The Biggest Reason Why Japan Cannot Go Nuclear

There are strong arguments for South Korea to attain nuclear weapons in the face of growing threats posed by North Korea’s unstoppable nuclear and missile development. Indeed, now over 76 percent of South Koreans support the idea of arming their country with its own nuclear weapons, according to a Gallup Korea poll announced in late January.

What about Japan? Some analysts suggest that South Korea going nuclear would incentivize Tokyo to follow suit. Is there any possibility of a nuclear domino effect extending from North Korea to South Korea to Japan?

The answer is definitely no.

Many experts, especially foreign ones, argue that the main reasons why Japan cannot obtain nuclear weapons are as follows.

First, as the only country to have suffered from the use of nuclear weapons in war, the public doesn’t want to go nuclear. Reflecting their “nuclear allergy,” 61 percent of respondents said in an opinion survey conducted last year that Japan should join the Treaty on the Prohibition of Nuclear Weapons, which came into force in January 2021. Japan has not yet ratified the treaty.

Second, the Japanese government lacks the financial resources needed for nuclear development.

Third, the impact on its international relations would be quite explosive, especially with the United States opposing South Korea’s nuclear armament, let alone Japan’s.

But in my view, the number one reason is different: Japan cannot find any location for nuclear tests. There is no space left for nuclear experiments in Japan.

Although this is little known among foreign observers, former Prime Minister Nakasone Yasuhiro ordered officials and experts to secretly investigate the possibility of Japan’s nuclear armament in 1970, when he was director-general of the Defense Agency. He revealed this episode in his memoir titled “Jiseiroku: rekishihotei no hikoku toshite” in Japanese (meaning “Self-reflection: as a Defendant at the Historical Court”). This book was published in 2004.

Nakasone said in the memoir that the conclusion of the investigation was that it is technically possible for Japan to be armed with nuclear weapons, and that it could be done within five years at a cost of 200 billion yen at that time.

But he also said it is impossible because Japan is too small to have a nuclear test site.

Japan is a densely populated nation, ranking 12th for the number of people per square kilometer of land among countries with a population of 10 million or more.

It is true that North Korea is smaller than Japan, but there is no freedom of speech there, so there is no way for North Korean residents to protest nuclear tests. In a democratic country like Japan forcing a nuclear test in a community would provoke huge demonstrations that would soon overthrow any administration. Another major reason why North Korea is able to continue its nuclear development despite U.N. sanctions is that it has abundant uranium resources. Since there is no need for North Korea to import nuclear material, it cannot be blocked by U.N. sanctions, Japan would face different difficulties in acquiring nuclear material.

It is true that Japan has the sixth-largest exclusive economic zone (EEZ) in the world. But a large-scale nuclear test could shatter small islands such as Okinotorishima or the Senkaku Islands. Japan’s precious fishing grounds could be ruined.

If the United States would lend the Nevada Desert to Japan, then Tokyo could conduct nuclear tests. But that will never happen.

In Japan, it has been confirmed that secret research on nuclear armament was conducted within the Defense Agency in 1994 – after the end of the Cold War. These independent surveys were repeatedly conducted in secret, as the agency sought to evade a harsh backlash as an atomic bombed country where public opinion strongly opposes nuclear armaments. The conclusion of those investigations was that Japan cannot have nuclear weapons.

Then, what can Japan do to cope with a worsening security environment in which Russia and North Korea are issuing direct threats to use tactical nuclear weapons and China expanding its nuclear arsenal?

On February 15, former Liberal Democratic Party Secretary-General Ishiba Shigeru asked Prime Minister Kishida Fumio at a House of Representatives Budget Committee meeting about nuclear sharing, in which Japan would be involved in decisions regarding the deployment and use of U.S. nuclear weapons in Japan.

Ishiba pointed out, “Nuclear sharing is possible. It even doesn’t violate the Three Non-Nuclear Principles,” in which Japan pledged not to manufacture, possess, or permit the introduction of nuclear weapons onto Japanese soil.

However, Kishida flatly rejected the idea, replying that nuclear sharing “is unacceptable given our country’s relevance to the legal system such as the Three Non-Nuclear Principles, and the government is not considering discussing it.”

Kishida, elected from a Hiroshima constituency, has actively advocated for nuclear disarmament to realize a “world without nuclear weapons.”

That said, Japan's only realistic policy is to continue to rely on the United States’ “nuclear umbrella” of deterrence.