• Satoru Nagao

Japan should lease nuclear submarines from the US

Updated: Nov 26, 2021

Photo Source: Japan Today

In September 2021, Australia, the US, and the UK published a joint statement of their cooperation as AUKUS, a new security alliance. Under this umbrella, the US and the UK will support Australia in acquiring eight nuclear submarines, making it easier for Australia to deploy them to the South Pacific, the South China Sea, and the Indian Ocean. In the Indo-Pacific, the US and India have nuclear submarines. France has also deployed a nuclear submarine in the South China Sea. In the wide sea of the Indo-Pacific, nuclear submarines are common weapons. However, there is one regional country that does not possess a nuclear submarine despite having 23 conventional submarines (including two for training): Japan. Is there a possibility that Japan will obtain a nuclear submarine? If so, what is the security need that it will be responding to? What is the potential problem with Japan’s possession of nuclear submarines and how could this be solved? This article will explain.

What are the security needs?

Recent situations require Japan’s Maritime Self Defense Force (JMSDF) to deploy in a wider area. Nuclear submarines offer an advantage because they can operate in a far wider area than conventional ones. The Maritime Self Defense Force has been expanding its area of activities, and its submarine recently called at a port in Vietnam. Japan’s submarines need the capability to deploy in the South China Sea. During the Cold War, submarines were the main weapon used to deal with the threat of the USSR. Japan possessed anti-submarine patrol planes and submarines to deter the activities of the USSR. From Vladivostok, the USSR deployed nuclear ballistic missile submarines in the Sea of Okhotsk and Japanese anti-submarine forces detected them. Even after the Cold War ended, Russian submarines have remained one of the main security concerns for Japan.

China's recent actions also demand that Japan deploy more submarines. In 2012, just before Shinzo Abe was sworn in as prime minister, he published short English article entitled, “Asia’s Democratic Security Diamond.” In this article, he pointed out, “The South China Sea seems set to become a ‘Lake Beijing,’ which analysts compared to what the Sea of Okhotsk was to Soviet Russia: for China, a sea deep enough for the People’s Liberation Army’s navy to base their nuclear-powered attack submarines, capable of launching missiles with nuclear warheads.” Because China cannot hide its nuclear missile submarines in places where other ships and planes are able to detect them, the US and its allies, including Japan, need to dispatch submarines in the South China Sea. The submarine forces of Japan are needed to deploy in a wider area from north to south. This provides a possible deterrence on Chinese aggressive actions in the disputed area, benefitting all states that have mutual interests in keeping the peace and stability of the region.

In addition, Japan’s Maritime Self Defense Force will need submarines for escorting its aircraft carrier battle groups. Recently, Japan’s helicopter carriers IZUMO and KAGA have called at ports in India and Sri Lanka and conducted annual joint exercises in the Indian Ocean. The IZUMO and KAGA destroyers are in the process of becoming aircraft carriers for F-35B stealth jets. As a test of this modification, US Marine F-35Bs have taken off from and landed on the IZUMO in this month. For these aircraft carriers, adversary submarines are the main threat. To deal with such submarines, Japan needs submarine escorts. However, conventional-powered submarines do not have enough power to do this. The maximum speed of Japan’s conventional submarines is under 20 knots, well below the 30-knot speed of the IZUMO and the KAGA. Another drawback of conventional submarines is that they need to surface for air sometimes. Nuclear-powered submarines are what is needed to escort Japan’s aircraft carrier battle groups.


There is no legal restriction—such as the "pacifist" constitution—in Japan possessing nuclear-powered submarines. In the past, Japan had a nuclear-powered ship called the MUTSU. However, when the MUTSU had an accident in 1974, a problem was revealed. Despite the accident being a very minor one, most ports in Japan refused it entry. Only the port of Sasebo allowed it to call. That incident proved that nuclear accidents are a very sensitive issue in Japan. If Japan started to develop its own nuclear submarines, minor accidents will be likely to occur in the process, posing a high risk to the project’s completion.

Way Forward

Therefore, if Japan decides to possess nuclear submarines, there must be no minor accidents. Is that really possible or realistic? India seems to have found a solution to this issue by leasing Russian submarines. Japan could do the same and lease a trustworthy nuclear submarine from the United States. All submarines the US has are nuclear-powered submarines, and some of them are operating from the Yokosuka base in Japan. And there have been few accidents in the past. Therefore, if Japan leases trustworthy US nuclear submarines, operates from the US base in Yokosuka (or Guam), and learns how to use them, it will have found the solution. In the absence of accidents, Japanese civilians and the international community will eventually come to accept nuclear submarines as major component of the JMSDF. If Japan wants to produce the submarines domestically, it can start once trust and safety has been guaranteed and demonstrated.


Dr. Satoru Nagao is a fellow (non-resident) at Hudson Institute, based in Tokyo, Japan. From December 2017 through November 2020, he was a visiting fellow at Hudson Institute, based in Washington, D.C.

This is an updated version of an article originally published in The Straits Times.

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