The Senkaku/Diaoyu islands dispute: unpacking tensions in the East China Sea

The Senkaku/Diaoyu Islands dispute intensifies, pitting Japan, China, and the U.S. against each other. Historical claims and legal complexities fuel escalating tensions in the East China Sea.

The dispute over the Senkaku Islands, administered by Japan and claimed by China as Diaoyu Dao, as well as by Taiwan (ROC) as Diaoyutai Lieyu, remains a prolonged and intricate issue. China, notably through its Coast Guard and naval assets, challenges Japan’s control over the islands. Despite the ongoing dispute, a diplomatic stalemate persists, with neither side escalating to open conflict.

Post-Cold War dynamics have seen competitive efforts over island control. The analysis delves into aspects like territorial sovereignty, maritime rights, international law, and the role of the United States. China seeks U.S. neutrality, while Japan aims for U.S. commitment to island defence through their alliance, capitalizing on the growing Sino-U.S. rivalry.

Japan, not relying solely on U.S. support, has concurrently bolstered its maritime capabilities to counter assertive Chinese actions. The broader geopolitical implications highlight the strategic interests at play in the Asia-Pacific region.


Sino-Japanese relations have been significantly strained by a range of bilateral disputes, encompassing historical interpretations and national stances on maritime and territorial issues. Among these conflicts, the dispute over the sovereignty of the Senkaku Islands has emerged as a focal point, escalating geopolitical tensions in the East China Sea (ECS) over the past few decades.

Japan presently administers these uninhabited islands, consisting of five islets – Uotsuri, Kuba, Taisho, Kitakojima, and Minamikojima – along with three rocks – Tobise, Okinokitaiwa, and Okinominamiiwa. Situated 190 nautical miles southwest of Okinawa’s coast, the Senkaku/Diaoyu islands are near China’s east coast (200 nautical miles) and Taiwan’s northwest coast (120 nautical miles).

This geographical proximity intensifies the strategic significance of the dispute, contributing to the complex and sensitive nature of the ongoing tensions in the region (Hamakawa 2007; Pedrozo 2016).

The Senkaku Islands, strategically located on crucial sea lines of communication in the East China Sea (ECS), became a focal point of intense Sino-Japanese maritime conflict in the late 1960s. The escalation was triggered by surveys conducted by the United Nations Economic Commission for Asia and the Far East, which suggested the presence of substantial oil and hydrocarbon reserves around the islands (Chansoria 2018).

In response, in 1970–1971, the People’s Republic of China (PRC) asserted that the Diaoyu (Senkaku) Islands have historical ties to Taiwan, a territory also claimed by China, thereby considering the islands as sovereign Chinese territory. Japan countered by citing legal assertions grounded in international law, claiming de facto control over the Senkaku Islands since 1895 without any prior complaints from China.

The official position of the PRC contends that ‘Diaoyu Dao is China’s inherent territory in all historical, geographical, and legal terms,’ drawing on historical evidence of the islands being administered as part of Taiwan since the Ming and Qing dynasties (MOFA of PRC 2012).

Chinese historical claims rest on three main categories: the historical use and naming of the islands by China, the jurisdiction of the islands during the Ming dynasty, and maps from that era depicting the islands as Chinese territory.

This historical backdrop forms the basis of the ongoing territorial dispute, reflecting the contrasting narratives and interpretations presented by both China and Japan regarding the sovereignty of the Senkaku Islands.

To substantiate its territorial claims over the Senkaku Islands, Beijing relies on historical records from the Ming and Qing dynasties. For instance, it points to Chen Kan’s 1534 record of Chinese envoys to Ryukyu, which mentions the route passing by ‘Diaoyu Dao, Huangmao Yu, Chi Yu’ and designates Diaoyu Dao and Chiwei Yu as Chinese territories.

Chinese maps, like Hu Zongxian’s 1561 “An Illustrated Compendium on Maritime Security,” illustrate the Diaoyu Islands and claim the Ming dynasty’s coastal defence measures in response to Japanese pirate threats, including the Diaoyu Islands. The Qing court, according to the PRC, placed the Diaoyu Islands under Taiwanese jurisdiction.

Foreign maps, including those by Japanese, French, and British sources, are also cited by China to emphasize historical connections, as they coloured the Diaoyu Islands the same as Taiwan. In essence, Beijing argues that historical documents and maps support its longstanding assertion of sovereignty over the Senkaku Islands, reinforcing its territorial claims based on centuries-old records and foreign cartography.

Japan has not contested the historical Chinese naming of the islands over the centuries, but it has relied on international law to challenge China’s territorial claims. According to Japan, the mere discovery of an island or its geographical proximity does not establish sufficient conditions for asserting territorial sovereignty, as outlined by the Okinawa Peace Assistance Center in 2016.

