Japan Maritime Self-Defense Force

History

Origin

Following Japan's defeat in World War II, the Imperial Japanese Navy was dissolved by the Potsdam Declaration acceptance. Ships were disarmed, and some of them, such as the battleship Nagato, were taken by the Allied Powers as reparations. The remaining ships were used for repatriation of the Japanese soldiers from abroad and also for minesweeping in the area around Japan, initially under the control of the Second Bureau of the Demobilization Ministry. The minesweeping fleet was eventually transferred to the newly formed Maritime Safety Agency, which helped maintain the resources and expertise of the navy.

Japan's 1947 Constitution was drawn up after the conclusion of the war, which contained Article 9, which specified that "The Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as a means of settling international disputes." The prevalent view in Japan is that this article allows for military forces to be kept for the purposes of self-defense. Due to Cold War pressures, the United States was also happy for Japan to provide part of its own defense, rather than have it fully rely on American forces.

In 1952, the Safety Security Force was formed within the Maritime Safety Agency, incorporating the minesweeping fleet and other military vessels, mainly destroyers, given by the United States. In 1954, the SSF was separated, and the JMSDF was formally created as the naval branch of the Japan Self-Defense Forces (JSDF), following the passage of the 1954 Self-Defense Forces Law.

The first ships in the JMSDF were former U.S. Navy destroyers, transferred to Japanese control in 1954. In 1956, the JMSDF received its first domestically produced destroyer since World War II, Harukaze. Due to the Cold War threat posed by the Soviet Navy's sizable and powerful submarine fleet, the JMSDF was primarily tasked with an anti-submarine role.

Post-Cold War

Following the end of the Cold War, the role of the JMSDF has vastly changed. In 1991, after international pressure, the JMSDF dispatched four minesweepers, a fleet oiler (JDS Tokiwa) and a minesweeping tender (JDS Hayase) to the Persian Gulf in the aftermath of the Gulf War, under the name of Operation Gulf Dawn, to clear mines sown by Saddam Hussein's defending forces. Starting with a mission to Cambodia in 1993 when JSDF personnel were supported by JDS Towada, it has been active in a number of UN-led peacekeeping operations throughout Asia.

In 1993, the JMSDF commissioned its first Aegis-equipped destroyer, Kongō. It has also been active in joint naval exercises with other countries, such as the United States. The JMSDF has dispatched a number of its destroyers on a rotating schedule to the Indian Ocean in an escort role for allied vessels as part of the UN-led Operation Enduring Freedom.

21st century

The JMSDF, along with the Japan Coast Guard, has also been active in preventing North Korean infiltrators from reaching Japan and on 22 December 2001, engaged and sank a North Korean spy ship in the Battle of Amami-Ōshima.

In 2002, the JMSDF deployed ships to the Arabian Sea in support of Operation Anaconda during the War in Afghanistan.

In August 2003, a new "helicopter carrier" class was ordered, the Hyūga-class helicopter destroyer. Due to the size and features of the ship, including a full-length flight deck, it was classified as a helicopter carrier by Lloyd's Register — similar to the United Kingdom's HMS Ocean. The Self-Defense Forces are not allowed to possess ICBMs, strategic bombers, or "attack aircraft carriers". However, according to the Japanese government's definition, "attack aircraft carriers" refer specifically to carriers designed solely for nuclear bombers to conduct nuclear strikes. Aircraft carriers equipped with helicopters, conventional fighter jets or attack aircraft—whether they are small light carriers or large nuclear-powered carriers—are not considered illegal.

With an increase in tensions with North Korea following the 1993 test of the Nodong-1 missile and the 1998 test of the Taepodong-1 missile over northern Japan, the JMSDF has increased its efforts in air defense. A ship-based anti-ballistic missile system was successfully test-fired on 18 December 2007 and has been installed on Japan's Aegis-equipped destroyers.

In November 2009, the JMSDF announced plans for a larger "helicopter carrier", the Izumo-class helicopter destroyer. In 2025, these vessels were re-classified as "multi-role aircraft-carrying cruisers" as part of their conversion to operate F-35B V/STOL fighters. This made them de facto aircraft carriers. To avoid controversy, the ruling parties initially classified the vessels "multi-purpose operation destroyers" and then, in 2025, as "multi-role aircraft-carrying cruisers". The first of these ships was laid down in 2012 and was launched on 6 August 2013. Two vessels of the class were in service as of 2025.

The submarine fleet of the JMSDF consists of some of the most technologically advanced diesel-electric submarines in the world. This is due to careful defense planning in which the submarines are routinely retired from service ahead of schedule and replaced by more advanced models. In 2010 it was announced that the Japanese submarine fleet would be increased in size for the first time in 36 years.

Capabilities

The JMSDF has an official strength of 50,000 personnel, but presently numbers around 50,800 active personnel.

