The Yomiuri Shimbun The U.S. government’s confirmation that the missile North Korea fired Tuesday was an intercontinental ballistic missile has suddenly made the prospect of a North Korean ICBM flying through the sky over Japan and toward the United States a more realistic possibility. Although security-related legislation that came into force in March 2016 made it legally possible for Japan to intercept such a missile, such an operation can only be conducted under strict conditions, and high technological barriers also remain.
The legislation incorporates three new conditions on the use of force set forth by a Cabinet decision in July 2014 to reflect a change in the interpretation of the Constitution. These conditions are: an armed attack occurs and threatens Japan’s survival; there are no other appropriate means to protect Japan’s people; and use of force is restricted to the minimum necessary. Only if these three conditions are met would Japan be able to use force and shoot down a ballistic missile heading toward the United States.
If North Korea launched a ballistic missile aimed at Hawaii, home of the headquarters of the U.S. Pacific Command, or at Guam, which the United States would use as a base for launching operations to respond to a contingency on the Korean Peninsula, it would fly over Japan. The government is unsure whether Japan could legally intercept this missile in such a scenario.
“It is difficult to answer, in general,” Defense Ministry spokesman Hirofumi Takeda said.
However, if war broke out between North Korea on one side and the United States and South Korea on the other, and the government deemed that Japan’s survival was in danger under the three conditions, such a missile could be intercepted as a self-defensive measure.
By contrast, Japan could not legally shoot down a North Korean ICBM suddenly launched toward the United States in peacetime.
Technological and capability problems also remain. Japan’s current missile defense system centers around Aegis destroyers equipped with SM-3 interceptor missiles that can shoot down a target outside the atmosphere up to a maximum altitude of about 500 kilometers. SM-3s are expected to shoot down a ballistic missile, which flies through the air in a parabolic trajectory, just as it begins to fall from its highest point. But an ICBM fired at the United States would have increasing altitude at a high speed when it passes through the sky over the Aegis vessels stationed in the Sea of Japan.
“It would be very difficult to intercept such a missile in the first place,” a senior Defense Ministry official said.
The possibility of shooting down an ICBM likely would be increased if Aegis vessels were stationed in the Pacific Ocean and equipped with the SM-3 Block IIA interceptor missiles being developed by Japan and the United States. These missiles will be able to shoot down a target at an altitude of more than 1,000 kilometers.Speech