[Discussion] Japan Commissions Advanced Taigei-Class Submarine, Enhances Maritime Defense

[Uncrowned Guard]

Japan Bolsters Maritime Defense with Fourth Taigei-Class Submarine

On March 6, 2025, the fourth submarine of the Taigei-class, Raigei, was officially commissioned into the Japan Maritime Self-Defense Force (JMSDF) at the Kawasaki Heavy Industries' Kobe Shipyard. The event was marked by a ceremony, attended by top-ranking defense and maritime officials. The JMSDF's flag was also presented to the submarine in a traditional show of induction into the fleet.

Specifications and Capabilities of the Newly Inducted Submarine

The JS Raigei, SS-516 – a 3000-ton diesel-electric attack submarine- represents a further enhancement to Japan's maritime defense prowess. The 84-meter-long submarine is powered by two Kawasaki 12V 25/31 diesel engines and a single-propulsion motor hooked to a single-shaft system. Its state-of-the-art lithium-ion batteries offer a clear advantage over previous classes in operational flexibility and underwater endurance.

Additionally, the Raigei submarine showcases enhanced stealth and detection capabilities, including an upgraded sonar suite and a new combat management system fostering improved situational awareness. Being capable of housing female crew members, the Raigei presents a progressive move in the naval fleet of Japan.

Raigei's Armament and Its Construction Timeline

Raigei is equipped with six 533mm HU-606 torpedo tubes, capable of deploying Type 18 torpedoes and UGM-84L Harpoon Block II anti-ship missiles. These armaments equip the submarine with a robust offensive stance against surface or subsurface threats, while its sophisticated electronic warfare and countermeasure systems enhance Raigei's survivability amidst enemy detection and attacks.

The submarine was built under the JMSDF's Mid-Term Defense Program. The fifth submarine of the class, Chogei, which was launched in October 2024, is expected to join the service in 2026.

Role and Deployment of Raigei Amidst Rising Naval Threats

Assigned to the 1st Submarine Squadron of Submarine Flotilla 1, stationed at the Kure Base in Hiroshima Prefecture, Raigei is anticipated to play an indispensable role in Japan's maritime security strategy. This comes as a response to the escalating naval activities in the region and the projected expansion of the Chinese Navy in the Western Pacific.

A Transition From Soryu-Class to Taigei-Class Submarines

The Taigei-class marks an evolved generation of submarines, following the Soryu-class by integrating updated stealth, endurance, and detection capabilities. This leap forward is realized with the implementation of lithium-ion battery technology that enhances longer submerged endurance and a fiber-optic array technology-based sonar system for improved operational effectiveness.

Japan’s Changing Submarine Doctrine and The Future of Taigei-Class

Today, the Taigei-class hosts five planned installations, with four already in service and the fifth foreseen to enter service in 2022. As the region encounters growing security concerns, these submarines, stationed at JMSDF’s Kure and Yokosuka bases, are set to play a pivotal role in countering looming maritime threats. Japan's sole familiarity with lithium-ion battery technology, a perk enabling longer patrols and increased operational flexibility, underlines the instrumental role of these submarines in curbing the expanding presence of the Chinese Navy in the Western Pacific.

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