Tag Archive for: Japan Self-Defense Forces

Japan and Australia can fill each other’s defence gaps

Japan and Australia talk of ‘collective deterrence,’ but they don’t seem to have specific objectives. The relationship needs a clearer direction.

The two countries should identify how they complement each other. Each country has two standout areas: Japan has strengths in air and missile defence and in shipbuilding, whereas Australia needs help in both; and Australia has strengths in cybersecurity and its distance from China, both of which offer advantages for Japan.

It’s true that both nations have recently strengthened their special strategic partnership to the point where it has begun to show alliance-like characteristics, such as commitments to consult during regional crises. Yet practical coordination has barely begun. Discussions on bilateral cooperation often end at increasing interoperability—but to what end?

During the Japan-Australia Dialogue and Exchange program, hosted by the United States Studies Centre and the Japan Foundation from July to August last year, I engaged with many Japanese and Australian experts on security issues, including a Taiwan contingency. While many underscored the need for the two countries to deepen defence ties and prepare to fight together should a crisis erupt, there was little clarity on how exactly they should coordinate.

Although some studies are conducted behind closed doors, the overall lack of discussion stems from several factors. Japan has a limited understanding of Australia’s defence capabilities, and the Japanese defence community primarily focuses on implementing established policy. These factors have contributed to stagnation in finding new strategic opportunities.

In Australia, a shortage of Japan-focused security expertise and a preoccupation with the trilateral framework that includes the United States as well as Japan have constrained deeper thinking around bilateral cooperation.

Japanese and Australian foreign and defence ministers said in November that the countries were refining the scope, objectives and forms of their cooperation, a development that will help shape bilateral defence relations. This was in support of what they called strengthening collective deterrence. But all this work is still general rather than specific in nature, and discussion among strategists has been minimal.

Defence cooperation between nations with comparable military power and a reciprocal security relationship typically takes two forms: force aggregation, which enhances overall military capacity through joint operations; and complementary cooperation, which mitigates vulnerabilities by leveraging respective strengths.

Japan and Australia have primarily focused on force aggregation by emphasising interoperability, but this has limitations. China has an overwhelming numerical advantage, with about 1100 fighter aircraft and more than 140 major surface warships. Conversely, Japan has 300 fighters and 52 surface combatants, while Australia has about 100 fighters and plans to expand its fleet from 9 to 26 ships. Given this disparity, simply combining forces would do little to shift the strategic balance without further integration with US forces. Even then, the military challenges would remain immense.

Complementary coordination is needed, too. Both countries face the challenge of China, but their operational priorities differ. While Japan focuses on the East China Sea and the western Pacific, Australia can secure sea lanes of communication in the Indian Ocean and the South Pacific and disrupt adversary lanes. This would help ensure Japan’s access to vital resources and ammunition, sustaining its ability to keep fighting while weakening China’s. Japan’s combat endurance is important for managing the Chinese navy’s threat to Australia.

Functionally, Australia and Japan have distinct strengths, as well as vulnerabilities that the other can help mitigate. Japan faces challenges in cybersecurity and logistical sustainment, while Australia lacks integrated air and missile defence (IAMD) and efficient shipbuilding.

Fortunately, Japan has a strong foundation in IAMD and shipbuilding, while Australia excels in cybersecurity and benefits from a geographically resilient logistical basis. By addressing each other’s weaknesses through increased bilateral exercises, common equipment and systems, and joint defence industry investments, Japan and Australia can build a more resilient defence posture.

Japan-Australia defence complementarity is already taking shape to some degree. Geographic cooperation has been an indirect but longstanding feature for both nations due to US naval strategy since the early Cold War. Functional cooperation has advanced further in recent years. At the Trilateral Defence Ministers’ Meeting in November 2024, Australia, Japan and the US discussed cooperation on IAMD systems. Shipbuilding collaboration will likely begin if Australia chooses a design based on the Japanese New FFM class for its new general-purpose frigates. Cybersecurity cooperation is also advancing through joint exercises between Australia, Japan and the US.