Japan has specifically questioned the validity of historical maps, such as Hayashi Shihei’s 1785 Illustrated Outline of the Three Countries, arguing that inaccuracies, like Taiwan being depicted as smaller than Okinawa, undermine their credibility.

Tokyo argues that these maps lack explicit evidence connecting the Senkaku Islands to the Ming or Qing dynasties of China. Japan contends that the mere presence of the islands on historical maps does not automatically designate them as Chinese territory. The Japanese Ministry of Foreign Affairs (MOFA) asserted in 2014 that historical maps from that era do not explicitly state the affiliation of the Senkaku Islands with China.

In a 2012 speech, then-Japanese Prime Minister Yoshihiko Noda emphasized Japan’s stance, declaring that the Senkaku Islands are “clearly an inherent territory of Japan, in light of historical facts and based upon international law.” Japan maintains that there is no “issue of territorial sovereignty to be resolved” concerning the Senkaku Islands, as stated by MOFA in 2016. This position underscores Japan’s reliance on historical facts and international legal principles to assert its sovereignty over the disputed islands.

The Japanese Government, following the incorporation of the Ryukyu Islands into Okinawa Prefecture, included the Senkaku Islands within the same prefecture based on surveys conducted in 1885. These surveys carried out by established methods for acquiring territorial sovereignty under international law, identified the islands as terra nullius, signifying that they were uninhabited with no indication of being under the control of any state (MOFA of Japan 2014).

Japan supports its claims by presenting historical documents, including a 1953 issue of China’s People’s Daily (Renmin Ribao), which reported on the inhabitants of the Ryukyu Islands, including the Senkaku/Diaoyu Islands, resisting the U.S. occupation (People’s Daily 1953). Japan argues that this indicates the People’s Republic of China (PRC) recognized the Senkaku Islands as part of Japanese territory in the 1950s and 1960s.

Additionally, Japan points to Beijing’s lack of objections to the United States using the Senkaku Islands for firing drills and a Chinese map publisher’s 1958 atlas illustrating the islands as the ‘Senkaku Group of Islands’ under Okinawa (MOFA of Japan 2010; Okinawa Peace Assistance Center 2016; Sakamoto 2016). These instances are cited as evidence of historical acknowledgement and acceptance of Japanese sovereignty over the Senkaku Islands by the PRC.

From an international law and mutual agreements perspective, China asserts that it was unfairly coerced into ceding territories, including the Diaoyu Islands, under the 1895 Treaty of Shimonoseki. According to China, Japan renounced all claims over these territories, including the Diaoyu Islands, through the 1952 Sino-Japanese Peace Treaty.

Japan, however, argues that the treaty lacks evidence regarding the inclusion of the Senkaku Islands in the ceded territories, emphasizing that Japan’s decision to incorporate the islands into Okinawa Prefecture predates the signing of the Treaty of Shimonoseki in January 1895. Japan also relies on the 1951 San Francisco Peace Treaty, which does not address sovereignty over the Senkaku Islands.

The Treaty of San Francisco, however, placed the Senkaku Islands under U.S. administration until the 1971 Agreement Between Japan and the United States of America. China, asserting sovereignty after the discovery of petrochemical reserves in 1971, deems the 1971 treaty illegal. The U.S. intelligence report of the time suggests a strong Japanese claim to sovereignty over the Senkakus.

The ownership of the main island, held privately and inactive, allowed both governments to maintain a low profile on the issue. After leasing and eventual nationalization by Japan in 2012, tensions escalated, triggering violent protests in China. Ship incursions into the territorial and contiguous waters increased significantly since then, with a notable rise in the Chinese presence since 2020. This marked the end of the tacit bilateral management of the dispute, leading to heightened tensions and increased maritime activities around the Senkaku Islands.


China and Japan have yet to establish a maritime boundary across the East China Sea, leading to a complex legal situation concerning the Senkaku Islands. These islands lie within the overlapping zone of China’s extended continental shelf claim and Japan’s exclusive economic zone (EEZ) claim. According to Article 121 (3) of the 1982 UN Convention on the Law of the Sea (UNCLOS), “Rocks which cannot sustain human habitation or economic life of their own” cannot have an EEZ or a continental shelf.

Japan contends that the Senkaku Islands are more than just rocks and therefore generate an EEZ and continental shelf, but China has not officially clarified its position on this matter.

Japan defines its EEZ boundary west of the southern islands of Kyushu and Ryukyu, not using the Senkaku Islands as the baseline. On the other hand, China establishes its maritime boundary along the natural extension of its continental shelf. UNCLOS Article 57 specifies that an EEZ boundary may extend up to 200 nautical miles from the baseline or to the median line in case of overlapping claims.

