaced the collapsed 1978 conflict management regime with the new status quo. Long after the unprecedentedly large “Defend Diaoyu” (Bao Diao) demonstrations in Chinese cities, and even after the Chinese boycott of Japanese goods had ended, the confrontation continued in the waters around the Diaoyu/Senkaku islands as China continued to regularly send its coast guard vessels into the territorial waters of these islands, thereby challenging Japan’s effective control. The size and frequency of Chinese patrols through the territorial waters of the Senkaku Islands rose and fell with time, leading certain observers to argue that China has been using the frequency of its patrols for tacit signaling purposes [21] (Fig. 1).

Fig. 1

Incursions into Senkaku Territorial and Contiguous Waters by Chinese Government Ships per Month. Source: Japan’s Ministry of Land, Infrastructure & Transportation, as accessed at https://www.mofa.go.jp/region/page23e_000021.html

The long-term confrontation that has emerged since September 2012 has come not only to dominate Japan’s China policy, but it has also come to dominate Japan’s overall defense policy. The clearest indicator of Japan’s response to China regularly sending coast guard vessels into the waters around the Senkaku Islands is Japan’s formation of a new JCG flotilla. The flotilla comprises 12 ships, 10 new 1500-ton fast patrol ships armed with 20-mm guns and water cannons, and two refurbished helicopter-carrying vessels that were transferred from other JCG regions. In comparison, the remainder of the JCG’s Okinawa Division comprises only six vessels larger than 1000 tons and one helicopter carrying patrol vessel for operations other than protecting the Japanese control of the Diaoyu/Senkaku islands. Of the 1722 JCG members assigned to the Okinawa Division, 606 are exclusively assigned to protecting these islands. A base comprising piers, barracks, and other facilities has been built for this flotilla on Ishigaki Island [22]. The size of the Senkaku flotilla demonstrates the extremely high priority Japan places on defending its control of these uninhabited islands.

Taiwan and the Diaoyu/Diaoyutai Dispute. As mentioned previously, Taiwan formally placed the claim for the Senkaku Islands before the PRC in September 1970 [7]. Taiwan claims that the Senkaku Islands are a natural geographical extension of Taiwan. Because of Taiwan’s increasingly isolated international status and China’s growing role and presence after the late 1970s, as well as the relative naval and overall military power imbalance in favor of Japan during that period, Taiwan has not been extremely active in attempting to physically assert its territorial claims, although there have been certain exceptions.

In fact, in September 2012, Taiwan, similar to China, strongly protested the Japanese government’s decision to purchase and nationalize the remaining privately owned land on the Senkaku islands from their Japanese owner. In response, 10 Taiwanese CG cutters escorted 75 Taiwanese fishing vessels into the territorial waters around the Senkaku Islands and came within 3 NM of the Senkaku Islands. Interestingly, 10 JCG vessels met this flotilla and used water cannons against some of the Taiwanese fishing vessels, which prompted the Taiwanese CG vessels to fire water cannons on the Japanese ships and physically block them from getting close to the Taiwanese fishing vessels. Moreover, the Taiwanese CG vessels deflected small JCG boats that attempted to ram and seize the Taiwanese fishing vessels and arrest their crews. Taiwanese CG ships were supported in the background by two Taiwanese naval frigates and several F-16 and Mirage 2000 fighter jets that conducted reconnaissance [23,24,25].

However, only seven months later, Japan and Taiwan concluded a bilateral fishing agreement, although the agreement took 17 years to negotiate. Similar to the Sino–Japanese fishing agreements, fishing in the zone south of 27°N latitude was governed by the flag state, whereas fishing boats were exempted from the jurisdiction of the other state’s law enforcement. However, the territorial waters of the Senkaku Islands were excluded from this agreement. The two sides then agreed to hold discussions on developing common fishing rules for managing fishing stocks. Apparently, Japan pushed to conclude this agreement in the wake of Taiwan’s show of force on the Senkaku Islands in September 2012 to preclude a Taipei–Beijing united front against Japan’s control of the Senkaku Islands. Furthermore, Taiwanese President Ma Ying-jeou proposed an East China Sea Peace Initiative, which called on all parties to shelve sovereignty claims and jointly develop resources in the disputed waters [26].

In June 2020, the Japan-friendly administration of Taiwanese President Tsai Ing-wen reiterated Taiwan’s sovereignty claims over the Diaoyutai/Senkaku islands after the city of Ishigaki—in Japan’s Okinawa Prefecture, which has jurisdiction over the Senkaku Islands—moved to change the islands’ administrative designation. This move by Ishigaki was interpreted as another attempt to demonstrate Japan’s effective control over these islands by exercising Japanese law there. Although Tsai Ing-wen was promoting pro-Japan policies, in terms of domestic politics, it is difficult for her to give up Taiwan’s sovereignty claims over the islands [27].

