Facing Security Challenges, Japan Expands Its Navy and Acquires Amphibious Capabilities


The Japanese Izumo-class helicopter destroyer JS Izumo.

With rising tensions in East Asia, many countries are facing increasing pressure to bolster their militaries. Japan, however, is in a unique situation due to its post-World War II pacifism and reliance on America for defense. While the mutual defense treaty with the US ensures American assistance should Japan be attacked, the reliability of that backup could be jeopardized should the US become embroiled in other conflicts, and Japan still needs its own forces to deal with day-to-day security. North Korea presents an acute threat and China is also undertaking rapid military development, especially in the air and naval spheres, with increasingly-sophisticated technology that will continue to erode Japan’s qualitative edge. Due to the size of China’s economy and its consequently higher military spending, this trend is unlikely to abate.

Whereas North Korea’s gains have mostly been in ballistic missile technologies, China’s rising naval and aerial power has been felt on a regular basis by the Japanese Self-Defense Force (JSDF). In 2016, the Japanese Air Self-Defense Force (JASDF) intercepted 851 Chinese aircraft, a record figure which reflects China’s increasing capabilities and ambitions. In the naval realm, the Senkaku/Diaoyu islands dispute has been steadily brewing since 2012; the below chart illustrates the number of vessels entering the islands’ territorial sea over time. Japan also has ongoing (albeit dormant) disputes with Russia, Taiwan, and South Korea.


In order to effectively counter the rising assertiveness of its neighbors, Japan is embarking on a modest quest to modernize its military. Being an island nation with crucial interests in shipping and fishing, the bulk of this push has fallen on the Japanese Maritime Self-Defense Force (JMSDF). The remainder of this article will explore specific JMSDF procurements and examine their significance.

Two New Izumo-class Helicopter Carriers


A JMSDF SH-60K anti-submarine warfare helicopter.

Japan’s decision to expand its naval aviation fleet is perhaps the most visible element of this modernization drive. The Izumo class is referred to by Japan as a class of “helicopter destroyers,” but they are de facto carriers as they lack any substantial armament other than short-range missiles for self-defense. The Izumo class displaces around 27,000 tons fully loaded and reaches 30 knots at maximum speed. Their standard aviation outfit is seven SH-60K and seven MCH-101 helicopters. The SH-60K is a medium-lift anti-submarine helicopter based on the American MH-60 and license produced by Mitsubishi Heavy Industries. It has an all-composite rotor for improved performance and an active dipping sonar for anti-submarine duties. The MCH-101 is a medium-lift mine countermeasures helicopter based on the AW101 and license produced by Kawasaki Heavy Industries.

As such, the Izumo class is primarily an anti-submarine and demining platform. This differs from American helicopter-carrying amphibious assault ships, which are designed for power projection. The introduction of the Izumo class will expand the JMSDF’s capabilities against China’s subsurface force, which includes a number of new nuclear attack submarine (Type 093 and 095) and air-independent-propulsion (Type 039A) classes. Despite the intended role of anti-submarine warfare and mine warfare, helicopter carriers are remarkably versatile; the Izumo class could also be used in humanitarian assistance and air assault operations should the need arise, and could launch F-35B STOVL aircraft with some modification. Note, however, that Japan has no plans, as of yet, to procure F-35Bs, so any discussion of launching jets from the Izumo class is speculative. While the F-35B would be a significant addition to the JMSDF’s capabilities, it is an expensive proposition and would essentially nullify Japan’s claims that the Izumo class is not an offensive platform.

Four New Soryu-class Submarines

JS_Hakuryu_(SS-503)_arrives_at_Joint_Base_Pearl_Harbor-Hickam_for_a_scheduled_port_visit,_-6_Feb._2013_(YP255-023) (1)

Soryu-class submarine JS Hakuryu visits Pearl Harbor. Note the distinctive X-shaped dive planes.