Article 76 defines the extended continental shelf, which can reach up to 350 nautical miles from the baseline or the continental shelf’s end, whichever is less. Japan identifies the median line as the maritime boundary, while China sees the limitation of the extended continental shelf as the boundary. This results in an overlap of approximately 81,000 square miles in the East China Sea, covering the Senkaku/Diaoyu Islands. The issue has become politically contentious since the 1990s.


The maritime dispute between China and Japan in the East China Sea has centred around gas fields along the continental shelf, resulting in heightened tensions. China, installing gas rigs outside Japan’s claimed median line but within its extended continental shelf boundary, has prompted Japan’s concerns over potential resource extraction in contested areas.

In 2004, Japan requested China to share geological survey data to address fears of gas field expansion across the median line, leading to a tense encounter in 2005. Joint exploration proposals were made in 2008, but Japan rejected them initially, agreeing only after a summit meeting later that year, which included one field on the Japanese side for joint exploration.

Despite this, disputes persisted, with China unilaterally developing the Tianwaitian/Kashi gas field and cancelling joint exploration negotiations in 2010 after a confrontation near the Senkaku/Diaoyu islands. In 2013, the Air Defence Identification Zone (ADIZ) established by China over most of the East China Sea escalated tensions. Japan protested, and the U.S. affirmed the applicability of Article 5 of the U.S.-Japan Mutual Defense Treaty to the Senkaku Islands.

China continued exploration platform placements near Japan’s proposed median line, leading to protests from Japan. Despite increased defence budgets and discussions on collective self-defence, China and Japan have agreed not to enforce their respective fishery rules in overlapping maritime claims. While lawfare continues near the Senkaku Islands, the two nations have generally adhered to this agreement in the broader East China Sea.


The Senkaku/Diaoyu Islands dispute is not merely a historical and legal matter but is intricately connected to the geopolitical strategies of Japan, China, and the United States. The three nations have adopted divergent approaches to the issue, with Japan seeking explicit U.S. support for its sovereignty claim. However, the U.S. has refrained from explicitly endorsing Japan’s claim, emphasizing acknowledgement of Japan’s administrative control without confirming the application of the defence treaty to the islands.

Tensions have heightened with both China and Japan asserting sovereignty, engaging in regularized and explicit demonstrations of control. The Chinese Coast Guard’s activities, while non-combative, present a potential for conflict escalation, especially with the new Chinese Coast Guard Law allowing the use of force. Chinese military vessels and submarines have also operated in the contiguous waters around the islands, contributing to rising tensions.

The U.S. remains concerned about the dispute’s implications, considering its obligations under the 1960 U.S.-Japan Treaty of Mutual Cooperation and Security. Japan recognizes the need to take primary responsibility for defending the Senkaku Islands, particularly in scenarios like a grey-zone attack by disguised and armed Chinese fishermen.

In February 2021, China enacted the China Coast Guard Law, granting authorization to use weapons, adding complexity to the situation. The legal ambiguity surrounding warships’ rights in territorial waters further complicates assessments of China’s actions. With tensions unabated and no resolution efforts in sight, Japan may need to bolster its defensive capabilities.

The East China Sea tensions parallel those in the South China Sea, reflecting the broader U.S.-China geopolitical rivalry. Japan’s engagement in maritime security assistance to Southeast Asian countries, such as the Philippines and Vietnam, aligns with the changing dynamics in the South China Sea, offering an alternative dependence option for these nations amid the rising geopolitical tensions.


In the post-Cold War era, the previously ambiguous territorial and maritime disputes involving Japan, China, and the United States are unravelling, leading to heightened tensions, especially since Japan’s nationalization of the Senkaku Islands. Despite the uninhabited history of the islands, the Chinese and Japanese narratives diverge, with China relying on dynastic records and Japan emphasizing contemporary international law.

While Japan aligns its claim with the rules-based order advocated by the United States and its Quad partners, China employs a combination of maritime force buildup and lawfare, finding limited support in international law for sovereignty and maritime demarcation over the islands.

Japan’s concern about potential abandonment by the United States in the face of a Chinese occupation of the Senkaku Islands has been somewhat alleviated by reassuring comments from U.S. officials. However, Japan’s own naval and Coast Guard strengthening is crucial for deterrence against China and ensuring a robust U.S. commitment to the alliance.

The perceived threat from China to the Senkaku Islands, rather than the broader U.S. request for burden-sharing, becomes the primary reason for the Japanese public to support an increase in the defence budget.