As the Japan Maritime Self-Defense Force (JMSDF) has consolidated the use of the Sōryū-class submarines while simultaneously advancing the induction of the even more modern and capable Taigei class, the oldest units of its submarine fleet are being progressively retired from service. This is reflected in the gradual decommissioning of the earliest Oyashio-class submarines, with the retirement ceremony of submarine SS-592 Uzushio taking place yesterday, December 19, following 25 years of service with the force.
At present, the Japan Maritime Self-Defense Force operates one of the largest and most advanced conventionally powered submarine fleets in the Pacific, as well as worldwide. This capability is the result of the country’s decades-long incremental and continuous approach to submarine force development.
To provide a general overview, Japan’s attack submarine fleet is structured across several classes, namely: the Oyashio class, originally composed of eleven units commissioned between 1998 and 2008; followed by the Sōryū class, comprising twelve units commissioned between 2009 and 2021; and the most modern Taigei class, currently in the process of induction, with four units in service out of the eight planned, while two additional submarines have been recently launched.
As can be seen, in a planned manner and in step with the introduction of new units, the Oyashio class has been gradually handing over the baton to a new generation. In this process, the lead submarine of the class, TSS-3608 Oyashio (ex SS-590), was decommissioned in March 2023 after fulfilling, in keeping with Japanese tradition, training ship duties.
Accordingly, yesterday—and following the decommissioning in March of the second unit, TSS-3609 Michishio (ex SS-591)—the decommissioning and retirement ceremony of the third submarine of the class, SS-592 Uzushio, took place in the city of Yokosuka, marking the end of its 25 years of service.
The ceremony, during which the Japan Maritime Self-Defense Force ensign was permanently lowered, was presided over by Vice Admiral Koji Yagi, Commander of the Yokosuka Naval District. He praised the role performed by the submarine and its crew over 25 years, during which they defended Japan and its maritime spaces from beneath the sea.
Subsequently, following the presentation of the ensign to Vice Admiral Yagi, the final commanding officer of Uzushio, Commander Yoshihiro Eiya, stated: “Today we conclude 25 years of missions and proceed with her decommissioning. Uzushio was truly an excellent ship. She trained numerous crew members, and those same sailors continue today to play a vital role, quietly, beneath the sea.”
Finally, of the eight submarines of the class still in service, two have followed the path of the earliest units and now perform training and instructional roles for future submarine personnel, namely TSS-3610 Makishio and TSS-3611 Isoshio, which have been in service since 2001 and 2002, respectively.
As for the remaining six submarines, it is likely that some will follow a similar end-of-service path in training roles, while others—such as the aforementioned Uzushio—will be decommissioned as the new Taigei-class submarines are launched and inducted into active service.
About the Oyashio class:
Developed to replace the earlier Harushio class, the eleven Oyashio-class submarines were built by Kawasaki Shipbuilding Corporation and Mitsubishi Heavy Industries between 1994 and 1998.
With a full-load displacement of 3,500 tons, the class measures 81.7 meters in length with a beam of 8.9 meters, and is powered by two Kawasaki 12V25S diesel engines, achieving a surface speed of 12 knots and up to 20 knots submerged.
In terms of armament, the submarines are equipped with six torpedo tubes for Type 89 torpedoes, along with the capability to launch UGM-84 Harpoon anti-ship missiles.
Cover photograph used for illustrative purposes.
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