Will Japan Acquire Nuclear Weapons?

The question of whether Japan should acquire nuclear weapons has been around for a surprisingly long time. Among the first to take up the subject were Tohoku University’s Hikosaka Tadayoshi in 1934 and, in 1940, Yoshio Nishina of the Riken Institute for Physical and Chemical Research. That year, Nishina became the first to alert the Japanese army to the possibility of nuclear explosives.

And then there was the hapless Professor Yoshitaka Mimura of Hiroshima’s Bunri University. In August 1945, Mimura lectured on the subject of nuclear fission at a seminar for Japanese army officers. “A nuclear bomb could be even smaller than a piece of caramel candy,” he told them, “but if it exploded at 200 metres above a populated city, it could destroy 200,000 lives.” A colonel had a question: “When can we have that bomb?” The professor’s response: “It’s difficult to say, but I can tell you this much: not before the end of this war.” Some twenty hours later, Mimura was standing on a Hiroshima neighbour’s porch when a massive shock wave lifted the professor off the floor and hurled him inside the house. It was 8.15 a.m. on August 6.

The Riken Institute’s scientists were then on the trail of nuclear fission, but they had been unable to make sufficient progress to please the colonel. The enemy had beaten the Japanese to that awesome rendezvous.

Some seventy-two years later, other regional powers sport nuclear arsenals—Russia, China, Pakistan, India and North Korea. Japan (or so Tokyo’s existing anti-nuclear policies would imply) still lags in nuclear weapons development. However, the newly re-elected government of Shinzo Abe has announced its determination to change a constitution that limits war-making abilities. Now under way is a national debate as vigorous as that of the early 1970s, when Japan’s growing Self-Defense Forces (Japan’s officialdom uses US spelling) were beginning to worry Japan’s neighbours. At that time, Japan’s foreign ministry offered this foreign correspondent an extraordinary open-door invitation: Visit any military base, interview any personnel and ask any question. As a result I gained some unusual insights into Japan’s evolving defence and nuclear policies.

This essay appears in the most recent Quadrant.
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Despite what is often called Japan’s “nuclear allergy”, some prominent Japanese person speaks from time to time in favour of having the nation join the nuclear club. One of the most recently outspoken has been Tadae Takubo, Kyorin University’s emeritus professor of international politics: “Japan must start saying right now that it might go nuclear. Forsaking nuclear weapons is like taking part in a boxing match and promising not to throw hooks.”

Discussion of the possibility of Japan’s acquiring nuclear weapons has followed recent aggressive activity by North Korea—a test on September 3 of what could be a hydrogen bomb and the North’s hurling of a possible intercontinental ballistic missile over Japan into the Pacific. All this has been accompanied by the Trump administration’s declaration that it is ending America’s long-held policy of “strategic patience”, the willingness to wait until Pyongyang for whatever reason—reappraisal or overthrow of the country’s peculiar Kim dynasty—elects to denuclearise.

Japan’s ability to wage war has been limited by its post-war constitution, which came into effect in 1947. To the Japanese much of this document reads like a translation—as, indeed, much of it is, with aides of the Allied Occupation’s Supreme Commander Douglas MacArthur shepherding it—at times sternly—through the Diet. Its most striking and controversial passage is Article 9, which states that “land, sea and air forces, as well as other war potential, will never be maintained”. That has been modified since, with land, sea and air Self-Defense Forces created, and in 2014 by a “reinterpretation” allowing the SDF to defend allies upon whom war has been declared.

Japan’s self-defence policy is supplemented by a parliamentary resolution (never made into law) that has guided nuclear policy since the late 1980s. Said to reflect majority public opinion, the resolution, reaffirmed by incoming prime ministers, states that Japan shall neither possess nor manufacture nuclear weapons, nor shall it permit their introduction into Japanese territory.

Despite Japan’s non-nuclear status, the SDF’s growing size and efficiency began attracting regional attention in the early 1970s. In an effort to calm foreign fears, the Gaimusho (Foreign Affairs Ministry) invited foreign correspondents to spend a month touring SDF facilities and interviewing policy-makers. The ministry offered to pay all expenses. The publication for which I then wrote declined the subsidy at my suggestion but let me take advantage of the door-opening offer. I spent a full month inside the SDF throughout Japan.

The access I was granted was impressive. I spent time with Lockheed F-104 Starfighter pilots on alert at Chitose Air Base in Hokkaido waiting for Soviet Bear bombers that were given to intruding on Japanese airspace as they flew from Siberia to North Vietnam. I interviewed the stern but humorous captain of an SDF destroyer who was the force’s last senior officer to have served in the Japanese Imperial Navy. When I referred to his command of a “warship”, he corrected me: “There is no ‘warship’ here. Japan no longer makes ‘war’, Paul-san.” His destroyer’s duty was self-defence.