As a result of continuing effective defense investment due to Japan's economic development and an end to the Cold War, the JMSDF became the world's fourth largest navy by total tonnage by 2000. Japan has the eighth largest Exclusive Economic Zone (EEZ) in the world, and the JMSDF is responsible for protecting this large area. As an island nation, dependent on maritime trade for the majority of its resources, including food and raw materials, maritime operations are a very important aspect of Japanese defense policy.

The JMSDF is known in particular for its anti-submarine warfare and minesweeping capabilities. Defense planners believe the most effective approach to combating hostile submarines entails mobilizing all available weapons, including surface combatants, submarines, patrol planes, and helicopters. They are also known to operate at least fourteen listening stations all over the country that have ELINT and marine surveillance radar warning systems.

Historically, the Japan Air Self-Defense Force (JASDF) has been relied on to provide air cover at sea, a role that is subordinate to the JASDF's primary mission of air defense of the home islands. Extended patrols over sea lanes are beyond the JASDF's current capabilities.

The Japanese fleet's capacity to provide ship-based antiaircraft warfare protection is limited by the absence of full-sized aircraft carriers, though its destroyers and frigates equipped with the Aegis combat system provide a formidable capability in antiaircraft and antimissile warfare. Additionally, the deployment of F-35B V/STOL fighters on the Izumo-class aircraft-carrying cruisers are force multipliers for the Japanese fleet, allowing force projection of Japan's sizable surface combatant force far from home waters. Acquiring such capabilities has been contentious in the context of Japan's "passive" defense policy after World War II.

Long-range strike capability will be introduced as soon as Tomahawk cruise missiles are deployed on JMSDF destroyers.

Activities

International activities

Destroyers and combat support ships of Japan Maritime Self-Defense Force were dispatched to the Indian Ocean from 2001 to 2008 to participate in OEF-MIO (Operation Enduring Freedom-Maritime Interdiction Operation). Their mission is to prevent the marine transportation of illegal weapons and ammunition, and the drugs which fund terrorist activity. Since 2004, the JMSDF has provided ships of foreign forces with fuel for their ships and ship-based helicopters, as well as freshwater.

This was the third time Japanese military vessels had been dispatched overseas since World War II, following the deployments of mine-sweeping units during the Korean War and the Persian Gulf War. The law enabling the mission expired on 2 November 2007, and the operation was temporarily canceled due to a veto of a new bill authorizing the mission by the opposition-controlled upper chamber of the Japanese Diet.

In January 2010, the defense minister ordered the JMSDF to return from the Indian Ocean, fulfilling a government pledge to end the eight-year refueling mission. Prime Minister Yukio Hatoyama refused to renew the law authorizing the mission, ignoring requests from the American government for continuation. Both the Western alliance country typified by the Royal Australian Navy and the Royal Danish Navy, doing friendship activities in the Indian Ocean.

In May 2010, Japan announced its intention to build a permanent naval base in Djibouti, from which it will conduct operations to protect merchant shipping from Somali pirates.

The JMSDF and the U.S. Navy frequently carry out joint exercises and "U.S. Navy officials have claimed that they have a closer daily relationship with the JMSDF than any other navy in the world". The JMSDF participates in RIMPAC, the annual multi-national military exercise near Hawaii that has been hosted by the U.S. Navy since 1980. The JMSDF dispatched a ship to the Russian Vladivostok harbor in July 1996 to participate in the Russian Navy's 300th Anniversary Naval Review. In return, Admiral Vinogradov, an Udaloy-class destroyer, called at Tokyo Bay in June 1997. The JMSDF has also conducted joint naval exercises with the Indian Navy.

RIMPAC: Japan Maritime Self-Defense Force participated in RIMPAC after 1980.

JMSDF Aegis Afloat

On 16 December 2022, the Japanese Cabinet approved a trio of defense-related policy documents, including its new National Security Strategy (NSS or 国家安全保障戦略), the strategic guideline document for the Japanese government's policies regarding diplomacy, defense, and economic security for the next decade. Based on the NSS, the National Defense Strategy (NDS or 国家防衛戦略) document outlined Japan's defense policy goals and the means to achieve them while the Defense Buildup Program (DBP or 防衛力整備計画) document outlined the scale of the introduction of specific defense equipment within the budgetary objectives. According to the Defense Buildup Program document, the JMSDF will increase the number of Aegis-equipped guided-missile destroyers (DDG) from the current 8 to 10 warships, as well as the introduction of two Aegis system-equipped vessels (ASEV) to be deployed in ballistic missile defense (BMD) operations. By the end of the decade, the JMSDF will operate 12 ships equipped with Aegis Weapon System (AWS) and likewise plans to replace its fleet of older, less capable destroyers and destroyer escorts with Mogami-class frigates.