Sino–Japanese EEZ and ADIZ Disputes

The EEZ Dispute

China and Japan proclaimed overlapping EEZ claims in the ECS in 1996, with China making a natural prolongation of its continental shelf claim, while Japan claimed a midpoint line between the two sides drawn from baselines from Kyushu via the Amami and Ryukyu islands. For the bilateral tacit conflict management regime around the Senkaku Islands, Japan avoided drawing baselines around the Senkaku Islands, although doing so would not have considerably enhanced Japan’s EEZ claim in any case.

Both sides’ UNCLOS claims have weaknesses. UNCLOS does not allow continental shelf claims when they overlap with another country’s 200 NM EEZ claim drawn from a coast; it only allows them when the continental shelf exceeds 200 NM. However, some of Japan’s baselines are drawn over open water, namely, the Miyakojima Strait, which is 135 NM wide, which can be problematic [7, 28]. Both China’s and Japan’s EEZ claims overlap with those of South Korea, which extends its EEZ claim southward by making a continental shelf claim, although arguably inconsistently, as it makes a median line claim in the Yellow Sea [29, 30].

However, China and Japan have proven capable of cooperating to manage their conflicting EEZ claims, especially around fisheries, if less so in the area of exploiting hydrocarbon resources. Building on the 1955 and 1975 bilateral fisheries agreements, China and Japan negotiated a new fisheries agreement in 1997. Similar to the two previous agreements, waters around the Senkaku Islands, specifically waters south of 27°N latitude, were excluded in the 1997 agreement, with the two sides unilaterally managing their own fishing activities in those waters, and not applying their own laws to each other’s fishing vessels in waters surrounding these islands. North of 27°N, the 1997 agreement established a preliminary measures zone (PMZ) in the middle of the ECS, drawing 52 NM from the coastal baselines of these two countries (Fig. 2). The two countries jointly managed the PMZ primarily by annually setting catch quotas for the two sides. Chinese fishers usually receive approximately three times the catch limit that Japanese fishers receive. Unlike the 1975 agreement, the 1997 agreement gives Japan authority to regulate Chinese fishing vessels in its coastal waters, i.e., within its claimed EEZ, except for the PMZ and waters around the Senkaku Islands south of 27°N [7]. To summarize, James Manicom argues that “the 1997 China-Japan fisheries agreement should be viewed as a successful attempt to share jurisdiction in contested waters,” despite the 2010 confrontation over the Senkaku Islands and the ongoing conflict there since 2012 and unlike the more violence-prone fishing relationship between China and South Korea.[7]¹²

Fig. 2

The Sino–Japanese Fishing PMZ. Source: [7]

Competing Trilateral EEZ Claims

One complication of the 1997 bilateral Sino–Japanese fishing agreement is that the northern part of the PMZ overlaps with South Korea’s EEZ claim. A year after the 1997 Sino–Japanese agreement, a Sino–South Korean Agreement on fisheries was reached that established transitional zones (TZs) and a provisional waters zone (PWZ) between them, which is supposed to ensure the cooperative management of these waters until the EEZ border can be determined. At the southern edge of the Korean TZ and the Sino–South Korean PMZ, as well as in waters further south, South Korea’s claims overlap with the northern edge of the Sino–Japanese PMZ. The two sets of bilateral fishing agreements in the ECS have not been parlayed into a trilateral fishing agreement owing to resistance among the three for doing so. This has created a gap in the management of migratory fishing stocks that could also contribute to depletion [7, 29, 31].

However, since 2017, the TCM, an organization growing out of the APT process, and more specifically out of the Northeast Asian Summit, has been promoting trilateral cooperation in fisheries. In particular, the TCM has sponsored three “Nongovernmental Fisheries Agreement Meetings” in 2017, 2018, and 2019 [32]. Moreover, the TCM has sponsored nearly a dozen Trilateral Fisheries Institutes’ Head Meetings [32] and more than a dozen trilateral workshops on jellyfish [32]. The TCM appears to be the most promising platform for developing deeper trilateral cooperation on fisheries in the ECS, although the APT and EAMF could also be used [33].

Sino–Japanese Conflict over Hydrocarbon Exploitation

At the turn of the century, China and Japan found themselves in conflict over the natural gas fields that China discovered in 2001, specifically the Chunxiao gas field (as called by China)/the Shirakaba gas field (as called by Japan), which is located just 5 km inside China’s side of what Japan claims should be the median line border between the two countries’ EEZ claims; a line far west of China’s claimed continental shelf. In May 2004, tensions rose when China started drilling operations in the Chunxiao gas field.

