Defence Japan mulls nuclear submarines after U.S. clears South Korea

Last Thursday, Defence Minister Koizumi Shinjiro said that Japan might need to consider introducing nuclear-powered submarines, following U.S. President Donald Trump's recent decision to allow South Korea to build its own. Speaking on a programme aired by TBS, Koizumi remarked that Japan's security environment had become so severe that it was time to discuss whether to continue relying on diesel-powered submarines or to shift toward nuclear propulsion.



The discussion gained urgency after a summit between the United States and South Korea on 29 October, during which South Korean President Lee Jae-myung asked Washington to approve the supply of fuel for nuclear submarines, arguing that it was necessary to counter growing threats from China and North Korea. The next day, Trump announced on his social media platform that he had approved Seoul's plans. In East Asia, China already operates nuclear-powered submarines, while North Korea has made its development a key part of its five-year military strategy announced in 2021. Commenting on these developments, Koizumi noted that South Korea's move marked a significant shift, pointing out that all the countries surrounding Japan now possess or are pursuing such vessels.

Japan and South Korea possess only diesel submarines and have relied on the U.S. for nuclear submarines to counter China and Russia. The operational details of U.S. submarines are secret, but they are believed to be deployed throughout the Pacific region. Nuclear submarines are capable of extended, long-distance operations, but they cost far more to build than their diesel counterparts. There is debate in Seoul about whether South Korea needs such capabilities in the relatively confined waters around the country. They could be deployed in the Pacific Ocean and take part in joint operations with the U.S. Among Pacific Rim countries, Australia is planning to acquire its first nuclear-powered submarines as part of the AUKUS partnership with the U.S. and the U.K.

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Paywall alert:

I'm a bit surprised that South Korea, Japan, and Australia didn't already have nuclear subs.

Going by news reports, Japan's non-nuclear subs are supposed to be really good. Also, Japan/Korea/Australia are focused on regional defense (like their own country from adjacent ones), not on the imperialistic reach that nuke power allows.

Konnichiwa Mina-san!

Nuclear submarines are always making noise. This makes them less stealthy than diesel submarines. Noise is a major drawback in submarine combat.

Japan's Self-Defense Forces are exclusively defensive. Instead of going to an enemy country and attacking, they quietly wait for the enemy to come and then attack.

For this reason, silent diesel submarines are more suitable for Japan's defense than nuclear submarines, which are capable of long-distance voyages. Because Japanese submarines are always submerged in the waters near Japan, waiting for the enemy.

On the other hand, since South Korea shares the peninsula with its enemy, North Korea, air and ground combat will naturally be the focus, and submarines cannot be expected to play an active role.

Nevertheless, they want nuclear submarines to enable longer voyages...

South Korea's exclusive economic zone(EEZ) is only one-tenth the size of Japan's and one-twentieth the size of Australia's. Which country are they going to fight against?

NANGI

NANGI said:

South Korea's exclusive economic zone(EEZ) is only one-tenth the size of Japan's and one-twentieth the size of Australia's. Which country are they going to fight against?

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Or be selling them to? I haven't come across anything specifically about subs, but there've been some recent complaints about US ship-building capabilities/capacity.

I didn't read the details and thought the US was going to have South Korea build nuke subs for the US. I just reread it and it seems Trump wants South Korea to have it's own nuke subs. I guess the US will help them build them and provide some of the fuel they need. It's supposed to be a deterrent to China & North Korea.

If this 'permission to build' was being done by a normal US administration, I'd wonder if it was a chip on the chessboard--letting korea, in the face of dprk and maybe china, move closer to nuclear weapons without actually having them (so no issues with the NPT).

It may have a similar ring as what has happened in japan. Takaichi welcoming the guy from taiwan, and kind of at the same time saying problems in taiwan would probably merit some reaction from japan's self defense forces.

If it did act to defend/help taiwan, I'm sure the US would like to quickly use (or have available) any/all of its military assets in korea to do that, probably pulling korea into it. And if korea could field subs, even if not directly involved, it'd be more noise/targets out there for the chinese to deal with. And the thinking might go that if there are more subs out there, with the chinese likely unable to discriminate which are US, or korean, or japanese, they might be more cautious about taking any action.

blah, blah, blah...

Konnichiwa Mina-san!

Alignment of interests

The United States can sell expensive nuclear submarines to South Korea, and South Korea can possess nuclear submarines, a long-cherished dream since the 1990s. The interests of both countries are aligned.


The couple lived together but thought differently.

However, the United States insists on domestic manufacturing in order to revive its domestic shipbuilding industry. Furthermore, if a nuclear submarine is manufactured in South Korea, there will always be attempts to open the black box and steal the technology, so manufacturing in South Korea is unacceptable.

Conversely, South Korea wants to steal nuclear submarine construction technology by manufacturing them in South Korea. In fact, diesel submarines were also made possible by stealing German technology. South Korea and Germany are now rivals when it comes to selling diesel submarines overseas.

Next, South Korea will probably want to sell nuclear submarines. To achieve this, manufacturing within Korea is essential. But President Trump won't allow that.


A capable enemy is better than an incapable friend.

President Trump is trying to reduce the number of U.S. troops deployed overseas and have other countries take over. In this regard, it would be desirable for South Korea's naval power to be strengthened. If there had been no Taiwan issue, South Korea would not have been allowed to possess nuclear submarines.

However, the South Korean military has become accustomed to leaking information to China and North Korea. And the United States is extremely afraid of highly classified information such as nuclear submarines being leaked.


Who's gonna have the last laugh?

The United States wants to sell expensive nuclear submarines and strengthen South Korea's naval power.

South Korea wants to strengthen its naval capabilities and potentially sell nuclear submarines in the future.

China and North Korea want South Korea to waste money on nuclear submarines. It would be even better if they could get information on nuclear submarines.


NANGI