On 23 December 2022, the Japanese Ministry of Defense's 2023 budget and program guidance documented provided examples of operations (運用の一例) for the Aegis-equipped naval forces of the Japanese Maritime Self Defense Force (MSDF). The two ASEV warship would be exclusively tasked for dedicated ballistic missile defense (BDM) missions (BMD等) and operate off the Korean peninsula in the Sea of Japan, allowing the other Aegis guided-missile destroyers to meet other contingencies (侵攻阻止) while operating independently to maintain the maritime domain awareness (MDA) and keep the sea lines of communication (SLOC) open in the East China Sea southwest of the Japanese home islands (pictured).

On 6 October 2022, five warships from the United States, Japan, and South Korea held a multilateral ballistic missile defense exercise in the Sea of Japan (pictured) as part of the military response to ongoing North Korean intermediate-range ballistic missile tests over the Japanese home islands. On 16 November 2022, the guided-missile destroyer Maya fired an SM-3 Block IIA missile, successfully intercepting the target outside the atmosphere in the first launch of the missile from a Japanese warship. Two days later, the Haguro fired an SM-3 Block IB missile with a successful hit outside the atmosphere. Both test firings were conducted at the U.S. Pacific Missile Range Facility on Kauaʻi Island, Hawaii, in cooperation with the U.S. Navy and U.S. Missile Defense Agency. This was the first time the two ships conducted SM-3 firings in the same time period, and the tests validated the ballistic missile defense capabilities of Japan's newest Maya-class destroyers.

Equipment

Ships and submarines

The ship prefix JDS (Japanese Defense Ship) was used until 2008, at which time JMSDF ships started using the prefix JS (Japanese Ship) to reflect the upgrade of the Japanese Defense Agency to the Ministry of Defense. The JMSDF operates two multi-purpose operation destroyers (de facto aircraft carriers), two helicopter carriers (called helicopter destroyers), 36 destroyers, six frigates, six destroyer escorts, 23 attack submarines, 19 mine countermeasure vessels, six patrol vessels, three landing ship tanks, seven training vessels, and a fleet of various auxiliary ships. The fleet has a total displacement of approximately 624,000 tonnes, excluding auxiliary vessels.

Aircraft

The Japan Maritime Self-Defense Force aviation maintains a large naval air force, including 201 fixed-wing aircraft and 145 helicopters. Most of these aircraft are used in anti-submarine warfare operations.

Organization, formations and structure

The JMSDF is commanded by the Chief of the Maritime Staff. Its structure consists of the Maritime Staff Office, the Self Defense Fleet, five regional district commands, the air-training squadron and various support units, such as hospitals and schools. The Maritime Staff Office, located in Tokyo, serves the Chief of Staff in commanding and supervising the force.

The Self-Defense Fleet, headquartered at Yokosuka, consists of the JMSDF's military shipping. It is composed of Fleet Surface Force, based in Yokosuka, Sasebo, Maizuru and Kure, the Fleet Air Force headquartered at Atsugi, the Fleet Submarine Force based at Yokosuka and Kure, the Mine Warfare Force based at Yokosuka and the Fleet Training Command at Yokosuka.

In March 2018, Ryoko Azuma became the first female squadron commander in the JMSDF. Her unit includes the flagship Izumo, the largest warship in the JMSDF. She commands four warships making up a division with a total of 1,000 crew members.

Each Escort Flotilla is formed as a fleet of eight destroyers and eight on-board helicopters. Each force is composed of one helicopter destroyer (DDH)/aircraft carrier (CVM) acting as a command ship, two guided-missile destroyers (DDG) and five standard or ASW destroyers (DD). The JMSDF is planning to reorganize the respective Escort Flotillas into a DDH/CVM group and DDG group, enabling faster overseas deployments.

Prime Minister of Japan

Minister of Defense

JMSDF Chief of Staff / Maritime Staff Office

Self-Defense Fleet

Fleet Surface Force

Escort Flotilla 1 (Yokosuka)

Escort Division 1: CVM-183 Izumo; DDG-179 Maya; DD-101 Murasame; DD-107 Ikazuchi (Yokosuka)

District Forces

Five district units act in concert with the fleet to guard the waters of their jurisdictions and provide shore-based support. Each district is home to a major JMSDF base and its supporting personnel and staff. Each district is home to one or two regional escort squadrons, composed of two to three destroyers or destroyer escorts (DE). The destroyers tend to be of older classes, mainly former escort force ships. The destroyer escorts tend to be purpose built vessels. Each district has a number of minesweeping ships.

Fleet Air Force

The Fleet Air Force is tasked with patrol, ASW and rescue tasks. It is composed primarily of seven aviation groups. Prominent bases are maintained at Kanoya, Hachinohe, Atsugi, Naha, Tateyama, Omura and Iwakuni. The Fleet Air Force is built up mainly with patrol aircraft such as the Lockheed P-3 Orion, rescue aircraft such as the Shin Meiwa US-1A and helicopters such as the Mitsubishi SH-60J. In the JMSDF, helicopters deployed to each escort force are actually members of Fleet Air Force squadrons based on land.