Japan then responded by hiring a Norwegian ocean survey ship, the Ramform Victory, to survey the eastern side of its claimed median line between June 2004 and January 2005. On at least one occasion, China dispatched two destroyers to tail the Ramform Victory when it was surveying just east of Japan’s claimed median line near the Chunxiao gas field. This prompted Japan to send two Maritime Self-Defense Force (MSDF) P-C3 maritime patrol planes to observe the situation. Ramform Victory’s report, published in February 2005, reported a “high probability” that the Chunxiao gas field extended into Japan’s side of its claimed median line, and thus China was in a position to siphon off gas from Japan’s claimed EEZ. These tensions prompted Shell and Unocal to exit from their participation in China’s development of the gas field [7, 34].

Subsequently, Japan decided to open bidding for drilling concessions on its side of the claimed median line. China responded with veiled threats to use force to stop drilling. In July 2005, Japan gave Teikoku Oil the drilling license, and China responded with heightened warnings with a Chinese embassy spokesman in Tokyo claiming Japanese oil and gas exploration in the disputed area east of Japan’s claimed median line would be considered “an invasion of Chinese territory” and “a highly provocative act”. In September 2005, five Chinese naval vessels were sent to the Chunxiao gas field in a show of force; one Chinese destroyer trained its guns (but apparently not its fire-control radar) on a passing Japanese P-3C maritime patrol plane. Japan then responded by asking China to cease its activities at the Chunxiao gas field, or Japan would proceed with its own exploratory drilling [7, 34, 35].

Eventually, China delayed the development of the Chunxiao gas field. Moreover, Japan passed its “Basic Ocean Law” in April 2007 (just as Chinese Prime Minister Wen Jiabao was visiting Japan), a law that created a legal framework for defending Japanese economic activities in its claimed EEZ against non-state and state actors, including China. However, during Wen’s meeting, progress was reportedly made toward a joint development agreement, and the two sides concluded such an agreement in June 2008. In particular, this agreement called for the creation of a 2700-km joint development zone (JDZ) that largely bisected Japan’s median line and south of China’s Longjing field (Fig. 3). Moreover, it allowed Japanese companies to invest in the Chunxiao gas field based on applicable Chinese laws. The agreement called for a bilateral treaty to be concluded to implement the agreement, which was a compromise in that Japan de facto conceded jurisdiction over the Chunxiao gas field to China, and China de facto recognized Japan’s claimed median line [7, 34, 36].

Fig. 3

The Sino–Japanese joint development zone in the ECS. Source: [7]

In 2008, talks on concluding a bilateral treaty made progress during the then Japanese Prime Minister Fukuda Yasuo’s tenure (who enjoyed a good relationship with Chinese leaders) but were stalled afterwards. Moreover, the agreement was considerably undermined by the September 2010 Senkaku Islands confrontation. There was consternation in Tokyo that Beijing appeared to respond to the September 2010 confrontation over the Senkaku Islands by beginning natural gas extraction from the Chunxiao gas field. Although from Japan’s understanding of the bilateral agreement, development was supposed to be suspended until the two sides concluded a treaty on co-development. As Streich notes, as of 2017, China operates 16 platforms just west of Japan’s claimed median line, pumping out gas (and perhaps siphoning it off from Japan’s side), while Japan has not set up any platforms or extracted any gas on its side of the line [34, 37]. Unlike the cooperation in fisheries, Sino–Japanese cooperation in hydrocarbon extraction in areas where the two countries’ EEZ claims overlap has not been successful to date.

China’s New ADIZ

Maritime tensions were exacerbated by China’s announcement of an ADIZ for the first time over a large portion of the ECS in November 2013. China’s new ADIZ considerably overlaps with Japan’s ADIZ, which the US created in 1969 before the reversion of Okinawa. One of the more surprising aspects of China’s ADIZ is why they are nearly 50 years late in reciprocating Japan’s ADIZ. China’s new ADIZ, similar to other nationally established ADIZs, requires planes flying through it to take measures to identify themselves to Chinese air controllers, such as filing a flight plan, communicating with Chinese air traffic controllers, or having their transponder turned on [29, 34, 38].

Japan strongly objected to China’s ADIZ because it not only considerably overlapped with Japan’s ADIZ but also covered the Senkaku Islands. Owing to the logic of the sovereignty game, it would have been hard for China not to cover the Senkaku Islands because their exclusion could have been used by Japan to claim that China was not serious about its claim to these islands. In practice, however, China does not appear to have often intercepted Japanese planes flying near the Senkaku Islands. Negotiations in the future between the two countries might be able to set aside their respective ADIZs near the Senkaku Islands, similar to how they set aside national authority for fisheries in that area. However, because Japan’s ADIZ has covered the Senkaku Islands since 1972, it would probably be difficult for Japan to make such a concession.