Japan’s ability to sustain a protracted conflict remains a challenge, as its shipyards and ammunition factories are in range of China’s missiles and can be easily targeted. For both nations to make credible contributions to regional deterrence, robust defence-industrial cooperation must be a foundation of effective contingency and operational planning. Beyond shipbuilding, the two countries should look to collaboration on ammunition production to reinforce war endurance capability. They should also consider storing mothballed assets in Australia, such as aircraft that have been retired but are still worth keeping for a while, in case they’re needed.

Deeper ties will need dedicated advocates. Both countries’ strategic communities must define the desired end-state of cooperation and identify opportunities that advance this goal.

Security cooperation steps up with Japanese F-35 access to Australia

The development in August last year attracted little attention, but it represented a significant step forward in the strategic relationship between Japan and Australia. For the first time, the Japan Air Self-Defense Force deployed two F-35 fighters overseas—and it chose to send them to Australia.

The reason for the aircraft deploying to the Royal Australian Air Force’s Tindal base in the Northern Territory was not to exercise there. Rather, their flight to the base was itself an exercise, to pave the way for Japanese F-35s to go to Australia in future. Those later deployments will support joint training that will deepen the relationship between Japanese and Australian forces.

An ability to shift F-35s to Australia may be valuable in wartime, too.

The two countries have been working up to this level of cooperation for more than a decade. In 2007 they signed the Japan-Australia Joint Declaration on Security Cooperation. Since 2014 they have strengthened their relationship under the Special Strategic Partnership, under which they work together on economic and security affairs and on regional peace and stability. Then in 2022 the Japan-Australia Joint Declaration on Security Cooperation was updated to enhance their security connection.

Also in 2022, the two countries signed the Japan-Australia Reciprocal Access Agreement (RAA), which aimed at facilitating visits by the forces of each of them to the other. The F-35 deployment to RAAF Tindal was the first application of that agreement. The aircraft, from Misawa Air Base’s 301st Squadron, flew 6400km to Tindal via the US Air Force’s Andersen base on Guam. JASDF tankers repeatedly refueled them in flight.

Future participation in exercises in Australia by Japanese F-35s and their crews will promote the ability of the two countries’ forces to operate together. That will extend to operating with other like-minded Indo-Pacific countries when Japanese F-35 units participate in multinational exercises in Australia. In 2022 JASDF F-2 fighters and their crews participated in the RAAF’s big multinational Exercise Pitch Black. F-35s, which will become the mainstay of the JASDF fighter squadrons, can now follow, their crews getting the particular opportunity to work with other operators of the type.

Another special opportunity for Japan is access to vast air space in northern Australia for training, including the Delamere Weapons Range of more than 2000 square kilometres.

An acquisition and cross-servicing agreement between Australia and Japan provides for logistical backing for the F-35s of both countries. And an F-35 maintenance centre at RAAF Williamtown in New South Wales will be able to support Japan’s aircraft of the type when they are deployed to Australia.

A further advantage of access to Australia by Japan is opportunity for dispersion. China can attack airfields within thousands of kilometres of its territory with cruise and ballistic missiles. Conceivably, Japanese air bases and even civil airports would be wrecked in wartime, forcing JASDF units to seek refuge elsewhere.

Guam is an unlikely destination for them, since it also would be a target for Chinese strike missiles. Australian bases, on the other hand, are at safer distances from China—though it must be acknowledged that they are much too far away for maintaining fighter operations in North Asia.

Japan-Australia security cooperation has progressed to the stage of quasi-alliance. For Japan’s forces, formerly accustomed to cooperating little with any country except the US, the relationship with Australia is opening new opportunities.

Security cooperation steps up with Japanese F-35 access to Australia

The development in August last year attracted little attention, but it represented a significant step forward in the strategic relationship between Japan and Australia. For the first time, the Japan Air Self-Defense Force deployed two F-35 fighters overseas—and it chose to send them to Australia.