Special Forces and Security Units

Special forces and tactical boarding units consist of the following:

Special Boarding Unit (SBU): The JMSDF's designated special forces unit, trained for high-risk, non-compliant maritime interdictions, hostage rescue, and counter-terrorism.

Maritime Interception Teams (MIT) (Tachiri Kensatai): Standard, shipboard VBSS (Visit, Board, Search, and Seizure) teams organically assigned to individual destroyers and frigates. Composed of regular ship crew members with specialized security training, they are used for routine, compliant boarding operations and maritime law enforcement.

Ranks

The rank insignia of commissioned officers.

The rank insignia of non-commissioned officers and enlisted personnel.

Culture and traditions

Flag and insignia

The Imperial Japanese Navy first adopted the off-set naval ensign Jūrokujō-Kyokujitsu-ki (十六条旭日旗) on May 15, 1870, and it was used until the end of World War II in 1945. On June 30, 1954, when the JSDF was established, the JSDF and JGSDF adopted a different rising sun flag with 8-rays and an 8:9 ratio. The old off-set navy flag with the sun and 16 rays was re-adopted as the ensign of the Maritime Self-Defense Force, but it was modified with a brighter red color. The original flag is darker red (RGB #b12d3d) while the post-WW2 version is brighter red (RGB #bd0029).

The "Z" maritime signal flag was used by Admiral Tōgō as a victory flag at the Battle of Tsushima, and has been used on occasion by the JMSDF as an unofficial ensign to avoid controversy with the Rising Sun flag.

Music and traditions

The JMSDF has maintained some historic links with the Imperial Japanese Navy. Today's JMSDF continues to use the same martial songs, naval flags, signs, and technical terms as the IJN. The JMSDF still uses the Warship March, the old service march of the IJN, as its official service march. It also maintains the IJN bugle calls tradition, as every ship and shore establishment command maintain a platoon or squad of bugle players.

The JMSDF band has also added popular anime soundtracks to their repertoire, with the soundtrack from Space Battleship Yamato becoming a signature song for the band.

Collaboration

The JMSDF started an official collaboration with the warship game franchise Kantai Collection, notably using girls from the franchise as mascots for their ship using the same name. For example, JS Kaga has the ship girl wearing the JMSDF women uniform as her official mascot, and the game introduced the "Kaga Kai Ni Go" ship remodel, notably featuring amament from the early JMSDF, and a flight deck copied from JS Kaga. The girl Shigure is even the official mascot for the Sasebo Naval District.

Food

Curry was introduced to Japan by the British Royal Navy. It soon gained popularity among the civilian population and it's not clear whether it became popular as returning Japanese military veterans introduced it, or that the Japanese military adopted it as a staple due to its popularity, however the Japanese Navy discovered its high thiamine content help combat beriberi, then a constant threat due to the difficulty in providing fresh vegetables on long sea voyages, and dictated it should be served weekly. It quickly became known as a quintessential Navy dish, as Navy cooks adapted the dish to the Japanese palate and further cemented its place in Japanese cuisine.

Up until her decommission, the JS Hachijō (MSO-303) continued the tradition of serving curry every Friday. Each ship's galley would unofficially competing to make the best curry in the fleet, with recipes closely guarded as a matter of pride.

Ship names

The ship prefix JDS (Japanese Defense Ship) was used until 2008, at which time JMSDF ships started using the prefix JS (Japanese Ship) to reflect the upgrade of the Japanese Defense Agency to the Ministry of Defense.

Ships of the JMSDF, known as Japan Ships (自衛艦; Ji'ei-Kan), are classified according to the following criteria:

Recruitment and training

JMSDF recruits receive three months of basic training followed by courses in patrol, gunnery, minesweeping, convoy operations, and maritime transportation. Flight students, all upper-secondary school graduates, enter a two-year course. Officer candidate schools offer six-month courses to qualified enlisted personnel and those who have completed flight school.

Graduates of four-year universities, the four-year National Defense Academy, and particularly outstanding enlisted personnel undergo a one-year officer course at the Officer Candidate School at Etajima, site of the former Imperial Naval Academy. The JMSDF operates a staff college in Tokyo for senior officers.

The large volume of coastal commercial fishing and maritime traffic around Japan limits in-service sea training, especially in the relatively shallow waters required for mine laying, minesweeping, and submarine rescue practice. Training days are scheduled around slack fishing seasons in winter and summer—providing about ten days during the year.

The JMSDF maintains two oceangoing training ships and conducted annual long-distance on-the-job training for graduates of the one-year officer candidate school.