The large overlap in the two countries’ ADIZ poses risks, because this has led to an increase in the two sides intercepting the military aircraft of the other. Such situations could lead to miscalculation or simply an in-air collision, stoking bilateral tensions, if not a confrontation. Japan’s ADIZ is so expansive that, at one point, it comes within 130 km of China’s coast and covers a considerable portion of China’s uncontested EEZ claim. China’s ADIZ comes even closer to Japan’s Sakishima Islands, especially Yonaguni; however, it essentially only overlaps with portions of Japan’s EEZ that are contested by China (Fig. 4).

Fig. 4

Chinese and Japanese ADIZs and EEZ claims

Furthermore, China’s new ADIZ overlapped with South Korea’s EEZ just southwest of Jeju Island and covered the Ieodo rock. This drew attention to the fact that South Korea’s ADIZ (established by the US military in 1951) did not cover Ieodo, and the only ADIZ that did was Japan’s ADIZ (since 1969). South Korea responded almost immediately to China’s announcement of its ADIZ by holding air and naval exercises around Ieodo. This action was held in defiance of China’s ADIZ, as Seoul did not notify, Beijing about its airplanes flying in this area, although Seoul did provide advance notification to Japan regarding South Korean aircraft flying in the area. Soon thereafter, South Korea responded again by expanding its ADIZ to its south to cover Ieodo and waters to its south (it also expanded a bit to the east and further north into Japan’s ADIZ). This was the first expansion of South Korea’s ADIZ after 1951, and it expanded a total of approximately 104,000 km² in area [29].

Similar to their overlapping EEZ claims, using the TCM to help harmonize overlapping ADIZs, starting with where the three nations’ ADIZs overlap around Ieodo, could be a useful means for ameliorating a potential flash point. Moreover, the TCM could be a useful semi “neutral” venue for China and Japan to considerably reduce their overlapping ADIZs with South Korea potentially acting as a mediator.

Sino–South Korean EEZ Conflict

Ieodo

Socotra Rock, known as Ieodo (이어도) or Parangdo (파랑도, 波浪島) in Korean and Sūyan Jiao (苏岩礁) in Chinese, is approximately 4.6 m under water at its highest point, although it sometimes becomes visible during storms.¹³ China and South Korea both laid claims to this rock; however, South Korea occupied it by building a tower on top of this rock in 2003. The tower supports the Ieodo Ocean Research Station and a helipad. Its location in the northern ECS can be considered strategic because it is 149 km (80 nm) southwest of South Korea’s Marado Island (which is just off the coast of Jeju Island), 287 km, i.e., 155 (NM) east of China’s Sheshan Dao or Yushan Island (near Shanghai), and 287 km (149 NM) west of Japan’s Torishima Island (near Kyushu).

Because Ieodo is an underwater feature, it falls under the jurisdiction of which country’s EEZ it is in, and Ieodo is located within overlapping Chinese and South Korean EEZ claims. Essentially, Ieodo is an EEZ conflict, not a territorial conflict, a point that both China and South Korean spokesmen emphasize. South Korea claims that Ieodo is within its EEZ based on its median line claim and that it is closer to the South Korean coast than China’s coast. China claims Ieodo based on its claim to a continental shelf and specifically to a silt line. The silt line is the limit to which sediments from Chinese rivers blanket the seabed, a standard that would place Ieodo and two-thirds of the joint Japan–South Korea development area inside China’s EEZ [29] (Fig. 5).

Fig. 5

South Korea’s ADIZ before it covered Ieodo. Source: [29]

The Ieodo rock, particularly the South Korean tower on top of it, has been a source of friction between China and South Korea. Chinese CG vessels have regularly patrolled the waters around Ieodo [39, 40]. The destabilizing impact that rapidly advancing maritime technology is having on expectations about the value of maritime space is helping justify those in South Korea and China who wish to press their respective national claims to Ieodo. As two researchers at the Ieodo Research Organization asserted, “Rocks which have been worthless may be worthwhile in the future by advanced science and technology and that they may cause more disputes” [41] (Fig. 6).

Fig. 6

South Korea’s ADIZ after expansion to cover Ieodo. Source: [29]

Sino–South Korea Fisheries Dispute

Compared to Sino–Japanese cooperation on fisheries in the ECS, Sino–South Korea cooperation in fisheries, which is based on a requirement to manage their as-yet unresolved EEZ conflict, has been characterized by significant violence and conflict. The 1998 Sino–South Korean Agreement on Fisheries established two TZs and a PWZ between the two countries that is supposed to ensure the cooperative management of these waters until the EEZ border can be determined (Fig. 7). The PMZ is a jointly managed fisheries zone with a more limited sharing of fishing resources in the TZs. The 1998 agreement established a Joint Fisheries Commission and joint surveillance operations to prevent illegal fishing in these zones. Moreover, the agreement included mutual recognition of each other’s fishing and resource rights in their respective EEZs outside of the area of overlapping claims [29].