In addition to the two Izumo-class carriers entering service, Japan is currently building four new Soryu-class air-independent propulsion (AIP) submarines. Boats of the class displace 4,200 tons submerged and can reach 20 knots submerged. Primary armament is six torpedo tubes capable of firing heavyweight torpedoes as well as Harpoon anti-ship missiles. The Stirling AIP system used by the Soryu class was designed by Kockums of Sweden and allows the submarines to recharge their lead-acid batteries quietly while submerged, greatly increasing submerged endurance relative to a conventional diesel-electric submarine. Stirling AIP is known to be remarkably quiet — the US Navy even borrowed a Swedish Gotland-class submarine equipped with it to provide a cutting-edge adversary in its anti-submarine warfare exercises.

The final two boats of the Soryu class will have their Stirling AIP system replaced by a bank of lithium-ion batteries, the same type of battery used in electric cars and handheld electronics. If all goes as planned, the JMSDF will be the first navy in the world to field a lithium-ion propelled submarine. This new drivetrain will increase endurance and probably decrease sonic signature as well.

While conventional subs face endurance disadvantages relative to nuclear boats in blue-water operations, they are ideally suited to missions in the littorals, where their maneuverability, small size, and low sonic signature make detection of small AIP boats remarkably difficult. Given the challenges Stirling AIP submarines have posed for even the most experienced Western navies, it is a fair assumption that the PLAN would have serious difficulties countering the Soryu class. In addition to providing a silent deterrent against surface warships, the Soryu class will also contribute to anti-submarine operations — a critical mission given the large submarine fleets operated by regional adversaries such as China, North Korea, and Russia.

Two Asahi-class (25DD) destroyers


Akizuki-class destroyer JS Fuyuzuki. The Asahi class is based on the Akizuki class.

The Asahi-class (also knows as the 25DD-class) destroyer is a moderately-sized multi-mission destroyer class designed to complement Japan’s larger Kongo and Atago-class Aegis destroyers. The Asahi class is based on the previous Akizuki class and displaces around 5,000 tons. The vessels are fitted with two LM2500 gas turbines in a relatively rare combined gas-electric and gas (COGLAG) hybrid powertrain which allows the class to reach 30 knots. Its main weapons system is a 32-cell Mk 41 Vertical Launch System (VLS) which is loaded with quad-packed Evolved Sea Sparrow Missiles (ESSMs) and Vertical Launch Anti-Submarine Rockets (VL-ASROCs). Other anti-submarine weapons systems include two triple lightweight torpedo launchers and an SH-60K anti-submarine helicopter. Anti-ship capability is provided by eight Type 90 anti-ship missiles in static box launchers.

With its large quantity of medium-range ESSMs, the Asahi class is well-suited for escort duty and capable of defending against massed cruise missile attacks. Since the PLA has a formidable land-based, air-based, surface-based, and submarine-based cruise missile arsenal, the Asahi class’s large quantity of ESSMs will provide important resistance to saturation attacks. Moreover, Japan’s Kongo-class destroyers are not yet equipped with Aegis Baseline 9 and thus cannot engage cruise missile threats while in ballistic missile defense mode, a shortcoming which the Asahi class will help mitigate when the two operate in tandem.

Like the Izumo class, the Asahi class carries an SH-60K anti-submarine helicopter for long-range detection and patrol duty. The fact that most of Japan’s recent naval procurements, including the Asahi class, Izumo class, and Soryu class, are competent anti-submarine platforms indicates the seriousness with which Japan seems to be treating China’s developments in subsurface warfare.

A New Amphibious Rapid Deployment Brigade

Exercise Iron Fist 2016: PHIBLEX Recon Insert

JGSDF soldiers and US Marines train together.

Because its military has been self-defense focused since World War II, the Japan Ground Self-Defense Force (JGSDF) has traditionally lacked in expeditionary amphibious strength. However, with the escalation of territorial disputes over remote islands, Japan has decided it can no longer afford to ignore power projection capabilities and has begun to raise an Amphibious Rapid Deployment Brigade (ARDB).

