Governed by Japan and known as the Senkaku Islands in the country, but the Diaoyu Islands in China, and then the Diaoyutai Islands in Taiwan, this small group of uninhabited rocks have become a geopolitical flashpoint in the Indo-Pacific region.

Japan has claimed the islands since the end of the Sino-Japanese War in 1895. However, as Taiwan and China also lay claim to their sovereignty, they have been a continued source of tension.

After Japan formally claimed the islands in the late 19th century, after discovering them as terra nullius (‘nobody’s land’) in 1894, the area remained under Japanese control. However, after the Second World War, they were then governed by the US. This administration ceased in 1972 when the islands were bought by a Japanese entrepreneur, Hiroyuki Kurihara.

The Kurihara family had been leasing three of the five disputed islets to the Japanese government, an arrangement which ended in 2012 when the government bought the Senkaku Islands outright for Y205bn ($14.5m). The deal, according to Japan’s Chief Cabinet Secretary, Osamu Fujimura, would “maintain the Senkaku’s peace and stability“. However, China’s reaction to the move did little to assure the islands of either.

Oil and gas potential in East China Sea piques China and Taiwan interest

It wasn’t until the 1970s that China and Taiwan began questioning sovereignty of the islands, with many believing the newfound interest was linked to the discovery of potential oil reserves. In late 1968, the UN conducted a survey that indicated the possibility of petroleum resources in the East China Sea, specifically around the Senkaku Islands. It claimed that the “continental shelf between Taiwan and Japan could contain one of the most high-volume oil and gas reservoirs in the world, to the extent of being close to the size of the Persian Gulf reservoirs”.

The findings were confirmed the following year by Chinese authorities, and this shortly after China began to push forward its claims of sovereignty over the area. By 1971, China was making public claims over the Senkaku Islands citing, with little proof, ‘historical ties’ to the area. The claims remain widely disputed by historians due, primarily, to a lack of documented records supporting them.

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Nonetheless, Chinese authorities have continued to claim ownership of the islands, telling Beijing-based official state news agency Xinhua in 2012 that “Diaoyu [Senkaku] and its affiliated islands have been considered part of China since ancient times. Chinese people were the first to discover, name and administer these islands.”

Japan was quick to point out that China’s enthusiasm for the islands only seemed to emerge when the potential oil reserves were revealed, with the Ministry of Foreign Affairs of Japan stating: “Until then, they [China and Taiwan] had never expressed any objections” concerning Japanese administration of the islands.”

Tensions flare as China pushes boundaries

Following Japan’s purchase of three of the disputed islets in 2012, tensions between it and China (who had rarely been on the best of terms) escalated once again. China initially retaliated with minor protests outside the Japanese embassy in Beijing, followed by more physical acts of a defiance.

The country began regularly entering the Japanese controlled waters around the islands in violation of its territorial sovereignty and, in late 2013, announced it would establish the East China Sea Air Defence Identification Zone. The zone, which according to Chinese officials aimed to help Beijing “guard against potential air threats”, covers a large body of water, including the disputed territories, and this only heightened tensions between the two countries.

Over the next six years, Chinese vessels frequently entered the zone around the Senkaku Islands. Japanese authorities recorded Chinese ships entering its controlled waters 819 times in 2013, a number that increased to 1097 by 2019.

In July 2020, Japan addressed the issue when it released its defence white paper stating that China has “relentlessly continued attempts to unilaterally change the status quo by coercion in the sea area around the Senkaku Islands” adding that “Japan cannot accept China’s actions to escalate the situation”.

Japan receives US support over East China Sea and Senkaku Islands

From 1996 onwards, US authorities have sporadically weighed in on the Senkaku Islands conflict. However, it wasn’t until 2014 that Japan received the clear support it had been waiting for. During a four-day trip to Asia, then-president Barack Obama confirmed that the US would strongly oppose any attempt to threaten Japanese sovereignty. He explained that: “The policy of the US is clear – the Senkaku Islands are administered by Japan and therefore fall within the scope of Article 5 of the US-Japan Treaty of Mutual Cooperation and Security. And we oppose any unilateral attempts to undermine Japan’s administration of these islands.”

The Chinese Foreign Ministry reacted by saying: “The US should respect facts, take a responsible attitude, remain committed to not taking sides on territory and sovereignty issues, speak and act cautiously and earnestly play a constructive role in regional peace and stability.” It is unknown which stance the Chinese authorities would have taken had the US backed their claims over the island…

Support from the US for Japan’s claims was strengthened under President Joe Biden, with US and Japanese forces conducting a joint military exercise involving more than 9,000 service members in late 2021. The exercises, known as Keen Sword 21, were carried out to train both camps on how to defend Japan, Senkaku Islands included, in the face of attack. The show of strength, likely for China’s benefit, may also have been part of US attempts to discourage China from any further attempts to claim sovereignty over land in the area.

China, however, is not only the world’s most populous country, it also has the world’s largest army by active military personnel, with 2.2 million troops, compared with 1.4 million in the US and only 247,000 in Japan. These imposing statistics are bound to weigh heavily in the heads of Japanese and US authorities should further conflict arise. Should China ever gain control of the islands, their geographical position would enable the Chinese navy free access to the Pacific, an exceptional military benefit all opposing parties would be keen to avoid.

Is either side likely to go to war over the Senkaku Islands?

The Senkaku Islands are the heart of the East China Sea dispute. Alongside significant oil reserves, they offer strategic shipping routes for the transport of goods and, perhaps more importantly, military passage. Japan maintains they are an "inherent part of the territory of Japan" and refutes claims its sovereignty should be called into question, adding there "exists no issue of territorial sovereignty to be resolved".

Japan’s position remains clear: it owns the islands, will continue to do so, and will make no attempt to negotiate. China, on the other hand, is continuing to challenge Japan’s authority, and increasing its efforts to gain control of the islands. It is sending more advanced vessels into the Japanese-controlled waters on a frequent basis, thus heightening tensions further. Japan can rely on the US, to a certain extent, although there are additional elements to consider.

Should Japan refuse any form of cooperation over the sovereignty of the islands, it risks pulling the US into a battle where the stakes would be unknown, while also ending economic relations with its largest trade partner in China. However, should it enter negotiations to reach a middle ground, both internationally and domestically this could seen as a sign of weakness, politically damaging at home and leaving Japan open to further incursions on its territory more widely.

It may seem unlikely that two economic superpowers will risk so much over the sovereignty of a few small islands, but as Vladimir Putin's actions in Ukraine in 2014 and 2022 have shown, peace cannot be taken for granted anywhere in the world, particularly when historical disputes over territory are concerned. Few outside of China and Japan may have heard of the Senkaku Islands in 2022, and it is to be hoped that that stays the case.