It is with great honor that I contribute this article to the renowned U.S. military publication UNDERSEA WARFARE Magazine as commander of the Japan Maritime Self Defense Force’s (JMSDF) Fleet Submarine Force. My heartfelt gratitude goes to Rear Admiral Merz, Commander, U.S. Submarine Group 7, a sister command to JMSDF Fleet Submarine Force, for providing me with this opportunity.

This year marks the 60th anniversary since the inception of JMSDF’s submarine force. When adding 40 years from the Imperial Japanese Navy (IJN), later succeeded by the JMSDF, the total number of years that Japan operated submarines comes to 100 years. Serving as Submarine Force Commander during this memorable time is a true privilege, and I have great admiration for the accomplishments of our predecessors who steadily built the history of Japan’s Submarine Force and for the Submariners who are currently attending to their missions, quietly, somewhere deep in the sea.

History of Japan’s Submarine Force

The history of Japan’s Submarine Force begins with the IJN, later succeeded by JMSDF. The IJN Submarine Force was launched when Holland-class submarines were delivered in 1905, five years after the birth of the U.S. Submarine Force. The IJN’s five Holland-class submarines were procured for use in the Russo-Japanese War, which had broken out the previous year. While these submarines were never deployed during the war, the IJN Submarine Force continued to grow, absorbing foreign technology and uniquely evolving into a world-renowned 65-vessel force when it faced the Pacific War.

Rather than attacking enemy sea lanes during the submarine warfare in the Indian and Pacific Oceans during WWII, the IJN focused on winning a decisive surface fleet battle using key warships. Its submarine doctrine placed heavy emphasis on the attrition of enemy warships.

As the war took a turn for the worse for the IJN, submarines were used for delivering supplies to frontline islands and for search and security missions, resulting in needless submarine losses. This was further compounded by a lag in submarine innovation and mass production, causing the IJN Submarine Force to be decimated by allied antisubmarine warfare in terms of quantity, tactics, and technology by mid-war. The IJN Submarine Force suffered losses of over 80 percent by the war’s conclusion, which also marked the end of the IJN Submarine Force’s 40-year history.

In 1952, seven years after the end of WWII, the JMSDF was established, with anti-submarine warfare (ASW) as its primary mission. As a submarine would be necessary for conducting ASW training, the United States loaned the JMSDF the ex-USS Mingo (SS 261) in January 1955. A crew consisting primarily of former IJN Submariners came together and traveled to New London, Conn., to receive training at the U.S. Naval Submarine School. Upon completion in August of the same year, Mingo, renamed Kuroshio, was turned over to the crew. It was at this point that Japan’s Submarine Force began etching its place in history again for the first time since 1945, after a 10-year pause.

JS Takashio (SS 597) arrives at Pearl Harbor Aug. 11, 2016.


In 1960, Japan quickly embarked on domestic submarine production with pre-war submarine manufacturer Kawasaki Heavy Industries, starting construction of its first post-war submarine, Oyashio. Another domestic submarine manufacturer, Mitsubishi Heavy Industries, also began building submarines. To date, these two companies have produced a total of 51 submarines, each carrying a piece of JMSDF Submarine Force history. Japan’s 1977 National Defense Program Guidelines expressed that 16 submarines would be needed to adequately defend the waters in and around Japan.


JMSDF’s first teardrop-shaped submarine, Uzushio, modeled after the U.S. Navy’s Barbel-class, was commissioned in 1971 with significant advancements in underwater detection and maneuvering capabilities. Thereafter, the JMSDF continued making advancements in sound quieting in the Harushio class, side arrays for improved detection in the Oyashio class, and undersea maneuverability using Stirling air-independent propulsion (AIP) on the Soryu class.

The JMSDF Fleet Submarine Force was established in 1981 with two submarine groups and a Submarine Training Center (STC) under its command, becoming the first JMSDF fleet with a submarine school. The STC was pivotal in establishing the foundation for Japan’s submarine force, including Submariner training and development and supporting the integration of new systems.