The reason for the aircraft deploying to the Royal Australian Air Force’s Tindal base in the Northern Territory was not to exercise there. Rather, their flight to the base was itself an exercise, to pave the way for Japanese F-35s to go to Australia in future. Those later deployments will support joint training that will deepen the relationship between Japanese and Australian forces.

An ability to shift F-35s to Australia may be valuable in wartime, too.

The two countries have been working up to this level of cooperation for more than a decade. In 2007 they signed the Japan-Australia Joint Declaration on Security Cooperation. Since 2014 they have strengthened their relationship under the Special Strategic Partnership, under which they work together on economic and security affairs and on regional peace and stability. Then in 2022 the Japan-Australia Joint Declaration on Security Cooperation was updated to enhance their security connection.

Also in 2022, the two countries signed the Japan-Australia Reciprocal Access Agreement (RAA), which aimed at facilitating visits by the forces of each of them to the other. The F-35 deployment to RAAF Tindal was the first application of that agreement. The aircraft, from Misawa Air Base’s 301st Squadron, flew 6400km to Tindal via the US Air Force’s Andersen base on Guam. JASDF tankers repeatedly refueled them in flight.

Future participation in exercises in Australia by Japanese F-35s and their crews will promote the ability of the two countries’ forces to operate together. That will extend to operating with other like-minded Indo-Pacific countries when Japanese F-35 units participate in multinational exercises in Australia. In 2022 JASDF F-2 fighters and their crews participated in the RAAF’s big multinational Exercise Pitch Black. F-35s, which will become the mainstay of the JASDF fighter squadrons, can now follow, their crews getting the particular opportunity to work with other operators of the type.

Another special opportunity for Japan is access to vast air space in northern Australia for training, including the Delamere Weapons Range of more than 2000 square kilometres.

An acquisition and cross-servicing agreement between Australia and Japan provides for logistical backing for the F-35s of both countries. And an F-35 maintenance centre at RAAF Williamtown in New South Wales will be able to support Japan’s aircraft of the type when they are deployed to Australia.

A further advantage of access to Australia by Japan is opportunity for dispersion. China can attack airfields within thousands of kilometres of its territory with cruise and ballistic missiles. Conceivably, Japanese air bases and even civil airports would be wrecked in wartime, forcing JASDF units to seek refuge elsewhere.

Guam is an unlikely destination for them, since it also would be a target for Chinese strike missiles. Australian bases, on the other hand, are at safer distances from China—though it must be acknowledged that they are much too far away for maintaining fighter operations in North Asia.

Japan-Australia security cooperation has progressed to the stage of quasi-alliance. For Japan’s forces, formerly accustomed to cooperating little with any country except the US, the relationship with Australia is opening new opportunities.

Is Australia-Japan defence cooperation about to be throttled up?

Defence cooperation between Australia and Japan has yet to find its top gear but, after a cautious start, that relationship is in pole position among Australia’s regional security partnerships. The road ahead may soon lead into new and productive areas of cooperation though this is also likely to test comfort levels and appetite for risk to a sharper degree than before.

Bilateral interaction between the two countries’ armed forces has visibly picked up over the past year. The deployment of several Japan Air Self Defense Force F-35A joint strike fighters to RAAF Base Tindal, last August, was a prominent milestone, officially inaugurating the reciprocal access agreement (RAA), almost a decade after both countries agreed to negotiate one. A reciprocal deployment of RAAF F-35As to Japan, for Exercise Bushido Guardian, followed in September. In December, 230 Australian Army personnel took part in a command post exercise, Yama Sakura, for the first time, with US troops and Japan self defense ground Forces. And in February, ADF personnel deployed to Japan and Hawaii for Exercise Keen Edge 24.

It is still relatively uncommon for the JSDF to conduct drills with non-US forces in Japan so ADF involvement in these exercises reflects Tokyo’s growing comfort with Australia as a defence partner.