Fig. 7

The Fisheries PMZ and TZs between China and South Korea. Source: Wikimedia Commons. https://en.wikipedia.org/wiki/Socotra_Rock#/media/File:Socotra_Rock.png

Although the Sino–South Korean agreement is similar to the 1997 Sino–Japanese fishing agreement, implementation has proven to be much more conflictual and even violent. For example, a December 2010 collision between a Chinese fishing boat and a South Korean coast guard (ROK CG) vessel led to the death of two Chinese fishermen. In October 2011, the ROK CG arrested 27 Chinese fishermen for illegal fishing in Korean waters, thus provoking a nationalist reaction from the Chinese media that warned that South Korea should “prepare for the sounds of cannons.” A month later, an ROK CG vessel was harassed by 25 Chinese fishing vessels after it had detained one of their number off Jeju Island [42,43,44].

In December 2011, an onboard fight between Chinese fishermen and ROK CG members resulted in the death of one CG member and injured another after they were stabbed by a Chinese ship captain. Subsequently, a Korean court sentenced the captain to 30 years in jail with one-to-two-year sentences for other members. In 2013, ROK CG seized more than 180 Chinese fishing boats that had been illegally fishing in its waters. In October 2014, a Chinese captain in ROK CG custody was accidentally shot and killed. The CG members claimed this happened while four other Chinese vessels had surrounded their ship, and crew members were using homemade weapons with one attempting to strangle a CG member. In September 2016, three Chinese fishermen died when their ship caught fire after an ROK CG vessel launched flash grenades at them [45,46,47]. Why Sino–South Korean cooperation in fisheries has proven to be much more conflictual, and especially more violent, than Sino–Japanese cooperation in fisheries remains an unanswered question for future research [45,46,47].

The East China Sea and Global Trends at Sea

Maritime disputes are not unique to East Asia. If we examine the phenomena worldwide, disputes exist on every continent, and they are linked to a range of topics.

Global Data on Maritime Disputes

Disagreements over how to delineate maritime space (boundary disputes) concerning territorial waters (12 NM), EEZs (200 NM), or extended continental shelves are abundant (Tables 1 and 2 and Fig. 8). Sovereignty disputes over islands—both uninhabited and inhabited—are particularly volatile and are often linked to historic claims and occupation and the extended maritime zones and related sovereign rights that the islands confer. Moreover, disputes related to the legal status of certain maritime zones, passageways, and access to marine living resources that traverse invisible maritime boundaries are rampant across the world.¹⁴

Table 1 Total number of maritime boundaries as dyads

Table 2 Settled/not settled maritime boundaries as dyads across continents per 2020

Fig. 8

Countries with remaining maritime boundary disputes in 2020. Per 2020, based on a dataset. Altogether, 121 countries and 180 bilateral boundary segments ranging from 1 to 16 boundaries per country

Based on the dataset by Østhagen [48], in certain instances, a dyad (comprising one boundary segment with two countries) may comprise countries from two different continents (e.g., Africa and Europe in the Mediterranean). In such instances, allocations to a specific continent were made on a case-by-case basis.

The data show the global extent of this phenomenon and that it is not confined to one part of the world or a specific group of states. Unsurprisingly, large countries with more access to maritime space have a larger number of maritime boundaries. Large states, like Russia, the USA, Canada, Japan, and China, have long coastlines and several maritime neighbors where disputes need to be settled. Areas such as the Caribbean Sea, the ECS and SCS, and the Mediterranean Sea, where multiple states are clustered together, thus have a large number of maritime boundaries and related disputes. Moreover, countries with overseas colonies or dependencies—such as France, the UK, Spain, and the United States—have multiple maritime boundaries that are settled and unsettled.

Global Settlement Trends

For maritime boundary disputes, states may select multiple pathways for settlement. They may agree on a mutual solution after bilateral negotiations; they may submit the case for adjudication at the International Court for Justice (ICJ) or another international court, such as the International Tribunal for the Law of the Sea; or they may use third-party arbitration, such as the Permanent Court of Arbitration. However, generally, settlement pathways involving international arbitration are unappealing to states if they can be avoided. Owing to uncertainty in the outcome of international adjudication and arbitration, states do not bring cases before courts or tribunals [49]. Moreover, litigation is expensive, and in the maritime domain, the process often requires considerable scientific data, thus making it expensive for states to pursue delimitation as an approach for dispute resolution [50]. The bilateral resolution of a dispute leaves states with the option of a creative resolution that is not confined by the international rules applied by courts and tribunals [51].

