Japan completes the series of 12 Mogami-class destroyers.

The Japan Maritime Self-Defense Force has completed a series of 12 Mogami-class destroyers after Mitsubishi Heavy Industries held a naming ceremony and launched the final vessel, JS Yoshii (FFM-12), in Nagasaki. This is the largest shipbuilding program in Japan since World War II, with a significantly shortened construction time.

JS Yoshii completes the Mogami-class destroyer series.

According to information from the Japan Maritime Self-Defense Force and Defense Minister Shinjiro Koizumi, the naming and launching ceremony of JS Yoshii took place at the Mitsubishi Heavy Industries shipyard in Nagasaki. The Defense Minister personally attended the ceremony.

The ship was named "Yoshii" (よしい) after a river in Okayama Prefecture. This name had never been used by the Imperial Japanese Navy before, suggesting Japan's novel approach to naming its modern destroyer fleet.

After its launch, JS Yoshii will be towed to the dock for further completion of the remaining items. According to plan, the ship is expected to join the fleet in 2026. The keel-laying ceremony took place on July 3, 2024, and just 17 months later, the ship was launched, reflecting the rapid progress of the construction program.

Key specifications of the Mogami class

The Mogami-class destroyers are designed as multi-purpose vessels, of moderate size but optimized for sensors and weaponry. Key specifications include:

• Standard displacement: 3,900 tons
• Full-load displacement: approximately 5,500 tons
• Ship length: 132.5 - 133 m
• Width: 16.3 m
• Draft: 9 m
• Crew: approximately 90 people

This configuration allows the Mogami-class to maintain sea endurance at a level suitable for patrol, escort, and near-shore defense missions, while optimizing operating costs with a relatively small crew size.

Weapon systems: multi-purpose configuration on a medium airframe.

Surface fire and fire support

The main armament of the Mogami-class ships is the 127 mm Mk 45 Mod 4 naval gun manufactured by BAE Systems. This gun is capable of firing at targets at sea, in the air, and along the coast, providing direct fire support for shore forces as well as engaging small and medium-sized surface targets.

Medium and short-range air defense

To counter airborne and missile threats, the ship is equipped with the Mk 41 vertical launch system with 16 launch tubes. The 16 tubes allow for the integration of various types of anti-aircraft or anti-submarine missiles depending on the configuration, creating a medium-range defense layer around the ship formation.

At close range, the destroyer uses the SeaRAM anti-aircraft missile-gun system to protect against cruise missiles, low-flying targets, and close-range threats. The combination of the Mk 41 and SeaRAM gives the ship a multi-layered air defense system, increasing its survivability against air attacks.

Anti-ship capability

The Mogami-class ships' surface attack capability is provided by eight Type 17 (SSM-2) anti-ship cruise missiles. These are the primary weapons for attacking enemy surface vessels, allowing the ships to destroy surface targets at ranges exceeding the range of their main guns.

Anti-submarine warfare and countering asymmetric threats.

In its anti-submarine role, the Mogami-class is equipped with torpedo tubes for Type 12 lightweight torpedoes, used to attack enemy submarines at close to medium range. These torpedo tubes complement the ship's anti-submarine warfare capabilities, in conjunction with sensors and anti-submarine helicopters.

To counter asymmetrical attacks from small armed boats or high-speed approaching targets, two remotely controlled combat modules equipped with 12.7 mm machine guns are also mounted on the deck. These remotely controlled weapon stations allow for accurate firing in rough seas and reduce risks to the crew.

Mine-laying capability and maritime defense mission.

A notable feature of the Mogami-class design is the integration of a simple mine-laying device. This allows the ship to participate in establishing mine defenses, enhancing its ability to blockade and control key maritime areas. This makes the Mogami-class a versatile platform, capable of both escort duties and deploying for defensive operations in territorial waters.

Air force component on board the ship

The air component on a Mogami-class destroyer revolves around a single Mitsubishi SH-60K/L multi-purpose helicopter. This helicopter can perform a variety of missions such as reconnaissance, search and rescue, anti-submarine warfare, and target designation support for onboard weapons.

Progress of new ship construction and old ship replacement program

Construction of the Mogami-class destroyers began in 2019 as part of a program to replace the Hayabusa-class missile frigates and Abukuma-class escort frigates. The goal is to build a modern surface fleet capable of performing multiple missions on a single hull.

To expedite the process, Japan opted for simultaneous construction in pairs. In 2019, the first two ships of the series – Mogami and Kumano – were launched on October 29th and 30th, respectively.

The launch dates for the two vessels were swapped: the Kumano was launched on November 19, 2020, while the lead vessel, the Mogami, was not officially launched until March 3, 2021. The delay was due to damage to a Rolls-Royce MT30 gas turbine during testing on the test bench, when the equipment collided with a faulty part of the test bench, requiring technical repairs before continuing.

Following the initial phase, construction of the next 10 ships proceeded continuously without significant interruption. According to Militarnyi, this is the largest series of ships built in Japan since the end of World War II, demonstrating a focus on investing in a multi-purpose surface fleet.

Significance for Japan's combat capabilities

With the completion of the 12 Mogami-class destroyers, the Japan Maritime Self-Defense Force now possesses a class of medium-sized surface vessels that combine air defense, anti-submarine warfare, anti-ship warfare, and mine-laying capabilities on a single platform. The short construction time of the JS Yoshii – just 17 months from keel laying to launch – demonstrates that the Japanese shipbuilding industry has established a stable production process for this class of ships.

JS Yoshii's commissioning in 2026 will complete the program, adding another multi-purpose destroyer to the maritime defense network, particularly for patrol and protection missions in the waters surrounding Japan.