Japan launches final Mogami-class frigate JS Yoshii to monitor nearby seas.

On December 22, 2025, Mitsubishi Heavy Industries held a naming and launching ceremony at its Nagasaki Shipyard for JS Yoshii, the twelfth and final Mogami-class frigate built for the Japan Maritime Self-Defense Force.

On December 22, 2025, Mitsubishi Heavy Industries (MHI) held a naming and launching ceremony at its Nagasaki Shipyard for the JS Yoshii, the twelfth and final Mogami-class frigate built for the Japan Maritime Self-Defense Force. Following this event, which marked the formal completion of hull construction for the FFM program, the vessel will now enter the outfitting and trial phases ahead of its planned delivery in fiscal year 2026.
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This is the first time the name Yoshii has been used for a vessel of the Maritime Self-Defense Force or the former Imperial Japanese Navy, and it is also the first Mogami-class ship named after a river from the Chugoku region. (Picture source: Shinjiro Koizumi)

During the ceremony, Japan’s new Minister of Defense, Shinjiro Koizumi, announced the ship’s name as Yoshii, marking the moment when the hull entered the water and formally completed the construction phase. Around 200 attendees were present, including senior defense officials and industrial representatives, reflecting the importance of the event within Japan’s naval shipbuilding cycle. With the launch completed, the JS Yoshii transitioned into the next phase, focused on onboard installation and testing. Delivery to the Japanese Navy is planned within fiscal year 2026, with commissioning expected around March 2027 once the final steps are completed.

The JS Yoshii is the twelfth and final ship of the Mogami-class multi-mission frigate program, also known as the FFM series, closing the initial batch planned by Japan. Construction took place at the Nagasaki yard of Mitsubishi Heavy Industries, which built ten of the twelve ships in the class, confirming its central role in the program. The vessel carries the pennant number FFM-12 and represents the last hull ordered under the original Mogami-class framework that began entering budgets in 2018. With the JS Yoshii now launched, the program shifts from hull construction to final outfitting and acceptance across the remaining ships. The completion of this twelfth hull marks a clear transition point between the initial Mogami-class and the upcoming New FFM-class, also known as the Upgraded Mogami-class, selected by Australia in August 2025.

The Yoshii measures 133 meters in length and 16.3 meters in beam, with a displacement of approximately 3,900 tonnes and a hull depth of around 9 meters. Like earlier Mogami-class frigates, the ship is designed to operate with a crew of roughly 90 personnel, reflecting a deliberate emphasis on automation and integrated systems to reduce manpower compared with earlier Japanese escort ships, such as the Abukuma-class and the Asagiri-class. The design also incorporates features intended to reduce detectability, aligning with Japan’s broader effort to complicate the tracking and targeting of surface combatants. The development of the Mogami-class aims to support both routine surveillance and maritime security missions while remaining capable of higher-intensity operations. Within this framework, the ship was therefore structured to perform anti-submarine, anti-air, and anti-surface roles while also absorbing tasks previously assigned to dedicated mine warfare vessels.

Propulsion for the Mogami-class frigate follows a classic combined diesel and gas (CODAG) arrangement, delivering a total output of about 70,000 horsepower. In this arrangement, the gas turbines provide high output for rapid transit while the diesel engines support economical cruising, resulting in a maximum speed of around 30 knots, or roughly 55.6 kilometers per hour. The class’s integrated combat system is designed around an advanced combat direction system that merges data from multiple sensors, fire control systems, and communications networks to coordinate weapon engagements and situational awareness.

A 16-cell Mk-41 vertical launching system (VLS) forms the core of its air defense capability, and surface engagements are supported by the Mk-45 Mod-4 62-caliber 5-inch gun, which provides both naval gunfire support and surface strike capability. Additional fittings include two triple torpedo tubes for short-range torpedoes, two quadruple launchers for Type 17 anti-ship guided missiles, a SeaRAM launcher with 11 missiles for close-in air defense, and two 12.7 mm remote-controlled machine guns. The hull design also includes a flight deck and hangar space to operate a single Mitsubishi SH-60L patrol helicopter, extending the ship’s reach for surveillance and anti-submarine operations.

Mine warfare represents another significant element of the Mogami-class frigate, reflecting a strategic shift in how such missions are resourced within Japan's escort fleet. Instead of relying solely on dedicated mine countermeasure vessels, these frigates integrate an onboard mine countermeasure sonar system that provides sub-surface detection of moored and bottom mines, feeding data into classification and avoidance protocols. A simplified mine-laying system allows the ship to emplace mines when operationally necessary, contributing to area denial and defensive minefield establishment.

Acknowledging the growing role of unmanned systems, the Japanese frigate also incorporates a suite of autonomous platforms tailored to mine missions, including the OZZ-5 unmanned underwater vehicle designed to carry remote sensors and effectors into hazardous zones. Plans for future capability growth include the installation of a variable depth sonar to improve sub-surface detection in varying thermal layers, and a towed array sonar system to enhance long-range acoustic sensing against submarines and other underwater contacts. By embedding these diverse mine warfare and anti-submarine systems into a general-purpose frigate hull, the Mogami-class assumes roles previously assigned to specialized mine countermeasure ships while maintaining core surface, air, and undersea combat competencies.

The name Yoshii originates from the Yoshii River in Okayama Prefecture, which flows from Mount Mikuniyama through eastern Okayama before reaching Kojima Bay, continuing the Mogami-class tradition of naming ships after Japanese rivers. This is the first time the name Yoshii has been used for a vessel of the Maritime Self-Defense Force or the former Imperial Japanese Navy, and it is also the first Mogami-class ship named after a river from the Chugoku region. Alongside Yoshii, the eleventh ship JS Tatsuta, forms the final pair of the class, with a combined construction cost stated at approximately ¥116.6 billion. Following the launch, Yoshii will proceed through outfitting, harbor trials, and sea trials before acceptance, with plans indicating assignment to a newly established Patrol and Defense Group. With all twelve Mogami-class ships now launched, Japan is preparing to move forward with a follow-on New FFM-class featuring expanded capabilities, while an improved Mogami-derived design has also been selected by Australia, linking the program to future international cooperation.

Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.