The JMSDF has long cooperated with the U.S. Navy. It has sent one submarine to Hawaii annually since 1963 to receive U.S. Navy training and mentorship. This has increased to two submarines beginning in 2013. The JMSDF participated in RIMPAC from 1986 through 2010 and continues to reinforce cooperation at sea by conducting various PASSEX training exercises in and near Japan’s territorial waters and exchanging information between the two commands. In addition to working with the U.S. Navy, the JMSDF is participating in events such as the biennial joint submarine rescue training PACIFIC REACH with the United States, Australia, South Korea, and Singapore, as well as the Asia Pacific Submarine Conference.

Current Undertakings by JMSDF Fleet Submarine Force
Japan’s 2010 National Defense Program Guidelines increased the number of submarines needed to adequately defend Japan’s waterways from 16 to 22, noting needs to reinforce underwater intelligence, surveillance, reconnaissance, and patrols. That this policy decision produced so little domestic debate is extraordinary given Japan’s current fiscal situation. This appears to indicate a widely held understanding among Japan’s citizens of the effectiveness and value provided by a strong submarine force. In light of the current maritime security challenges, the JMSDF Submarine Force recognizes the trust that Japanese citizens are placing in it as represented by this increase.

Despite this 40-percent increase in the number of submarines, it won’t have much effect without advancing the force’s capabilities as well. The most critical issue concerning force augmentation is Submariner training and operational experience. The STC has already begun bolstering its training posture to accommodate an increase in recruits entering the program, implementing policies to accelerate promotions to next rank for all dolphin insignia holders and promoting strong personal accountability from each and every service member.

There are countless other issues being addressed: procurement of new torpedoes, expansion of mooring and supply facilities, improving operational availability through standardized repairs, etc. Vital to advancing the submarine force’s capabilities is the JMSDF’s plans to advance to the next generation of submarine. JMSDF military leaders must take into consideration capabilities required of a new submarine and how and in what situations these submarines would operate with U.S. and other partner submarine forces. The JMSDF Submarine Force must also be able to clearly communicate its requirements to the engineers and shipyards.


JS Takashio (SS 597) arriving at Joint Base Pearl Harbor-Hickam.


Clearly, the JMSDF Submarine Force is in the midst of transformation and expansion. It is receiving technological and operational support from the U.S. Navy, which is pivotal in implementing these upgrades. Despite Japan having built its own conventional submarines and the U.S. Submarine Force having only nuclear-powered submarines, there remains an extremely close relationship between the JMSDF Submarine Force’s and the U.S. Submarine Force’s leadership, engineering arms, undersea medical arms, shipyards, and submarine weapons manufacturers. Without a doubt, this relationship created Japan’s submarine force. The JMSDF recognizes that everyone taking part in this cooperative relationship is a partner bound by shared values, and relationships fostering open discussions between uniformed, civilian, public, and private sectors must be maintained to bring these improvements to fruition through united effort.


The JMSDF Fleet Submarine Force came to life through abundant experience and advanced technology that former IJN Submariners gained from U.S. Navy support after WWII. A borrowed U.S. Navy motto, “know your boat” decorates the entrance of STC along with the reminder, “We are at the center of battle.” This is to relay to new Submariners the lesson from IJN days that all decisions must be centered on the battle.

The JMSDF Submarine Force continues to expand its knowledge and effort guided by these mottoes as it continues to contribute to the defense of Japan with demonstrated operational capabilities and safety. In the JMSDF Submarine Force’s 60-year history, not a single submarine has been lost due to an accident, and each submarine has remained commissioned through its designed service life.

Of course, a successful past by no means guarantees perpetual success, but it does solidify the foundation on which we stand. Admittedly there remain some equipment, operations, and crew training issues that need attention, but as long as the JMSDF Submarine Force humbly recognizes these issues, accepts the challenge of transformation, and continues to improve its submarines, it will be able to capitalize on the force’s undersea potential. Continuous effort and expansion of combat capabilities are prerequisites to deepening cooperation with the U.S. Navy’s Submarine Force and, most importantly, it is the force’s unwavering contribution to the security of Japan.