Why have some of Japan’s leaders been talking about the need to acquire the ability to attack North Korean missiles on the launchpads? It’s because they know that the United States, despite its overwhelming air and maritime power, cannot credibly threaten North Korea. That is because North Korea holds Seoul hostage by threat of artillery and rockets. Thus Pyongyang’s dangerous nuclear and missile brinkmanship is potentially destabilizing.

Moreover, North Korea has given Japan a strong case for developing nuclear weapons with which to deter China, without Japan’s having to say so. So East Asia could be on the brink of a spiral toward dangerous nuclear confrontations over which the U.S. would have little influence.

Currently, Japan has no ability to target North Korean missile launch sites. Thus talk from Chief Cabinet Secretary Shinzo Abe about future preemptive strike options is partly domestic politics. Abe, by representing himself as tough on North Korea, wants to cement his claim as successor to the prime minister’s post when Junichiro Koizumi steps down in September. But more than domestic politics is involved.

If Japan were serious about acquiring the ability to hit a North Korean missile on its launchpad, the weapon of choice would probably be a highly accurate “land attack” cruise missile of the Tomahawk variety. These missiles can be launched from surface ships, aircraft and submerged submarines. The Tomahawk was developed in the 1980s to give the U.S. president some conventional options so that in a crisis with Moscow he would not have to choose between nuclear Armageddon or capitulation.

But if Japan were to start thinking about acquiring such a land attack cruise missile, it would be doing so in a very different strategic context — not an environment in which two nuclear-armed superpowers had reached strategic parity and knew that a collision between them would be simply too dangerous, but one posing a much more multidimensional threat.

Many questions arise from Japan’s talking openly about acquiring preemptive strike capabilities. Would Japan need to attack North Korean missiles with nuclear warheads, or would nonnuclear weapons be sufficient? If Japan could be confident of taking out North Korean missiles with conventional warheads, this could add to the case that Japan still has no need for nuclear weapons.

And what about China? China is North Korea’s quasi-ally, and targets Japan with nuclear weapons. Japan might think that it could deter China with conventionally armed cruise missiles. But China is so big that it would be a sponge for such missiles.

So if Japan starts to think it needs offensive conventional weapons, it could be a slippery slope toward acquiring nuclear weapons. And Japan, by acquiring nuclear weapons pointed at North Korea, would then be able to deter China without needing to say so. True, missile defense meets Japan’s strategic needs because it is nonnuclear and defensive. But there is no guarantee that it is going to work. And as presently configured, missile defense will not work against the sophisticated cruise missiles that China has been developing with Russian help.

In 2003, then Japan Defense Agency chief Shigeru Ishiba talked publicly about the need for preemptive strike options. He also hinted that Japan might ask Washington to sell it the Tomahawk, which Britain has been allowed to purchase. That issue went on the back burner because of opposition in Japan’s ruling coalition. But it will be back on the front burner now that North Korea has again behaved provocatively.

So if Japan now formally asks the U.S. to sell it Tomahawk land-attack cruise missiles, what would that mean? Many observers would conclude that in vastly changed strategic circumstances, Japan is no longer willing to rely for its nuclear security on the U.S. umbrella and the prospect of missile defense.

Moreover, the alternative to extended deterrence is not conventional capability, as many people seem to think. To the contrary, the end of extended deterrence would very likely usher in nuclear proliferation in East Asia.

If America were to refuse to sell the Tomahawk to Japan, Japan could develop it anyway, possibly in cooperation with its friends in Taiwan. And an American refusal would make it obvious that there was not much trust in the U.S.-Japan alliance. That should not surprise us greatly. Nuclear weapons and the means of their delivery have a habit of disclosing the bedrock interests of states in a self-help and dangerous world.

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