Consequently, approximately 95% of maritime boundaries that have been agreed upon between 1950 and 2020 were settled via negotiations outside the realms of arbitration or adjudication, with states free to select the approach they prefer when delineating maritime space. However, studies demonstrate that although states select bilateral negotiations to avoid the limitations of international adjudication and arbitration, they still depend on and mostly adhere to legal principles as set out by international court rulings [52,53,54].

Despite multiple approaches and principles, and although the settlement of outstanding disputes continues, maritime boundary disputes exist on all continents. In 2020, out of 460 possible maritime boundary disputes, only 280 have been settled (Table 1). This means 180 (approximately 39%) outstanding maritime boundary disputes, ranging from active and conflictual to dormant or successfully managed, require resolution.

How Global Trends Impact the East China Sea

If we link the disputes in the ECS with trends observed for maritime disputes, particularly maritime boundary disputes, certain trends impacting boundary-making at sea deserve additional consideration.

The Centrality of the Law of the Sea

First, it is important to recognize that disputes discussed here are completely or partially related to LOS and the rights that were subsequently conferred on states. The expansion from the 12 NM territorial zone to the 200 NM EEZ ensured that all states (apart from those that are landlocked) acquired new rights and opportunities (Bailey, 1997). As reported by Keohane and Nye: “Just as medieval villages were eventually fenced off in response to economic change, states in the 1970s “fenced off” larger parts of oceans as technological and economic change increased the uses of the oceans” [55]. Maritime space up to 200 NM (and in the case of the shelf, even further) previously dismissed as uninteresting suddenly became an entitlement requiring protection. UNCLOS provided international legitimacy for considerable expansion in the jurisdiction of maritime states.

Although states engage in disputes—sometimes even using blunt force—to have their way at sea, they generally operate within the boundaries of the international legal regime that awarded them these new rights. The engagement in disputes that might challenge aspects of specific UNCLOS principles might prove to be a poor long-term strategy for any coastal state that benefits from these principles. Coastal states became eager to uphold and defend that regime.¹⁵ Therefore, Baker [56] argues that, as on land, states are behaviorally conditioned by an international norm against the “forceful acquisition of maritime spaces and resources of other states.” States have ensured a “lock-in” of their sovereign rights at sea, while technological developments and resource demands continue to prompt considerable functional use of maritime space.

Increased Functional Value

It may be tempting to equate the value and importance of maritime space (and subsequent disputes) to the functional value of that space. In a 2016 study of 417 outcomes of boundary negotiations, Ásgeirsdóttir and Steinwand [57] argued that states settle maritime boundary disputes to provide legal certainty to ensure the potential development of oil and gas resources. The same results are confirmed across case studies in areas ranging from the Arctic Ocean to the Bay of Bengal [58,59,60].

Furthermore, the function of ocean space itself has expanded, with additional resources being harvested at sea, ranging from fisheries to hydrocarbons. Multiple trends are fueling this expansion; a considerable amount of gas that is expected to replace oil consumption is present in offshore reservoirs [61] while offshore wind farms are increasingly becoming a source of global investment [62]. Seabed minerals are attracting considerable interest [43, 63]. Using ship-based extraction technology, Japan successfully mined metals from its seabed in 2017 and expects large-scale commercialization of multiple offshore deposits in the near future [42, 64].¹⁶ In 2023, Norway became the first country in the world to open up for commercial licensing on its seabed. Straddling (and high seas) fish stocks constitute a shared resource;¹⁷ however, as Wood et al. [65] emphasize, global fish stocks are decreasing owing to overfishing in both international waters and within EEZs. Furthermore, the debate on how to govern and utilize marine genetic resources is increasingly pertinent and linked to the ongoing Marine Biodiversity of Areas Beyond National Jurisdiction negotiations [66,67,68].

One could assume that the settlement of outstanding maritime boundaries (as almost half of all remain in dispute) would become an easier process as the functional value of the disputed space is increasing but further nuance is necessary. There is an alternative argument that offshore resources make a disputed area more valuable and thus expensive to give up, because almost any maritime boundary resolution involves compromise. Frequently, this is invoked when scholars and media highlight the potential for “geopolitical conflict” in maritime areas with resource abundance, e.g., the Arctic Ocean [69], the SCS [70], or the Caspian Basin [71, 72].

Security Concerns

Functional value (e.g., oil and gas resources) undoubtedly plays an important role as a motivating factor. However, this value must be seen along with security relations between negotiating actors. It is obvious to assume that the worse the relations, the more difficult an agreement would be. Ásgeirsdóttir [73] demonstrated that for US maritime boundaries, a negative security relationship can act as a trigger for settlement. Moreover, this has been shown by Moe et al. [60] in the 2010 agreement between Norway and Russia in the Barents Sea [74].

