Japan Submarine Capabilities

Although Japan has been operating submarines since as early as 1905, the face of its submarine force along with its greater naval forces, known as the Japan Maritime Self-Defense Force (JMSDF), has greatly changed during its history. As the world's 7th largest Exclusive Economic Zone (EEZ) with 90% of its oil and 60% of its food imported by sea, the island nation of Japan has always placed great value on its naval forces. [1] However, recent "grey zone" conflicts with China and continued tensions with North Korea have underscored the importance of Japan's naval forces. As such, it is no surprise that the JMSDF is the dominant branch of Japan Self-Defense Force (JSDF). Japan's submarine fleet is expected to play a large role in that force, having recently begun expansion for the first time in 36 years. [2]

In 1905, the Imperial Japanese Navy acquired five Holland-class vessels from the American company, Electric Boat. [3] Soon afterwards, Japan began constructing its own submarines, and by the beginning of World War II, it possessed one of the world's most powerful submarine fleets. Following Japan's defeat in World War II the Imperial Japanese Navy was dissolved, and in 1954 the Self-Defense Forces Law created the Japanese Maritime Self-Defense Force. Since that time, Japan has actively maintained a small but very technically advanced submarine fleet, allocating the necessary resources to ensure that Japan's limited number of submarines would be among the most advanced in the world. In 2010, in response to increased tensions with China surrounding the Senkaku Islands and continued North Korean bellicosity, Japan chose to expand its submarine fleet for the first time since 1976. [4] Specifically, the 2010 and subsequent 2014 National Defense Program Guidelines (NDPG) committed to expand the Japanese submarine fleet to include 1 additional squadron, for a total of 6, and six additional active submarines, for a total of 22. [5]

The JMSDF currently operates two submarine flotillas, made up of five squadrons operating eighteen diesel-electric attack submarines, of which sixteen are considered to be in service. The First and Second Submarine Flotillas are based at Kure and Yokosuka, respectively, with all three classes of submarines constructed by Mitsubishi Heavy Industries and Kawasaki Shipbuilding Corporation at their respective shipyards in Kobe, Japan. [6] The fleet currently consists of two Harushio-class submarines - one used for training purposes and the second acting as an AIP (Air Independent Propulsion) test platform - as well as eleven Oyashio-class and five Soryu-class submarines. [7]

The two Harushio-class vessels currently operated by the JMSDF, the JDS Fuyushio and JDS Asashio, were commissioned in 1995 in 1997, respectively. [8] They are the only two vessels that remain of the original seven Harushio-class vessels. The other five, which entered service in the early 1990s, were decommissioned at a rate of one per year starting in March 2009. Capable of carrying up to 75 sailors, Harushio -class submarines were equipped with six 533mm torpedo tubes, which could deploy Type 80 and Type 89 torpedoes or sub-launched UGM-84 Harpoon missiles. [9] In March 2000, The JDS Asashio was re-designated as a training submarine (TSS-3601), and then subsequently reconverted to serve as a test-platform for Air-Independent Propulsion technology. Finally in March 2011, the last Harushio-class vessel was technically removed from active service, as the JDS Fuyushio was also re-designated a training platform. [10]

Following the Harushio-class, Japan began vigorous production on the Oyashio-class submarine, commissioning one per year from March 1998 to March 2008. The Ovashio-class currently makes up the majority of Japan's submarine fleet, with eleven such vessels in service. Unlike previous JMSDF submarine designs, which were teardrop-shaped, the Oyashio-class hull incorporates a leaf coil hull design. [11] However, while the Ovashio-class represents a significant departure from its predecessor in terms of hull design and automation, the weapons systems remained the same between the two classes, equipped with six 533mm torpedo tubes, accommodating Type 89 torpedoes or sub-launched UGM-84 Harpoon missiles. [12]

