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Definition of “international strait” presents dilemma for Japan in its response to Chinese ship intrusions

By Imano Yuki


In July 2022, a Chinese navy vessel intruded into Japan’s territorial waters in the Tokara Strait, located southwest of Yakushima Island in Kagoshima Prefecture. China claims that the Tokara Strait is an international strait, which means foreign ships are permitted to sail through it relatively freely. China appears to be attempting to establish the fact [that the Tokara is an international strait] by accumulating a track record of navigating the strait. The Japanese government has only expressed its concerns to China and has not taken stronger action. It seems that Japan as a nation of peace has certain reasons behind its approach.


The Chinese Navy’s Shupang-class survey ship intruded into Japan’s territorial waters, passing through the Tokara Strait between Yakushima and Kuchinoshima, which is southwest of Yakushima. The ship took three hours to sail from the Pacific Ocean to the East China Sea from around 8:00 p.m. on July 20.


The Japanese government dispatched a Maritime Self-Defense Force supply ship and patrol aircraft to monitor the Chinese ship. The government conveyed its concerns to China through diplomatic channels but did not lodge a “protest,” which is a stronger diplomatic action.


A Chinese naval vessel first entered the Tokara Strait in June 2016. China took the opportunity to claim that the Tokara Strait is an international strait that is frequently used for shipping and other purposes. Although there were no intrusions for a while after 2016, a second and third intrusion occurred in November 2021 and April 2022, respectively. The frequency of the intrusions has increased in recent years. At Japan-China bilateral working-level meetings, China has repeatedly stated that the “Tokara Strait is an international strait.”


Chinese warships can pass freely through the Tokara Strait according to certain rules under the United Nations Convention on the Law of the Sea regardless of whether it is an international strait. In normal territorial waters, submarines must be surfaced during passage, making their operations completely visible. Submarines navigating an international strait are allowed to remain submerged while passing through, meaning they can be stealthy, the most important characteristic of a submarine.


The Tokara Strait is one of the shortest routes connecting the Pacific Ocean with Ningbo in Zhejiang Province, which is home to a Chinese naval base. The passage of Chinese submarines while submerged will enable China to covertly intercept U.S. aircraft carriers approaching from the Pacific in the event of a Taiwan contingency.


Japan is reluctant to stand up and argue that the Tokara Strait is not an international strait. Japan avoids the issue as much as possible, simply taking the position that “there are no international straits in its territorial waters.”


Impact of the Three Non-Nuclear Principles


There are five straits which are internationally recognized as international straits in the waters around Japan: Soya, Tsugaru, Osumi, Tsushima Strait East Channel, and Tsushima Strait West Channel. Japan uses its own criteria based on its Territorial Sea Law to designate these five straits as “specific sea areas.” Japan limits territorial waters within the five straits to three nautical miles from its baseline, which is narrower than the 12 nautical miles recognized by the United Nations Convention on the Law of the Sea. Japan thereby intentionally creates open seas in the center of these straits. This allows foreign ships to freely sail through the straits in the same way as international straits.


Why did Japan create such open seas in its straits?  One government official explained that, “The position is in line with the Three Non-Nuclear Principles,” although the government has not officially acknowledged this position. U.S. ships carrying nuclear weapons cannot enter Japan’s territorial waters. Limiting U.S. naval activities may impede the function of the “nuclear umbrella,” which the U.S. provides to Japan. By minimizing territorial waters in its straits, the Japanese government allows for open seas through which U.S. warships can pass.


If Japan were to become involved in the international strait dispute initiated by China, people may focus on the treatment of the five straits and the actual state of the Three Non-Nuclear Principles, which up till now have remained ambiguous. China may have seen through Japan’s situation and taken advantage of the international straits issue.


The ruling parties are starting to object to the Japanese government’s cautious stance. At a July 29 Liberal Democratic Party (LDP) meeting to discuss intrusions into territorial waters, LDP foreign affairs division chair Sato Masahisa called out China by name and said, “This is a case of intrusion into territorial waters which involves legal warfare.” Sato told reporters after the meeting that China’s “allegation that [the Tokara Strait] is an international strait is highly malicious,” and he urged the government to take a stronger stance, such as making a protest.

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