In Iwakuni, I had afternoon tea with Nobuo Fujita, a maker of trout-fishing flies who had flown a small reconnaissance floatplane over Sydney ahead of his submarine’s shelling of the city in 1942. At the naval history museum at nearby Etajima, I was shown a vial containing tears shed at the funeral of Marshal-Admiral Marquis Heihachiro Togo, hero of the Battle of Tsushima Straits, where the Japanese trounced Russia’s fleet in 1905.

One of my guides was a chief petty officer who had been slated for combat in a kamikaze suicide squadron at noon on August 15, 1945, the day the Second World War ended. His sortie against US warships was cancelled. He felt obliged to compensate for his good fortune by doing everything at the double. I saw no need to try to keep up.

It was an unusual, even uneasy time. The US imbroglio in Indochina was worsening, with the Americans looking less convincing as a defender of allies’ interests in Asia. Article 9 was a discussion point throughout Japan. To what extent did the clause prevent Japan from acquiring weapons that could be described as self-defence? For example, could Japan, within its stretched definition of self-defence, create nuclear mines and sow them around her borders to deter any invasion force? (One wry wit at the Foreign Correspondents’ Club in Tokyo invited us to speculate about the SDF’s legitimately acquiring nuclear hand grenades!)

Right-wing nationalist politician Yasuhiro Nakasone would soon become prime minister (1982 to 1987). As head of self-defence in 1970, he had advocated Japan’s acquisition of tactical nuclear weapons. Disliked for his arrogant manner and what was thought to be anti-Westerner attitudes, he was known among irreverent younger staff at the Australian Embassy as Knackers-One or, if his fondness for imperial Japan was in discussion, sometimes Knackers the First.

There were unconfirmed reports that North Korea was sending troops and aircrew to Vietnam. (In 2001 an official Vietnamese war history confirmed that “in 1967 a number of pilots from the Korean People’s Liberation Army were sent to Vietnam to … participate in combat operations … On a number of occasions Korean pilots scored victories by shooting down American aircraft.”) Such stories fuelled fears that if Indochina’s wars ended unfavourably for the US, Great Leader Kim Il-sung would restart the Korean War, finally forcing his way past the perimeter that MacArthur’s forces had been able to hold around Pusan in 1950 and forcibly reuniting the Koreas under a communist Pyongyang.

Kim visited Chairman Mao Zedong in Beijing about two weeks before Saigon’s fall to North Vietnamese forces. In a book published in 2016, The Last Heavenly Dynasty: China and North Korea in the Age of Mao Zedong and Kim Il-sung, East China Normal University history professor Shen Zihua says that Kim’s purpose was to obtain Mao’s support for a renewed war that would reunify the two Koreas. But Mao, says Shen, quoting official documents, avoided discussing the matter. By then, Mao was more interested in further improving relations with the US, a process launched by President Richard Nixon’s visit to Beijing three years earlier.

In SDF officers’ messes and at the National Defense Academy in Tokyo one heard discussions of the implications of a “Red Flag at Pusan”. A wholly communist Korean Peninsula would then point like a dagger at Japan’s midriff. Some analysts urged that Japan adopt what was described as an “N-Day minus” policy. N (for nuclear) day would be the date on which Japan would have the bomb. After the word minus would be placed the number indicating months to acquisition. N-Day minus twelve was said to be on the outer limits of what was thought possible.

Many old Asia hands have long been convinced that Japan has had a secret N-day project in the works, that all Japan’s nuclear weapons need are a screwdriver and political will. Reference is often made to the Japanese having a “bomb in the basement”.

Such a step would be extremely difficult to achieve secretly. The from-the-bottom-up Japanese decision-making practice known as nemawashi (literally: digging around the roots of a tree to prepare it for transplanting) involves widespread consultation. As a consequence, Japan’s politicians and bureaucrats do not have a high reputation for keeping secrets.

No convincing revelations of a nuclear basement have ever surfaced but the rumours persist. From time to time restless neighbours like China point to Japan’s huge stockpile of plutonium, a by-product of reactors used to generate Japan’s commercial energy; Japan owns nearly fifty tonnes of separated plutonium. That is enough for more than 5000 nuclear weapons. Japan has no feasible peaceful use for most of this material.

Given Japan’s defence-spending levels, it would not be unreasonable to assume that Japan will be our region’s next nuclear power. But just how likely is such a development?