Arguably, there is a “tipping point” here. Initially, similar to the cases of China–Japan and China–South Korea, disputes and security concerns related to fisheries initially led to cooperation agreements to manage these issues (in 1997 and 1998, respectively). The security concerns and “negative” interactions between states over sovereign rights at sea were a reason for these agreements on how to manage maritime space, although they were not complete maritime boundary agreements. However, at some point, relations become so hostile that any form of agreement is seen as a tacit concession.

Symbolism at Sea

What drives dispute dynamics between states over this tipping point is that not only does the dispute concern the functional use of the maritime domain in question, but it also concerns the interest and engagement of domestic actors and how ocean politics is increasingly entangled in national politics. Vasquez and Valeriano [75] described a conflict as spiraling when it becomes infused with symbolic qualities. It might be assumed that maritime disputes—whether concerned with fishing rights or boundaries—would be a simple matter of delineating rights and ownership because of the tangible character of such disputes.

However, the Senkaku/Diaoyutai/Diaoyu islands dispute is a prime example of how the role of maritime space has changed in domestic politics over the course of four decades from a functional space that often inspired limited engagement to a national space requiring “protection” and defense [56, 76,77,78,79]. These trends indicate that when a maritime dispute reaches the political agenda, there are domestic actors who stand to benefit from infusing it with intangible dimensions, such as “national pride” or “being cheated out of what is ours” [80, 81]. Opposition to concessions in the maritime domain takes the form of lobbying by powerful nationalists or groups having economic interest, loss of the popular vote or confidence, or strong media opposition [74]. If concessions are made in negotiations (inherent to any maritime boundary delimitation) and are not perceived to be domestically acceptable, settling the dispute will prove to be challenging, even if leaders and foreign policy elites have reached an agreement via bilateral negotiations.

This is not unique to countries surrounding the ECS; for example, maritime disputes were a prominent part of the campaign to leave the EU during the Brexit referendum in the UK in 2016, despite fisheries only accounting for 0.05% of the country’s GDP [44, 82]. In bilateral Norwegian–Russian negotiations over fisheries around Svalbard from the 1990s onwards, the domestic audience has played a central role [83]. In the 2018 Colombian presidential elections, the maritime boundary disputes between Nicaragua and Colombia over the San Andrés Archipelago (and the 2012 ICJ ruling) were used by candidates to stir up popular support [84, 85].

Thus, maritime disputes are not devoid of intangible and symbolic elements that can lead to conflicts escalating beyond the initial dispute. These concerns are not only the economic interests of the actors involved but also wider ideas of symbolism and identity. States (and their inhabitants) do care about their maritime disputes, even those of limited economic value, and increasingly so. Once a dispute has become politicized, any resolution of the dispute has a domestic political risk. Kleinsteiber [86] argues that “The fundamental drivers behind the disputes in ECS and SCS are not potential or claimed natural resources but rather domestic politics, rising nationalism, and irredentism.” Indeed, even undertaking negotiations may be risky.

The Sinocentric Tributary System

An additional complication in the disputes in the ECS is the sudden and in some instances violent transition in the mid-nineteenth century from the Sinocentric tributary system governing inter-state relations around the ECS to the Westphalian system. This is a process that involved predatory behavior by Western powers and in later decades by Japan. The legacy of this transition has impacted the contemporary dispute in two ways.

First, states in this system did not engage in acts that would be recognizable under LOS or Western international law, including pre-twentieth century law, to make territorial claims to uninhabited islands between them or to claim fishing rights. The claimants in territorial disputes in the ECS and SCS have been searching for artifacts from the era of the Sinocentric system to stake claims to territory and fishing rights under LOS and contemporary Western international law. This is distinct from using historical artifacts, from say pre-modern Europe, to make contemporary sovereignty claims under LOS, and is problematic as it involves projecting behavior and motivation onto actors who were operating under an incommensurate system and different understandings of international relations that prevailed in East Asia before the arrival of the Westphalian system.

Second, international law in general has a legitimacy deficit in East Asia because of the way it was imposed, often by force, by Western imperial powers in the nineteenth century. This is arguably why East Asian and, more generally, Asian nations have by far the lowest rates of compulsory jurisdiction by the ICJ and International Criminal Court; moreover, they have a low participation rate in international conventions [10]. This legitimacy deficit is especially acute for China, which makes it less likely to abide by LOS and has based maritime claims on the pre-Westphalian practice of the Sinocentric tributary system. This is particularly visible in China’s nine-dash line in the SCS.¹⁸

While it is easy to see China’s questioning of LOS as purely out of self-interest, it appears to be based on genuine perceptions and China’s history of subjugation by Western imperial powers. Moreover, Taiwan has questioned the relevance of UNCLOS in the SCS, citing their older and historical claims, which are also the basis for the PRC’s claims in the SCS. Other actors, most notably Japan, have in the past questioned the legitimacy of Western international law, particularly in the 1930s and 1940s, when Japan often equated Western international law with unequal treaties imposed on East Asian countries by imperial powers [87].

