North Korea’s sixth nuclear test raised the threat level posed by the country, making the possibility of nuclear missile more realistic. The Defense Ministry is expediting the enhancement of its missile defense capability by allocating funds for Aegis Ashore, a ground-based missile-interception system, and for improving the existing missile defense system in the FY2018 budgetary request. However, it has become clear that the DPRK’s technological advancement has rendered Japan’s deterrence insufficient against missile launches on lofted trajectories and saturation attacks even with enhanced missile defense capabilities,
“Ballistic missile defense is aimed at intercepting missiles before their reentry into the atmosphere,” Defense Minister Itsunori Onodera told the press on Sept. 9. “We also need to be capable of countering North Korea’s electromagnetic pulse (EMP) attacks.” The defense minister emphasized that he will take thorough measures to respond to EMP attacks using missile defense. EMP is a means of attack in which gamma rays generated by nuclear detonation paralyze electrical systems, thereby wiping out urban functions and the missile defense shield. After carrying out a nuclear test on Sept. 3, North Korea claimed that it is now capable of conducting an EMP attack.
SM-3 Block 2A, a new type of interceptor missile being developed by both the U.S. and Japan, is capable of intercepting a target at an altitude beyond 1,000 km. This could be effective against an EMP attacks as it causes nuclear explosions at several tens to hundreds of kilometers above ground. The missile is expected to be used for the Aegis Ashore system.
If the SM-3 fails to intercept a target, the Defense Ministry has a backup plan to intercept the target using a Patriot Advanced Capabililty-3 (PAC-3) interceptor missile. However, EMP is not the only problem for Japan. On July 28, North Korea launched a Hwasong-14 intercontinental ballistic missile (ICBM) on a lofted trajectory and the missile reached an altitude of about 3,700 km. Neither the existing SM-3 interceptor, for which the maximum altitude is 500 km, nor the SM-3 Block 2A, which is still under development, would be able to shoot it down.
The DPRK also has 800 Scud ballistic missiles that are capable of reaching Japan, and 200 Rodong ballistic missiles that can target any part of Japan. This means North Korea can stage a “saturation attack” by firing multple missiles toward Japan to overwhelm the country’s interception capability. The Defense Ministry plans to increase the number of Aegis destroyers from the current four to eight. Each destroyer is armed with eight SM-3 missiles. Thirty-four PAC-3 missiles are deployed across the country primarily to defend large cities. If the DPRK carries out a saturation attack, there is no guarantee that all incoming missiles can be shot down.
The fundamental issue is that missile defense is insufficient as a deterrent against North Korean missile attacks. There are two types of deterrence: “deterrence by denial” to cause an enemy’s attack to fail and “deterrence by punishment” to make the enemy give up on attacking by demonstrating the capability to cause intolerable damage to the enemy. Missile defense only constitutes deterrence by denial.
The possibility cannot be ruled out that the Trump administration will make a deal with North Korea in which it forces the DPRK to get rid of its ICBMs, which are capable of reaching the U.S. mainland, in exchange for allowing it to keep its medium-range ballistic missiles. Unless Japan has its own attack capability, it would be difficult to prevent the U.S. and North Korea from making such deal. If Japan has its own attack capability, it might also serve as a deterrent against China as the country opposes Japan’s military buildup. China might harden its stance toward North Korea as a result, but there are no clear signs of that happening at the moment.