There are two sharply differing views—call them the nuclearists and the sceptics. One camp says that a nuclear Japan is highly likely, even inevitable. The other suggests that such an idea does not survive scrutiny.

The nuclearists

The Japanese are no strangers to nuclear physics, the nuclearists point out. In 1943, for example, the Nishina laboratory in Kanda completed construction of several cyclotrons (circular particle accelerators used in the study of nuclear transformations). On the morning of November 22, 1945, without advance warning, US troops rolled up in trucks and began dismantling these machines, some GIs using axes and dynamite. The remains were dumped into Tokyo Bay. But subsequently Japan, notoriously short of energy resources, developed a substantial nuclear-power program.

Plutonium extracted from spent nuclear fuel is usually weapons-grade Pu-239 mixed with Pu-240 and other elements. Isolating the pure Pu-239 needed for a bomb is a relatively easy step. Needless to say, the precision machining then needed to construct a warhead from this metal is well within Japan’s capabilities.

Warhead designs are best developed in laboratories equipped with very large glass lasers that simulate nuclear explosions by training energy on pellets of fissionable material. Osaka University’s Institute of Laser Engineering has had since 1983 at least one such machine—the Gekko XII laser built for civilian laser fusion power applications.

So, given all these capabilities, how far away from nuclear-weapons status is Japan? With a crash program, Japan could have a warhead and thus be a nuclear power in a year or less. It would need only to add the political will to its current capability.

In some circles this will clearly exists. In 1999, the Defense Agency’s vice-minister Shingo Nishimura told the Washington Post:

As long as two sides have nuclear weapons, there is no chance of nuclear war. The risk is much greater when a country does not have nuclear weapons. Japan is therefore in a most dangerous situation. The Diet really should look into finding a way to arm Japan with nuclear weapons.

The sceptics

For more than twenty years an old acquaintance, the late Makoto Momoi, formerly a professor at the Japan National Defense Academy, disputed the value of nuclear weapons to Japan. Recent weapons developments had made him even more of a sceptic: “Because Japan’s population is so densely concentrated,” the professor told me before his death in 2004:

only a submarine-based nuclear force somewhere in the Pacific would have any second-strike credibility. But if Japan had a nuclear weapon, who would be the target? Countries of the former Soviet Union? Unlikely. Their most important population and industrial concentrations are west of the Urals, a long way from a Japanese submarine in the Pacific. China is closer, but China’s population is highly dispersed.

There is, though, one nation with 25 per cent of its population in its ten biggest cities and they’re all reachable from the Pacific. That nation is the United States.

So, Russia too far; China too big; only America is plausible—and, of course, unthinkable. Therefore, to those who talk about a Japanese nuclear weapon I say the notion is ridiculous!

The five major nuclear powers [the US, Britain, France, Russia and China] can test with relative ease: They have either access to deserts or the arrogance to test in the Pacific. Japan has neither deserts nor such arrogance.

Moreover, for second-strike credibility you need highly advanced radar and intelligence gathering and a people willing to accept the damage of a first strike. Japan has none of these.

We’re even vulnerable to a North Korea using rockets with conventional warheads. Pyongyang could fire a rocket at Japan to show they can hit us. Then they could say, “The next one is aimed at one of your nuclear plants.” What could we do?

Most importantly, nukes in general, in my view, have gradually become a less effective weapon for hitting targets. The reason—development of highly precise guidance mechanisms for warheads that will give us and other technically advanced nations the advantage of hitting a minute target in a bull’s-eye fashion. Hence there is no need for nukes that devastate a large area in order to destroy a small target.

Professor Momoi was referring to an imminent generation of space-based weapons sometimes referred to as the “Rods from God”.

Science-fiction writer and space-weapons expert Jerry Pournelle first came up with the concept while working for Boeing in the late 1950s. No nuclear energy or for that matter any explosives at all need be involved. Instead, slender solid tungsten cylinders twenty or thirty feet long and one or two feet in diameter would be sent into space and aimed from satellites.

The rods, which the US Air Force lists as “future system concepts”, would hit a target—a North Korean rocket or artillery bunker, for example—at speeds of more than 10,000 feet per second, penetrating deeply into the earth and creating devastating non-nuclear destruction. Pournelle named his concept Thor, after the ill-tempered, hammer-wielding god of Norse mythology. Others have likened the rods to a “weaponised meteor strike”.

Thus, the debate continues, without any apparent decision—nothing revealed to the public, anyway. The delay might well have surprised the late Professor Mimura. But perhaps he would also be reassured by the knowledge that if the Japanese should ever feel the need, they could have nuclear weapons within months.