Finally, a legitimacy deficit, or at least differences in understanding LOS, can create differences between East Asian countries and Western countries. For example, by the first decade of the twenty-first century, if not earlier, a de facto regional consensus had become evident, one spearheaded by China but implicitly shared even by the US allies Japan and South Korea that foreign military activities, including exercises, surveys, and intelligence gathering, in another country’s EEZ were illegitimate [88].

The legacy of the Sinocentric Tributary system and, generally, the legitimacy deficit for Western international law, including LOS, pose an additional complication for maritime disputes in the ECS and SCS, a factor that does not appear to exist in Europe or North America but might exist in other regions that were impacted by the Westphalian international state system in the nineteenth century. One concrete manifestation of this deficit is that it makes parties to maritime disputes even more reluctant than is the case globally to bring these disputes to international arbitration. Moreover, when one party insists on international arbitration, as did the Philippines in the SCS, the other party may be more likely to reject the legitimacy of arbitration, which is what China did. Bilateral settlement makes it easier for parties to bring pre-Westphalian practices and history into settlement negotiations.

Superpower China

A final factor that arguably makes the ECS and perhaps the SCS maritime disputes distinct from those in other regions is China’s status as an emerging power that not only has historical reasons to doubt the legitimacy of Western international law but also has less stake in upholding LOS because it may believe it has more unilateral options for imposing its preferred solutions on these conflicts than the other weaker parties. Moreover, as an emerging superpower, China may even hold the ambition to transition from being a rule-taker to a rule-maker, thus seeking to remake international law and institutions, including LOS, to reflect its national interests, generally similar to how emerging great powers have previously performed [89].

Conclusion

Because of the complexity of maritime disputes (and their negotiations), it is difficult to identify simple causal mechanisms that explain why states settle disputes. The specific legal characteristics of the boundary dispute in question (i.e., its origin, which veto players exist, and how the position of each country stands vis-à-vis cotemporary international court rulings) set the parameters of boundary disputes unique to that case [90]. Countries are sensitive to changes in international jurisprudence and view their boundary disputes as an interlinked collection rather than single-issue cases [91,92,93]. In fact, to truly grasp nuances in the position of China, Japan, Taiwan, and South Korea concerning these boundary and territorial disputes, an examination of their collection of disputes is important.

In this article, we have analyzed the Sino-Japanese dispute over the Senkaku (Diaoyu) islands, Taiwan’s role in this dispute, the Sino-Japanese disputes over their EEZ and ADIZ borders, and the Sino-South Korean dispute over Socotra rock and their EEZ border, especially as it relates to fishing.

These ECS disputes demonstrate how disputes over maritime space can acquire additional importance when they become linked to domestic politics, national identity, and perceptions of history. Moreover, because states enhance their naval and maritime policing capabilities along with technological progress, their capacities for monitoring and controlling their maritime zones have expanded. To a greater extent than before, events at sea trigger immediate response and attention from political leaders and national public opinion.

We see this trend in the ECS. In particular, similar to global conflict patterns, as soon as territory is included, the dispute is more likely to escalate and/or become protracted [94]. The Senkaku/Diaoyutai/Diaoyu islands dispute illustrates this trend. However, even the subsea surface rock of Ieodo has been “territorialized” in Chinese and South Korean domestic politics and thereby has attracted more attention and is used more actively in domestic politics in China, South Korea. Even EEZ disputes have become increasingly “territorialized” for public opinion. Technological advances have increasingly allowed the public to “see” maritime spaces, including the seabed, thus making it easier for them to identify these maritime spaces with the nation.

On the one hand, we have the idea of the ocean and states’ ocean space as a legalized, institutionalized, and governed domain in which states tend to abide by the rules set forth by UNCLOS because it is in their common interest to do so. On the other hand, greater domestic engagement is spurred by the recognition of the ocean as a policy issue requiring common efforts to combat everything from a rise in sea level to plastic pollution.

Maritime boundary disputes that have appeared on agendas more recently (in the past two decades) have involved a wider range of relevant factors and foster broader public engagement than maritime disputes in the 1970s and 1980s. “A boundary itself is just one element. More important are those normative factors increasingly related, such as military interests, economy, historical memory, and larger security considerations” [92]. Greater utilization of oceans or national maritime zones as an issue in domestic politics is a rising trend, as ocean space continues to rise on the agenda. This trend is apparent in the ECS and in global ocean politics writ large.