Despite this intensification of activity, some frustration remains on the Australian side that the RAA is performing short of expectations. But the RAA does not regulate all military activity, and some continues to occur on an ad hoc basis. For decades, Australia has already had access to seven military bases in Japan, under a status of forces agreement tied to UN Command Forces Rear, headed by a RAAF officer, based at Yokota Air Base. This remains in play alongside the bilateral RAA for Australian defence activities specifically relating to Korean Peninsula security.

Perhaps the most telling feature of the bilateral defence relationship in this growth phase is that Japan now frequently takes the initiative in defence cooperation. This has included a willingness to discuss sensitive Taiwan scenarios that has sometimes challenged Australian comfort levels. The establishment of a genuine reciprocity among close partners tied to a common ally, in the US is a positive trend.

Cooperation could soon expand into wider areas of defence, testing integration between their wider industrial eco-systems. First, in the independent review into Australia’s surface naval capability, Japan’s Mogami 30FFM multi-mission frigate, built by Mitsubishi Heavy Industries, was identified as a potential off-the-shelf fit for the replacement to the ANZAC-class. If Japan joins the fray by bidding to supply Australia with 11 future general-purpose frigates, the first three of which are to be built overseas and the remainder at Henderson in Western Australia, this could add extra ballast to the bilateral partnership in the form of a large-scale defence industrial collaboration.

Second, in a move that few observers foresaw, Japan could be officially invited by the AUKUS partners to participate in Pillar 2 as soon as April. Either of these possibilities would bring a new dimension to the strategic partnership between Canberra and Tokyo. Both also come with significant risks attached, requiring close political handling, clear communication and mutual expectation management.

There is a strong feeling of déjà vu about the future frigate decision, recalling the outcome of the ill-fated SEA1000 decision, in April 2016. This saw Japan crashing unceremoniously out of Australia’s future submarine competition in circumstances that were unnecessarily humiliating. Prime Minister Tony Abbott had initially encouraged Tokyo to bid on broader strategic grounds, only for the government of his successor, Malcolm Turnbull, to opt for a French design over the Japanese (and German) offerings, on capability grounds. An important lesson from this diplomatic debacle was Australia’s error in sending mixed signals about the criteria for selecting the future submarine. The bilateral defence partnership eventually bounced back, but it was a jarring introduction for Japan to the Australian acquisition process.

Tokyo is likely to be wary about exposing itself to another potential bruising loss of face. The Mogami design probably has a better technical prospect of success than some of its potential competitors, from Germany, South Korea and Spain, but Japan’s defence industry still falls behind on export experience and market savvy. Even a successful bid would be likely to strain relations, given Canberra’s expectations for delivering capability on a tight timescale and workforce strains in Western Australia. Those in charge of the frigate acquisition process should keep this context front of mind, and make deliberate efforts to be transparent and consistent with Tokyo in regard to the requirements and selection criteria. Appeals to the ‘strategic’ logic of choosing a Japanese design are otherwise likely to fall on deaf ears in Tokyo.

The parallel prospect of Japan’s participation in AUKUS Pillar 2, as a ‘plus’ partner, is not a bilateral defence issue per se, but could also change the dynamics of the defence relationship. During Deputy Prime Minister Richard Marles’s latest trip to Japan he made encouraging noises about the potential for partnering with Japan on Pillar 2 technologies. But a closer reading of his comments suggests that Canberra remains cautious, alive to the risks of diluting the AUKUS partnership before it has begun to deliver submarine capability under Pillar I.

It now appears that Washington is intent on bringing Japan into Pillar 2 sooner rather than later, over any Australian and British qualms. An announcement about Japan’s inclusion could be made when Prime Minister Kishida visits Washington next month. There could be different motivations for this move, including the Biden administration’s cautionary desire to tightly bind its intra-alliance initiatives ahead of a possible change of US government. And Japan’s boost to defence spending under Kishida and its advanced technological base could invigorate AUKUS Pillar 2. However, Japan’s inclusion would also be bound to complicate AUKUS in process terms, while its ability to safeguard sensitive information still falls far short of the Five Eyes intelligence sharing arrangement’s standards, though it is improving.

