Japan puts third Taigei Class submarine into service.

The Japan Maritime Self-Defense Force (JMSDF) has commissioned the third of its Taigei-class diesel-electric attack submarines, which feature greater underwater endurance than previous vessels.

Named JS Jingei (with pennant number SS 515), the new Taigei-class ship joined Escort Division 4 at Yokosuka Naval Base, Kanagawa Prefecture, shortly after being delivered by shipbuilder Mitsubishi Heavy Industries (MHI) at its facilities in the city of Kobe on March 8.

The first submarine of this class, Taigei, was converted into a test submarine on the same day, so Japan continued to maintain a total fleet of 22 submarines.

According to the JMSDF, the new submarine has a crew of around 70, an overall length of 84 m, a beam of 9.1 m, a draft of 10.4 m and a standard displacement of around 3,000 tonnes, meaning it is slightly larger than the well-known previous SSKs of the Soryu class, which are 84 m long, 9.1 m wide, 10.3 m draft and have a standard displacement of 2,950 tons.

The Taigei class has exclusive women’s compartments for the first time, including living space for up to six women, according to the JMSDF.

Jingei means “swift whale” in Japanese and was the name given to an imperial ocean-going yacht and an auxiliary submarine during the Imperial Japanese Navy. All Taigei-class submarines incorporate “Gei” (whale) in their names, following the “Shio” (tide) and “Ryu” (dragon) series seen on previous JMSDF submarines. “Taigei” itself means “great whale.”

The new submarine, which cost about 69.9 billion yen ($473 million) to build, is powered by a diesel-electric engine that generates 6,000 hp. Its maximum speed underwater is 20 knots.

The JMSDF has stated that all Taigei-class vessels are equipped with lithium-ion batteries instead of lead-acid ones, as are the latest two Soryu-class vessels for the JMSDF: Oryu (SS 511) and Toryu (SS 512).


So far, Japan is the only known country to have installed lithium-ion batteries in SSKs. South Korea is expected to be the next country to do so with the second batch of KSS-III class submarines (also known as Dosan Ahn Chang-ho) in the late 2020s.

According to the Japanese Ministry of Defense, the new Taigei class employs a “compact” and “highly efficient” electricity storage and supply system that prolongs the submarine’s underwater endurance without the need to increase the size of the vessels.

The class also employs a new combat management system (CMS) that combines advanced integrated sensors, command and control, and weapon docking systems, the MoD said.

Furthermore, it adopts an improved snorkel system to reduce signatures and a new generation sonar system based on fiber optic array technology to improve detection ability.

The Taigei class employs the same anti-torpedo countermeasures system that the last four Soryu class ships have incorporated. It uses Japan’s newest torpedo, called the Type 18, which succeeds the previous Type 89. Initially called “G-RX6”, the new torpedo will feature improvements in several areas, such as propulsion, target detection and processing.

The class can also deploy the UGM-84L Harpoon Block II anti-ship missile against surface targets. The range of this missile is 248 km, enough for Japan to acquire a “counter-strike capability”, something that remains the subject of heated debate in Tokyo.

In May 2015, the US State Department approved the possible sale of these submarine-launched missiles to Japan. At the time it was estimated that the deal would be worth $199 million. The Japanese government had requested 48 UGM-84L Block II missiles to complement the JMSDF’s existing capability of UGM-84C and RGM-84C Harpoon missiles, the US Defense Security Cooperation Agency said.

The first Taigei-class submarine, named Taigei (SS 513), entered service in March 2022. The second in the class, named Hakugei (SS 514), entered service in March 2023. The fourth in the class, Called Raigei, it was launched by Kawasaki Heavy Industries (KHI) in October 2023 and is expected to enter service in March 2025. Hakugei means “white whale,” while Raigei means “thunder whale.”

The Ministry of Defense has allocated funds for the construction of four further submarines of the class – SS 517, SS 518, SS 519 and SS 520 – with MHI building the first and third submarines and KHI the second and fourth.

The JMSDF has not officially decided how many Taigei-class submarines will be built. However, considering that the JMSDF has built about 10 submarines for each class so far, the total number of Taigei-class submarines is likely to be approximately the same. In other words, the Ministry of Defense and the JMSDF are likely to maintain the current pace of replacing aging Oyashio-class submarines.

Under the current Defense Strengthening Programme, approved by the government in December 2022, the 11th Taigei-class submarine is likely to be built as the last of the class during fiscal year 2027.

Most recently, on December 22, 2023, the Ministry of Defense in Tokyo secured 95 billion yen for fiscal year (FY) 2024 starting in April to build the eighth SSK, or SS 520, of the class.

Construction of the next class of submarines is likely to begin from the next fiscal year 2028 budget. This means that the Ministry of Defense and the JMSDF must now seriously consider the next-generation submarine.

Japan puts third Taigei Class submarine into service.

The Taigei class and the new security environment

Considering the security environment surrounding Japan, China and Russia are increasing their nuclear submarine forces. North Korea also intends to acquire nuclear submarines equipped with cruise missiles with a range of more than 1,500 km that can reach the Japanese archipelago. As the possibility of an emergency in the Taiwan Strait becomes increasingly real, the operational missions and maritime zones that JMSDF submarines can undertake are expanding.

In such a severe security situation, the development of the new class submarine must be in line with the Defense Strengthening Program, which requires the acquisition of counterattack capabilities, which implies the possibility of attacking enemy territory.

The Defense Strengthening Program specifically states: “To achieve submarine supremacy, the MSDF will develop a submarine (SS) equipped with a Vertical Launch System (VLS) with the objective of acquiring counter-missile carrying submarines.”

More than a few military experts in Tokyo have pointed out that it is difficult for the Taigei class to carry the VLS due to the relatively small size of its hull and its limited power supply compared to nuclear submarines, although as of the fourth Taigei class vessel New high-power diesel engines and related equipment are being installed.

To build a new submarine with a vertical launcher capable of launching long-range missiles from underwater, it is essential that the hulls of the new Japanese submarines be larger than now and ensure additional power supply capacity.

Furthermore, it is also inevitable that Japan’s new submarine will have to carry state-of-the-art high-power sonar and several unmanned underwater vehicles (UUVs), all of which will require a greater amount of energy than now.

By Kosuke Takahashi