According to reports from Japan’s Self-Defense Forces, a Chinese People’s Liberation Army Navy (PLAN) submarine support vessel of the Dakai-class was detected transiting the Tsushima Strait last week—marking the first recorded instance of a vessel of this class passing through the area. Far from being an isolated event, this deployment is part of a broader pattern of recent Chinese naval movements near Japanese waters and archipelagos.
As detailed by the Joint Staff of Japan’s Self-Defense Forces, the submarine support ship—identified by hull number 841—was observed sailing eastward approximately 205 nautical miles west of the Goto Islands, Japan. During its passage, the vessel proceeded northeast through the Tsushima Strait and entered the Sea of Japan. Notably, the day prior, a group of PLAN surface vessels had also been sighted sailing northeast, about 55 nautical miles west of the Goto Islands. That group subsequently passed through the Tsushima Strait as well, also heading into the Sea of Japan.
The sighted vessel belongs to the Dakai-class, the most modern class of submarine rescue and support ships in the PLAN fleet. This class was designed to provide technical, logistical, and operational support to submarines—especially during extended missions or maritime emergencies. The vessel with hull number 841 identified in this deployment is believed to be the second of an estimated three vessels of the class, having entered active service in late 2024.
This detection—particularly involving a submarine support vessel of the Chinese PLAN—transiting the Tsushima Strait is considered an unusual move and has further heightened Japan’s concerns over China’s expanding naval activity near its territory. The strait itself is a strategic maritime corridor in the region, and such a transit may be interpreted as a show of presence intended to assert influence.
Finally, the presence of a submarine support vessel in these waters could also suggest an enhancement of China’s long-range undersea operational and sustainment capabilities in the Sea of Japan, potentially indicating support for concurrent deployments of attack or ballistic missile submarines in the region.
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