Canberra’s overriding priority remains the delivery of submarine capability under AUKUS Pillar 1. But given that Washington now appears determined to press ahead on Japan’s Pillar 2 invitation, Australia should probably just accept this as a fait accompli and try to shape the terms of Japan’s partnership, rather than wasting energy opposing it. Notably, in January, Australia’s Department of Defence publicly announced a research agreement with Japan to enhance strategic capabilities in robotic and autonomous systems for undersea warfare. The overlap with an AUKUS Pillar 2 designated workstream, one that also directly complements Pillar 1, seems to hint at a pragmatic Australian hedge towards Japan’s eventual inclusion.

Is Australia-Japan defence cooperation about to be throttled up?

Defence cooperation between Australia and Japan has yet to find its top gear but, after a cautious start, that relationship is in pole position among Australia’s regional security partnerships. The road ahead may soon lead into new and productive areas of cooperation though this is also likely to test comfort levels and appetite for risk to a sharper degree than before.

Bilateral interaction between the two countries’ armed forces has visibly picked up over the past year. The deployment of several Japan Air Self Defense Force F-35A joint strike fighters to RAAF Base Tindal, last August, was a prominent milestone, officially inaugurating the reciprocal access agreement (RAA), almost a decade after both countries agreed to negotiate one. A reciprocal deployment of RAAF F-35As to Japan, for Exercise Bushido Guardian, followed in September. In December, 230 Australian Army personnel took part in a command post exercise, Yama Sakura, for the first time, with US troops and Japan self defense ground Forces. And in February, ADF personnel deployed to Japan and Hawaii for Exercise Keen Edge 24.

It is still relatively uncommon for the JSDF to conduct drills with non-US forces in Japan so ADF involvement in these exercises reflects Tokyo’s growing comfort with Australia as a defence partner.

Despite this intensification of activity, some frustration remains on the Australian side that the RAA is performing short of expectations. But the RAA does not regulate all military activity, and some continues to occur on an ad hoc basis. For decades, Australia has already had access to seven military bases in Japan, under a status of forces agreement tied to UN Command Forces Rear, headed by a RAAF officer, based at Yokota Air Base. This remains in play alongside the bilateral RAA for Australian defence activities specifically relating to Korean Peninsula security.

Perhaps the most telling feature of the bilateral defence relationship in this growth phase is that Japan now frequently takes the initiative in defence cooperation. This has included a willingness to discuss sensitive Taiwan scenarios that has sometimes challenged Australian comfort levels. The establishment of a genuine reciprocity among close partners tied to a common ally, in the US is a positive trend.

Cooperation could soon expand into wider areas of defence, testing integration between their wider industrial eco-systems. First, in the independent review into Australia’s surface naval capability, Japan’s Mogami 30FFM multi-mission frigate, built by Mitsubishi Heavy Industries, was identified as a potential off-the-shelf fit for the replacement to the ANZAC-class. If Japan joins the fray by bidding to supply Australia with 11 future general-purpose frigates, the first three of which are to be built overseas and the remainder at Henderson in Western Australia, this could add extra ballast to the bilateral partnership in the form of a large-scale defence industrial collaboration.

Second, in a move that few observers foresaw, Japan could be officially invited by the AUKUS partners to participate in Pillar 2 as soon as April. Either of these possibilities would bring a new dimension to the strategic partnership between Canberra and Tokyo. Both also come with significant risks attached, requiring close political handling, clear communication and mutual expectation management.

There is a strong feeling of déjà vu about the future frigate decision, recalling the outcome of the ill-fated SEA1000 decision, in April 2016. This saw Japan crashing unceremoniously out of Australia’s future submarine competition in circumstances that were unnecessarily humiliating. Prime Minister Tony Abbott had initially encouraged Tokyo to bid on broader strategic grounds, only for the government of his successor, Malcolm Turnbull, to opt for a French design over the Japanese (and German) offerings, on capability grounds. An important lesson from this diplomatic debacle was Australia’s error in sending mixed signals about the criteria for selecting the future submarine. The bilateral defence partnership eventually bounced back, but it was a jarring introduction for Japan to the Australian acquisition process.