The ARDB is an amphibious force equipped with Amphibious Assault Vehicles (AAVs) and MV-22 Osprey tiltrotors, closely mirroring a US Marine brigade in form and function. Unsurprisingly, the Japanese troops which will constitute the ARDB have been training extensively with the Marines in preparation for the formation of the first ARDB in 2018. The JGSDF’s goal is to eventually have three such brigades.

Because many of Japan’s disputed territories are remote and lack a garrison, they could be easily overrun by a determined adversary. The ARDB will provide a rapid counterattack capability in the event such a territory should be taken. In peacetime, the ARDB could also provide significant utility as a disaster relief force, especially when traditional infrastructure is rendered unusable.

Constitutional tensions

Japan’s post-war constitution renounces armed conflict as an instrument of foreign policy and states “land, sea, and air forces, as well as other war potential, will never be maintained.” As soon as 1954, the United States realized it needed Japan to field a military capable of self-defense against communist threats and set about convincing Japan to rearm itself despite Article IX. In recent times, the interpretation of Article IX has evidently been rather loose, as the JSDF maintains a formidable military complete with modern planes, ships, and armor. Nevertheless, despite Japan’s renewed focus on defense, the country’s military budget remains approximately 1% of GDP, lower than even Germany.

Japan is still sensitive to the constitutionality of its military and has traditionally avoided offensive assets such as bombers, aircraft carriers, etc. Japanese president Shinzo Abe has been trying to build up the military and increase Japan’s participation in international defense activities by amending Article IX but has so far not seen much success — popular opinion on Article IX amendment is split and Abe’s junior coalition partner, Komeito, is pacifist (at least ostensibly). However, with a resounding 2/3 majority for Abe’s Liberal Democratic Party and Komeito after the most recent election, amendment is certainly on the table — if Abe can push it through, the JMSDF may see an even further expansion of its capabilities, albeit to the chagrin of its neighbors, many of whom fear the return of a militaristic Japan.

3 Comments on "Facing Security Challenges, Japan Expands Its Navy and Acquires Amphibious Capabilities"

  1. I’ve recently come across whitefleet.net and I am impressed with your work.

    About this article, are the decks of the Izumo class “helicopter destroyers” treated to resist the heat of the MV-22’s? The America class LHA had to have its deck reinforced not only because of the F-35B exhaust but because of the MV-22 exhaust as well. If the JDSF wants to model their ARDB after the Marine Corps, it would make sence that they should be able to deploy their MV-22s off of Japan’s Izumos.

    • Hello Dan,

      Thanks for your kind words about the website. I have not yet found any primary source information on the Izumo class’s deck coating. However, Japan’s Hyuga-class helicopter carriers have launched MV-22s, and I would assume that the Izumo class either has this capability now or could be easily modified to have it in the future, since the JMSDF certainly knew of the Osprey while the Izumo class was being designed and built. However, some sources seem to imply that the deck coating which allows the Ospreys also makes it possible to launch F-35Bs, which contradicts the notion that the Izumo class would need a new coating for the JSF. It is possible the deck coatings applied for the Osprey would allow the F-35B to fly but only if the deck is given time to cool in between sorties. In truth, most of the sources I’ve found seem to be rather speculative and do not provide any references or much concrete information about the Izumo class’s deck. In light of this, I will remove the mention of deck coating from the article, as it’s a somewhat minor question anyways — there are much larger barriers to Japan operating F-35Bs, such as cost and politics.

      In any case, it is important to keep in mind that the Izumo class is not really designed as an amphibious warfare platform in the first place, and thus MV-22s will probably never be a significant part of its air wing. The ARDB will more likely deploy from Japan’s Osumi-class LSTs, which are designed for amphibious warfare (with a well deck) and are capable of launching Ospreys.

      Hope that answers your question and I will post another reply if I stumble upon any new information.

  2. Thabk you for your very informative reply. I wonder if the JDSF will try to arm their MV-22s in a similar way that the Marine Corps are experimenting with. Either way keep up the good work. Looking forward to your next article.

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