The most recent additions to Japan's submarine fleet are its six Souryu-class submarines, which represent the next evolution of Japanese submarines following the Oyashio-class. Designed to be an improvement on the Oyashio design, the Souryu-class builds on the weapons systems and capabilities of its predecessor by introduction of the AIP system, which significantly improves its capabilities in terms of power-projection and counter-detection. Unlike Japan's previous submarine classes, which were produced at a rate to match the rate of decommissioning of older classes, the Souryu-class submarine is being produced at a rate of one per year, greatly outstripping the decommissioning rate of the Oyashio-class, with the ultimate goal of expanding the JMSDF submarine fleet to 22 by the early 2020's. [13]

While it is at this point uncertain what to expect for the JMSDF submarine fleet following the conclusion of the current phase of procurement, it is very likely, given the evolving security situation vis-à-vis China, that the Japanese submarine fleet will at least maintain its current strength, and may continue to expand with another submarine modernization or redesign program. This expansion in Japan's submarine fleet is simply the latest shift in the slow evolution from the passive approach Japan adopted following WWII. The changing security situation in East Asia combined with increasing American reluctance to intervene, seem to be forcing the JSDF to expand its naval activities. [14] This was most clearly demonstrated by the decision in April 2014 to abolish the long-standing restrictions on exporting military equipment and technology. [15] Negotiations recently began between Japan and Australia regarding the purchase of submarine technology, or perhaps even fully engineered vessels. [16]

[1] "Jane's World Navy: Japan," IHS Jane's, 24 April 2014, www.janes.com.
[2] "Japan to beef up submarines to counter Chinese Power," The Chosun Ilbo, 26 July 2010, www.chosun.com.
[3] James Delgado, Silent Killers: Submarines and Underwater Warfare, (Osprey Publishing, 2011), 118.
[4] "Japan to beef up submarines to counter Chinese Power," The Chosun Ilbo, 26 July 2010, www.chosun.com.
[5] Japanese Ministry of Defense, "National Defense Program Guidelines for FY 2011 and beyond," 17 December 2010, pp. 20; Japanese Ministry of Defense, "National Defense Program Guideline for FY 2014 and beyond," 17 December 2013, pp. 31.
[6] "Harushio-class submarine SS," Seaforces-online Naval Information, 2013, www.seaforces.org.
[7] "Jane's World Navy: Japan," IHS Jane's, 24 April 2014, www.janes.com.
[8] "Harushio Class Submarine - SS," Seaforces.org, Accessed: 25 May 2014, www.seaforces.org.
[9] "Harushio Class Submarine - SS," Seaforces.org, Accessed: 25 May 2014, www.seaforces.org.
[10] "Jane's Underwater Warfare Systems - Submarines, Japan," IHS Jane's, 8 July 2010, www.janes.com.
[11] "Oyashio Class Submarines, Japan," Naval Technology.com, Accessed: 26 May 2014, www.naval-technology.com.
[12] "Oyashio Class Submarines, Japan," Naval Technology.com, Accessed: 15 May 2014, www.naval-technology.com.
[13] Kate Tringham, "Japan launches sixth Souryo-class submarine," IHS Jane's, 7 November 2013, www.janes.com.
[14] Nobuhiro Kubo, Linda Sieg, and Phil Stewart, "Japan, U.S. differ on China in talks on 'grey zone' military threats," Reuters, 9 March 2014, www.reuters.com.
[15] "Jane's Sentinel Security Assessment: Defense Production and R&D - Japan," IHS Jane's, 4 April 2014, www.janes.com.
[16] Tim Kelly and Matt Siegel, "Japan & Australia consider submarine deal that could rattle China," Reuters, 28 May 2014, www.reuters.com.

June 30, 2014
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The submarine proliferation resource collection is designed to highlight global trends in the sale and acquisition of diesel- and nuclear-powered submarines. It is structured on a country-by-country basis, with each country profile consisting of information on capabilities, imports and exports.

This material is produced independently for NTI by the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies at Monterey and does not necessarily reflect the opinions of and has not been independently verified by NTI or its directors, officers, employees, or agents. Copyright 2018.