[CaptainCrunch]

Just given the current situation it might pay to understand how a ballistic missile defense would work for Japan.

Currently there are two levels, sea born and land born.

Sea born uses the SM-3 Block three air defense missile, these are mounted on Aegis equip destroyers that both the Japanese and the Americans have in the sea of Japan.

Japan also has the land based Patriot PAC-3 Interceptors, the Americans at Guam have the Thaad system.

The Korean IRBM has three phases, the launch phase, midcourse and terminal phases.

For missile defenses probably the best place to intercept would be the launch phase, that way your destroying the missile and payload as it launches over the enemy territory.

From my understanding while such systems are in development they're not available.

The SM-3 is designed to destroy a IRBM in midcourse, however the difficulty here is that they would be deployed to destroy a midcourse track that would impact in Japan, since this launch was over Japan it was effectively from my understanding out of the range and capability of the SM-2.

The PAC is designed to hit a missile entering its terminal phase, its also designed to destroy the debris of a destroyed missile, However while the THAAD is specifically designed to destroy a extremely fast IRBM in its terminal phase, the PAC-3 is designed to destroy slower moving non IRBM's in their terminal phase, in other words the PAC-3 missile isn't fast enough to intercept the type of missile that Japan was firing.

Again plus once they saw the missile was going over Japan, it likely meant that the missile was still in midcourse anyways.

If North Korea launched a IRBM at Japan, they realistically have one of the three layers of defense, they can deal with it midcourse. If it was a slower missile they would have two layers of defense.

Since this missile was flying over Japan, they didn't have the capability in theatre to shoot it down.

However I'm pretty sure that launch phase defenses just got a whole ton of funding.