--Is it needed and even if so how can it be achieved?--
Akio Kawato

North Korean missiles are becoming a real threat for Japan (more correctly for the American bases in Japan). Though there is no panic in the Japanese society and voices for amending the pacifist Constitution have not grown, discussion is quietly rising about nuclear armament of Japan. Some pundits in the US have also started a similar debate, perhaps with an intention to part from defense of Japan. Does Japan need its own nuclear arms, and even if so will the pacifist Japanese society and the outside world, still wary of Japan's military might, allow it? And if a "permission" be given, what kind of deterrence would be most feasible?

Up to now the US "nuclear umbrella" has been sufficient

After the defeat in the Second World War Japan, like Germany, was deprived of capability to become a military power again. Nuclear armament was a particular taboo for Japan, and this was legally fixed in the Treaty on the Non-Proliferation of Nuclear Weapons; Japan reluctantly signed it in 1970. Since then, though Japan kept technology for producing nuclear weapons, Japan relied upon the "nuclear umbrella" offered by the US.
This arrangement has been valid vis-à-vis the nuclear missiles of the Soviet Union later Russia and China. And the new-comer, North Korean long range nuclear missiles, does not bring any substantial change in the picture. Lately we hear an argument "Once North Korea can send its nuclear missile to the US, the latter will distance itself from defense of its allies in East Asia", but this is a wrong judgment; if the US has been able to deter Russia and China, why not North Korea,too.

(There is, however, one caveat. During Obama administration the nuclear warheads which used to be mounted on sea-launched Tomahawk cruise missiles were totally removed and scrapped. So today the nuclear deterrence, which the USA can offer in the Pacific, is limited to intercontinental nuclear missiles stationed in the US, long-range nuclear missiles carried by nuclear submarines, and nuclear bombs and nuclear-headed long-range cruise missiles on long-range bombers stationed in Guam.
This composition is not firm enough, because the long-range missiles are intended against big powers like Russia and China, and they should not be easily used against smaller countries like North Korea. The long range bombers are easy targets for enemy's preventive attacks. Therefore, the lack of one "ladder", that is submarine-based cruise missiles with nuclear warheads, is greatly missed.)

The chain reaction--peace treaty for the Korean War⇒withdrawal of the American troops from South Korea⇒unification of Korea－will change the paradigm

This time in spite of all vilification to each other the US will not make an armed attack on North Korea; it may lead to preventive or retaliatory attacks by North Korea on the American bases in South Korea and Japan (the United Nations Command Rear for the Korean Peninsula is situated in Yokota air base, suburb of Tokyo) and a protracted war, inflicting unbearable damage to South Korea, too.

North Korea, either, does not want any war with the US. What it strives for is a true recognition of their sovereignty with a guarantee for non-interference (no "regime change"), recognition of their status as nuclear power and, if possible, signing of an ultimate peace treaty on the Korean War.

If the current turmoil be settled with a reconfirmation of the armistice on the Korean War and an agreement to "freeze" the North Korean nuclear weapons at today's level, things will not change substantially. Japan will be content with the nuclear umbrella of the United States.

However, if a peace treaty on the Korean War be signed, a chain reaction will occur and the situation in East Asia will have a substantial alteration. Namely, if a peace treaty be concluded, the US will largely lose justification to keep its troops in South Korea. In the latter the latent anti-US emotion will come to surface, urging the US to withdraw its forces. Meanwhile, voices for reunification of Korea will mount both in South Korea and North Korea (with different calculations).

Unified Korea will be a large power with its GDP slightly larger than that of Russia and with nuclear armament. The Koreans are possessed with anti-Japanese, anti-American and anti-Chinese sentiments, and these emotions come to front in turn; the country's foreign policy will keep vacillating.

What would this mean for Japan? Even if the US withdraws its troops from South Korea, it will not automatically lead to evacuation from Japan. If a strong, nuclear and anti-Japanese unified Korea pops up next door, the Japanese will covet maintenance of Japan-US security alliance.
And for the US, too, the military bases in Japan and the political and economic collaboration with Japan--its political role is positively valued by ASEAN countries and Taiwan, and it still possesses the third largest economy in the world--, are sine qua non for maintaining the US' leading role in Asia.

For the US the trade with Asia is no less important as the trade with Europe, but without alliance with Japan the US will eventually have to abide by the rules which China imposes, thus making all deals less advantageous. What is more, the Japanese government annually pays more than 5 billion dollars for upkeep of the American forces in Japan.
Will the unified Korea resort to a "nuclear blackmailing" vis-à-vis Japan to realize its political and economic demands? If that happens, Japan will need to possess its own nuclear umbrella, because the US may take a neutral position
toward Japan-Korean political conflict, urging Japan to become more generous.
However, reason tells me that the unified Korea most probably will not resort to a nuclear bluff to Japan, because the unified Korea will have to engage in delicate balance act between China, the United States, Russia and Japan and therefore it will not opt for alienating Japan too much.

True that international politics does not always move as reason orders. The unified Korean government may lose control of anti-Japanese outburst, Chinese leader may take a bellicose attitude toward Japan only to consolidate his or her power and, finally, the US may become so introvert that it on a whim leave its military bases in Japan, which had cost hundreds of thousands US soldiers' blood during the Second World War. So, in this case a nuclear option for Japan, nevertheless, would become necessary.

A viable deterrence for Japan

Any sovereign state would want to have its own deterrence against foreign attack. Even the pacifist Japanese Constitution, according to the official interpretation, does not prohibit Japan to possess self-defense capability; that is why Japan has highly-developed armed forces in the name of the Self-Defense Forces. In the same token the Constitution does not hinder Japan from acquiring deterrence devices against nuclear attack, be it non-nuclear (e.g. missile defense) or be it nuclear.

It is true that Japan upholds "three nuclear free principles: to accept, to produce and to purchase no nuclear weapons", but this is a resolution of the Parliament and can be changed more flexibly than the Constitution.

However, in international politics Japan's hands are tied. Currently Japan is a member of NPT (Treaty on the Non-Proliferation of Nuclear Weapons). The "Agreement for Cooperation Between the Government of the United States of America and the Government of Japan Concerning Peaceful Uses of Nuclear Energy" prohibits Japan to use uranium for production of nuclear arms. And the majority of the Japanese has a strong nuclear "allergy"; Japan is the only country in the world on which nuclear bombs were tested on human-being.

As long as Japan stays within these limits Japan can only exhort the US to equip the submarine-based Tomahawks with nuclear warheads again and to cordially "share" some of them with Japan. This will be a maritime version of US-German "dual key" formula, in which German government can propose the US to detonate tactical nuclear devices against invading adversary forces.

But if the situation around Japan becomes even more precarious, Japan may opt for independent nuclear armament. In that case Japan needs consent of the US so that the latter will not stop supply of uranium to Japan. The US may well give a go-ahead signal just like in the cases of India and possibly Israel; both countries remain close allies of the US (but they are not members of the Treaty on the Non-Proliferation).

In this case Japan will prefer to keep its nuclear devices in the sea because it would not incur adversary's preventive attack to the land of Japan. Purchase of submarines with nuclear-headed missiles (either from the US, Great Britain or France) will be the quickest solution.

All this does not and should not mean that Japan again becomes an aggressive military power. Japan is busy coping with the global economic competition, and dealing with the challenge which the "Fourth Industrial Revolution" poses. And Japan simply lacks in money to pay for militarization, because it needs even more resources for its ageing population.

Nation-to-nation confrontation is a phenomenon which belongs to the 19th century, and I hope that the countries in Asia will eventually get the better of excessive nationalism.
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