Tokyo is likely to be wary about exposing itself to another potential bruising loss of face. The Mogami design probably has a better technical prospect of success than some of its potential competitors, from Germany, South Korea and Spain, but Japan’s defence industry still falls behind on export experience and market savvy. Even a successful bid would be likely to strain relations, given Canberra’s expectations for delivering capability on a tight timescale and workforce strains in Western Australia. Those in charge of the frigate acquisition process should keep this context front of mind, and make deliberate efforts to be transparent and consistent with Tokyo in regard to the requirements and selection criteria. Appeals to the ‘strategic’ logic of choosing a Japanese design are otherwise likely to fall on deaf ears in Tokyo.

The parallel prospect of Japan’s participation in AUKUS Pillar 2, as a ‘plus’ partner, is not a bilateral defence issue per se, but could also change the dynamics of the defence relationship. During Deputy Prime Minister Richard Marles’s latest trip to Japan he made encouraging noises about the potential for partnering with Japan on Pillar 2 technologies. But a closer reading of his comments suggests that Canberra remains cautious, alive to the risks of diluting the AUKUS partnership before it has begun to deliver submarine capability under Pillar I.

It now appears that Washington is intent on bringing Japan into Pillar 2 sooner rather than later, over any Australian and British qualms. An announcement about Japan’s inclusion could be made when Prime Minister Kishida visits Washington next month. There could be different motivations for this move, including the Biden administration’s cautionary desire to tightly bind its intra-alliance initiatives ahead of a possible change of US government. And Japan’s boost to defence spending under Kishida and its advanced technological base could invigorate AUKUS Pillar 2. However, Japan’s inclusion would also be bound to complicate AUKUS in process terms, while its ability to safeguard sensitive information still falls far short of the Five Eyes intelligence sharing arrangement’s standards, though it is improving.

Canberra’s overriding priority remains the delivery of submarine capability under AUKUS Pillar 1. But given that Washington now appears determined to press ahead on Japan’s Pillar 2 invitation, Australia should probably just accept this as a fait accompli and try to shape the terms of Japan’s partnership, rather than wasting energy opposing it. Notably, in January, Australia’s Department of Defence publicly announced a research agreement with Japan to enhance strategic capabilities in robotic and autonomous systems for undersea warfare. The overlap with an AUKUS Pillar 2 designated workstream, one that also directly complements Pillar 1, seems to hint at a pragmatic Australian hedge towards Japan’s eventual inclusion.

How Japan could quickly build up its submarine force

Japan can quickly and inexpensively increase its force of diesel-electric combat submarines from 22 to at least 28, if it stops prematurely retiring them.

That would provide more of the one category of warship that the armed forces of democratic countries could safely operate close to China in wartime. Moreover, additional Japanese submarines would ease pressure on the US Navy, which is straining to maintain submarine numbers.

Last month Japan decommissioned the first of its 11 Oyashio class boats. They are contemporaries of Australia’s Collins class, which Canberra is not remotely close to withdrawing from service.

JS Oyashio was 25 years old and was only 17 when pulled from the combat force to be converted into a training submarine. Most navies would regard that as waste, just as most air forces would not follow Japan’s policy of discarding F-15 fighters that are nowhere near worn out.

Japan’s early decommissioning of submarines seems especially improvident given the importance of its boats in helping to deter a Chinese attack on Taiwan. They are based near China and are operated by people highly experienced in the waters that would be the main naval theatre in such a conflict.

Consider, for example, the results of table-top simulations of a Taiwanese war published by the Center for Strategic and International Studies in Washington in January. After Japan’s forces in the games suffered initial blows, the researchers reported that: ‘most valuable were the Japanese submarines, which could strike Chinese amphibious ships and the Chinese picket line around Taiwan.’

For decades, Japan has almost always built a submarine a year. The current and planned fleet is 22 plus two: 22 for operations, including one routinely assigned to development work but presumably fully armed, and two converted for training. On average, they’ll be retiring after about 24 years in service.

