Australia may have a way of very cheaply and quickly expanding its submarine force, improving its defences this decade and preparing for its planned nuclear-powered boats.

We might do this by buying good second-hand submarines from Japan. The possibility would present some problems and could in fact be unworkable, but it offers such great potential advantages that we must look hard at whether it could be achieved.

It should not be summarily dismissed as unconventional and managerially complicated.

Australia’s first nuclear submarine won’t be ready until about 2040 if it’s built in Adelaide. By importing nuclear boats, that might be brought forward to 2031 ^[1] or even 2030 ^[2]. But that would still leave the submarine force at its current, inadequate level in the 2020s, which are looking increasingly dangerous.

We’ll also have the challenge of generating crews for the nuclear submarines, whenever they appear. The more submarines in service, even if they are diesel powered, the easier it will be to create crews.

One proposal that would address the training problem has been to buy new diesel submarines as stopgaps ^[3], ideally using a design based on the current Collins class.

This solution has three serious drawbacks. Even Collins derivatives probably couldn’t be delivered until the 2030s. Construction would be expensive and, for a small batch, highly uneconomical. And Australia would end up stuck with new submarines with a form of propulsion that it already regards as inadequate for the long term.

Second-hand Japanese submarines, by contrast, might be acquired very quickly and cheaply, and, having perhaps seven years of life left in them, wouldn’t hang around as doubtful assets into the 2060s.

The Japanese Maritime Self-Defense Force takes delivery of one submarine a year. For any other navy, that would imply a fleet of about 30 boats, since a submarine can typically serve for something like 30 years. But the force is not funded to operate so many and instead retires them early.

Until a few years ago, the fleet comprised 18 submarines. The number is now 23 and soon due to rise to 24, including two training boats.

The submarines we might lay our hands on are contemporaries of the Collins class, the Oyashio class ^[4], commissioned between 1998 and 2008.

Their surface displacement is 2,800 tonnes, compared with 3,100 tonnes for the Collins class. Their endurance and range are probably adequate for Australian missions. Their silencing and sensor performance are unlikely to be second-rate, but their crew size is largish at 70.

Oyashios in Australian service would be used closer to home than the long-range Collins class. They could cover the archipelagic straits of the approaches to our continent and help deal with targets that got through. All Collins boats would then be available for more distant missions.

Japan has already demoted the two oldest Oyashios to training roles, modifying them accordingly. Nine more remain in frontline service, still with full combat capability and each seemingly destined for retirement at age 23.

These include seven confirmed in 2018 as refitted to give them longer lives than originally planned and to bring them to almost the technology standard of the later Soryu class ^[5], itself once a candidate to replace the Collins boats. The other two front-line Oyashios have presumably been similarly refitted since then.

Since Japan’s submarine fleet still needs to expand by one, we should assume the country won’t decommission an Oyashio in 2022 as it takes delivery of a new vessel. Instead, the oldest frontline boat of the class, the Uzushio, may become available in 2023.

Australia could ask Japan for the Uzushio and the other eight frontline Oyashios as they leave service at yearly intervals. The purchase price shouldn’t be much above scrap value.

Japan would be delighted by the closer defence relationship, and it would get business in supporting the vessels.

Many countries operate high-quality second-hand warships, often bought from the US or UK. Australia has done so many times, and it has lately sold two capable upgraded frigates to Chile.

The Australian collection of Oyashio-class boats would reach seven in 2029 and remain at that level until 2031, assuming, roughly, that their age limit is 30. After that period, the number would decline by one a year—conveniently in step with a feasible schedule for arrival of imported nuclear boats. One in, one out.

Notice that with this proposal Australia could have 13 diesel submarines in service 25 years earlier than it was planning to have 12 under the cancelled Attack-class contract.

Mission availability of second-hand Oyashios might be better than that of the Collins class, because they would never go into the two-year major refits the Collins boats will undertake.

Supporting a completely unique class of vessels might look like an unattractive proposition, but it wouldn’t be impossible: the Collins-class boats are similarly full of systems and weapons not found elsewhere in the navy.

The support problem could be enormously reduced by relying as far as possible on Japan’s mature maintenance establishment for these submarines. Whenever necessary, they would be sent back to Japan for work. Keeping them in the hands of engineers and technicians who have long familiarity with them would greatly improve our confidence in prolonged operation.

Doing so should also be highly economical. Australia wouldn’t pay for plant and training to create elaborate domestic support infrastructure. For minor maintenance, Japanese shipbuilders and system suppliers could help by stationing people in Australia.

Japan would surely be a reliable partner for Australia in this. The two countries have the same strategic problem: China.

The big unknown in this proposal is how hard it would be to keep the Japanese submarines serving beyond 23 years.

Their physical condition upon retirement from the Japanese navy shouldn’t be a problem. Consider the Japanese reputation for excellent production and maintenance of physical articles. In 2016 then-ambassador Sumio Kusaka wrote ^[6] that, by applying the Japanese maintenance routine, Australia could operate Soryu-class submarines for ‘a long period of time’.

Still, the Oyashios’ current maintenance timetable is presumably phased so that each submarine is due for more work at the point of retirement. Each boat might therefore need a routine refit before commissioning into the Royal Australian Navy.

The potential showstopper is whether old electronics and software could be supported to age 30. That would depend in part on the depth of the modernisation the boats have had. Problems in this respect might be addressed with a little more updating, the cost of which should still make these submarines a bargain.

To get started with operations, we could ask Japan to lend a complete crew. Needing adequate English, these people would train Australians and gradually go home as the locals became familiar with how to operate the boats. Since the Japanese navy has so many submarines, it should be able to conjure up one more crew without too much difficulty.

Manuals would have to be translated to English, but display text of electronic systems would not, since such fiddling would be an unnecessary complication.

The idea of Australian sailors looking at, for example, combat-system menus written in Japanese may seem challenging, but members of armed services all over the world have to learn enough English to operate imported equipment. There’s no reason why Australian sailors shouldn’t be able to learn a little Japanese.

With Oyashios arriving annually from 2023, time available for training would be short. But the delivery timeframe is so attractively quick that slowish achievement of operational capability would be acceptable.

The government should urgently examine this possibility. And it should insist that the navy and Department of Defence look not just for problems in operating second-hand Japanese submarines but also for solutions.