Japan Institute for National Fundamentals

　　　　　North Korea has recently conducted its fourth nuclear explosion test, posing grave threats to Japan’s national security. The largest deterrence against nuclear weapons is nuclear arsenal. Japan has the deterrence by forming a military alliance with the United States, the largest nuclear-armed country in the world, to be put under the U.S. nuclear umbrella. At top-level Japan-U.S. talks over the phone just after the North Korean nuclear test, U.S. President Barack Obama reportedly reaffirmed that the United States would take every means to defend Japan.
　　　　　But Arthur Waldron, professor at the University of Pennsylvania, told a symposium sponsored by the Japan Institute for National Fundamentals in December 2014 that he could not believe in the nuclear umbrella guarantee. He gave the following warning:
　　　　　“Washington has publicly offered to defend Japan if it comes under armed attack. As an American, I would not believe in the offer. Will America really use nuclear weapons to defend an ally? The answer is No.”
　　　　　Prof. Waldron then proposed that Japan own the minimum nuclear deterrence: a nuclear-powered submarine with nuclear missiles put in operation to retaliate against any nuclear attack on Japan.

Latest test designed to miniaturize nuclear weapons
　　　　　North Korea’s nuclear weapon development started at the initiative of its then supreme leader Kim Il Sung just after the 1950-53 Korean War and gained momentum in or after the 1960s, accounting for the core of its military strategy. It is wrong for many experts to explain that North Korea has gone nuclear to maintain its political regime after the end of the Cold War.
　　　　　North Korea has concluded that it failed to win in the Korean War due to the presence of U.S. military bases in Japan. In any next war, the North attempts to make U.S. bases in Japan dysfunctional by attacking them with nuclear or other weapons and prevent U.S. forces in Japan from participating in the war by threatening Japanese and U.S. governments and peoples with nuclear missiles.
　　　　　When you look at the latest test from this perspective, you can find its central aim was to miniaturize nuclear bombs for their mounting on missiles, rather than developing a hydrogen bomb. North Korea’s final goal is to operationally deploy nuclear missiles that can reach the U.S. mainland. Given the final goal, we can imagine that North Korea had a technical problem that it should solve by conducting a test even at the cost of leading its relations with China to deteriorate. Therefore, North Korea could have tested an enhanced bomb using deuterium or tritium to miniaturize a bomb.

Japan put within nuclear attack range
　　　　　In February 2015, Joel Wit, senior fellow at Johns Hopkins University, said plutonium-type nuclear weapons had been miniaturized enough to be mounted on the Rodong medium-range and Taepodong-2 long-range ballistic missiles. As the Rodong missiles have already been deployed, we should think that Japan is now within North Korean nuclear attack range.
　　　　　A threat is a combination of capabilities and intentions. North Korea might have the capability of launching nuclear attacks on Japan. Its leader Kim Jong Un is impulsive and offensive and has an intention to launch nuclear attacks on Japan. Japan must seriously consider how to have deterrence against North Korean threat. The time has come for Japan to seriously study the Waldron proposal.

Tsutomu Nishioka is Planning Committee Member, Japan Institute for National Fundamentals, and Professor at Tokyo Christian University.