China Defends Warship Maneuver Through Japan’s Territorial Waters

China said on Monday that its naval ship conducted a “lawful and legitimate” transit in Japan’s territorial waters last week, exercising its right under an international treaty on maritime law.

The Hai Yang 25, a Chinese hydrographic survey ship, entered Japan’s southwestern territorial waters in the Osumi archipelago from 6 a.m. to 7:53 a.m. on Saturday, according to the defense ministry in Japan. The ship is used to conduct research on underwater topography for submarine navigation.

“The Tokara Strait can be sured for international navigation, and by sailing through the strait, the Chinese vessel was exercising its right of transit passage, which is fully lawful and legitimate,” said Mao Ning, spokesperson for China’s Foreign Ministry, during a press conference on Monday.

The less than 35-mile-wide waterway lies between the island of Yakushima to the north and the island of Kuchinoshima to the south, while connecting the East China Sea, where Japan and China have a maritime dispute, to the west and the Philippine Sea and the Pacific Ocean to the east.

The strait forms the so-called first island chain, that extends southward from Japan to Taiwan and the Philippines. The first island chain is part of a containment strategy of the United States in the Pacific Ocean, where it attempts to limit China’s naval activities in potential future conflict.

Newsweek‘s map shows the Hai Yang 25‘s transit in the Tokara Strait, where the ship entered the waterway from the East China Sea and sailed into waters west of Kuchinoerabu Island. It left the island of Yakushima’s southwestern waters and sailed southward after reaching the Philippine Sea.

The spokesperson referenced the United Nations Convention on the Law of the Sea, UNCLOS. The treaty, adopted in 1982, frames a comprehensive regime of law and order in the world’s oceans and seas, establishing rules governing all uses of the oceans and their resources.

Transit passage applies to straits that are used for international navigation between one part of the high seas or an exclusive economic zone and another, according to UNCLOS. All ships have this freedom of navigation “solely for the purpose of continuous and expeditious transit” of the straits.

The treaty states that ships shall “proceed without delay through or over the strait” while exercising the right. Foreign ships, including hydrographic survey ships, may not conduct research or survey activities during transit passage without the “prior authorization” of the states bordering straits.

UNCLOS grants all ships the right of innocent passage through the territorial waters of another state as long as the transit is continuous and expeditious and not prejudicial to the coastal state’s peace, good order, or security. Both China and Japan have signed and ratified this treaty.

According to a paper published by the U.S. State Department in 1998, Japan extended its territorial waters to the usual 12 nautical miles in 1977, except for specified designated areas in five international straits, which created territorial water limits between three and 12 nautical miles.

Straits affected by this decision are the Tsushima Strait’s eastern and western channels, the Osumi Strait, the La Perouse Strait (also known as the Soya Strait), and the Tsugaru Strait. Japan has made its territorial waters claim less than 12 nautical miles in these waterways to maintain high seas corridors.

They are also the major gateways for China to deploy its fleets beyond the country’s surrounding waters in the East China Sea and the South China Sea. Both the Osumi Strait and the Miyako Strait, situated to the north and the south of the Tokara Strait, are part of the first island chain.

Newsweek‘s map shows the locations of these Japanese straits. The Tsushima Strait connects the East China Sea and the Sea of Japan, while the La Perouse Strait and the Tsugaru Strait, situated to the north and the south of Japan’s Hokkaido Island, link the Sea of Japan and the Pacific Ocean.

The Chinese navy has been operating in the waters to the east of the first island chain for years as Beijing continues to expand its fleets to contend with the U.S. Navy and its allied naval forces.

Japan’s Defense Ministry reported on Monday that two Chinese naval vessels passed through the Miyako Strait on Sunday as they sailed from the East China Sea to the Philippine Sea. They were identified by their hull numbers as Type 052C destroyer Jinan and Type 903A replenishment ship Chaohu.