On June 15, 2025, the Japan Maritime Self-Defense Force (JMSDF) frigate Mogami (FFM) conducted its first mine disposal training using an unmanned surface vehicle (USV) off the coast of Iwo-To Island in the Pacific Ocean.
The Mogami-class FFM—where “FF” stands for frigate and “M” denotes mines and multi-purpose capability—is designed not only for coastal defense but also for mine disposal in shallow waters, a mission traditionally assigned to medium-sized minesweepers (Mine Sweeper Coastal: MSC). As the Mogami-class is built with a steel hull, it is inherently more vulnerable to magnetic influence mines. To address this, the ships are equipped with a range of unmanned systems that enable mine detection and disposal from a safe stand-off distance.
Mine detection is carried out using the hull-mounted mine warfare sonar system OQQ-11 and the OZZ-5 unmanned underwater vehicle (UUV). The OZZ-5 is an autonomous UUV developed by the former Technical Research and Development Institute (TRDI), now integrated into the Acquisition, Technology & Logistics Agency (ATLA), and manufactured by Mitsubishi Heavy Industries (MHI). It is equipped with both a high-frequency synthetic aperture sonar (HFSAS) developed by France’s Thales and a low-frequency synthetic aperture sonar (LFSAS) developed by Japan’s NEC, enabling detection of difficult targets such as bottom and buried mines. The UUV operates along a pre-set route, and after recovery aboard the FFM, its sonar data is analyzed onboard to determine the presence of mines.
In 2021, a bilateral research and prototyping project was launched between the Japanese and French defense authorities to develop next-generation mine detection technologies. The project aims not only to improve the detection accuracy of the OZZ-5 but also to enable real-time onboard analysis of sonar data by the UUV itself, eliminating the need for shipboard data processing.
For mine disposal, the JMSDF employs a USV manufactured by Japan Marine United (JMU), which is deployed and recovered from the stern of the FFM. The USV is equipped with expendable mine disposal (EMD) charges mounted at the stern, allowing it to remotely detonate identified mines.
Future JMSDF Mine Warfare Posture
Japan is placing increased emphasis on strengthening and modernizing its mine warfare capabilities, particularly in preparation for a potential armed conflict with China in a Taiwan contingency. The JMSDF is gradually retiring its aging wooden-hulled Sugashima-class MSCs and plans to transfer their mine disposal missions to the Mogami-class FFMs. For shallow-water mine disposal, the JMSDF will rely on a mix of Mogami-class FFMs, as well as the wooden-hulled Hirashima-class and GFRP-built Enoshima-class MSCs. Deep-water mine disposal will be handled by the Awaji-class Mine Sweepers Ocean (MSO), which have been entering service since 2017.
The organizational structure of JMSDF mine warfare units is also undergoing significant reform. Until now, JMSDF minesweepers have been assigned to two separate commands: the Mine Warfare Force under the Self Defense Fleet, and the Minesweeper Divisions under regional District Commands. However, under the FY2025 defense budget, this system is being restructured as part of a broader transformation of JMSDF surface forces. Moving forward, all JMSDF surface combatants will be consolidated under a new “Surface Fleet.” Minesweepers will be concentrated under a subordinate formation within this fleet, known as the Amphibious Mine Warfare Group, enhancing the JMSDF’s unified mine disposal capability.