Elsewhere, submarine service lives of 30 years are unremarkable.

If Japan suspended submarine retirements for six years and raised the average decommissioning age to 30, it would increase its fleet by six boats without having to spend even one more yen on construction. It could enlarge the fleet at a rate of one a year.

Using each submarine for 32 years would enlarge the fleet by eight. The US Navy has found that its Los Angeles class nuclear submarines are good for 36 years.

The idea of keeping Japanese submarines going for longer is not new. US Congressional Research Service analyst Ronald O’Rourke said in 2020 that the number-one opportunity to expand the naval power of the US and its allies was by enlarging Japan’s submarine force. And in 2021 I proposed that, since Japan planned to throw away Oyashios before they were worn out, they’d make fine temporary additions to the Royal Australian Navy while it awaited delivery of nuclear submarines.

Keeping the remaining Oyashios in Japanese service would be much more valuable.

Japan has expanded its fleet once before by lengthening service lives. The fleet target of 22 plus two, achieved last year, was set in 2010 when Japan had 18 boats (16 plus two) and retired them generally before they got to even 20 years.

Another immediate opportunity is for Japan to end its practice of dedicating two submarines to training. A Japanese naval source says that converting a boat for that purpose every few years involves removing combat equipment, much reducing its war-fighting capability.

Other navies teach sailors the ropes in front-line submarines. If Japan did that, it could add two submarines to its combat force without lifting the building rate.

So, a quick addition of 10 submarines to the Japan Maritime Self-Defense Force is quite conceivable.

Japan would have to train enough people for one extra crew each year, though that should not be difficult. It was doing that several years ago as it lifted the force to 22 plus two.

It would also need expanded maintenance capacity, additional weapons such as torpedoes, and a larger budget to cover running costs.

But the biggest additional financial burden may be in shipyard work.

The 2010 decision to operate the submarines for longer required life-extending overhauls for the Oyashios, which began in 2013 and were followed by modernisation to almost the standard of the succeeding Soryu class, according to Japan’s government. If Japan lifts the submarine retirement age to 30 or 32, its submarines will presumably need more or deeper overhauls and modernisation.

That would cost much less than new submarines.

But, however well modernised, will diesel-electric submarines continue to be useful?

Peter Dutton, who was defence minister when Australia decided in 2021 it needed nuclear-powered submarines, wrote last year that the advice from our experts was clear. Diesel-electric submarines would not be able to compete in hostilities in the South China Sea beyond 2035. The diesel-electric submarine needs to come up near to the surface to ‘snort’—raising a snorkel to run its diesel engines and recharge its batteries—and would be detected by emerging radar technologies, Dutton said.

That assessment should not discourage Japan from extending the service lives of its diesel-electric submarines. That would yield a larger Japanese fleet well before 2035, which cannot be regarded as a sharp turning point at which the conventionally powered submarine concept will suddenly become obsolete. Such changes come gradually.

Also, Japanese submarines would operate in wartime not so much in the South China Sea, where the presence of Chinese airborne radar surveillance might be uncontested, but mainly in the East China Sea and nearby waters, close to Japanese and Taiwanese air bases.

And all Japanese submarines delivered since 2009 (after the Oyashio class) have either air-independent propulsion systems or large-capacity lithium-ion batteries enabling them to ‘loiter’. Both technologies allow a commander to reduce or entirely avoid snorting in dangerous locations. Australia’s previously planned diesel-electric submarines lacked such features.

Although Japan plans to double its defence share of GDP to 2% by 2027, a force structure plan issued in December confirmed that the 22-plus-two submarine fleet size would stay.

Why the government and navy rejected the possibility of further expansion is unclear. Possible explanations include competition within the navy for funds or a simply a disinclination to accept the disruption of expansion beyond the 2010 plan.

Whatever the reason, perhaps the one influence that can change minds in Tokyo is Japan’s US ally. If Washington, in seeking to deter China, values undersea strength as highly as it seems to, it needs to tell Japan to stop throwing away good submarines.