The Japanese government has decided to purchase and deploy a 2-layered ballistic missile defence system by 2007. Forward defence will be provided by the latest version of the SM-3 "Standard" missile, which will operate from Kongo-class navy destroyers eqipped with AEGIS radars. Backup defense will come from PAC-3 "Patriot" missiles. Parapundit analyzes the implications in detail, with lots of links as usual.
Obviously, North Korean behaviour is a big factor. I'm kind of disappointed the Japanese didn't go for an early deployment of the Israeli Arrow2 missile system, which has 2 batteries in operation now and could provide a wider-coverage defense option much sooner than 2007... I don't think Japan will be given that much time before something is needed, even if only for deterrent value.
At the risk of getting repetitive: The United States needs to develop weapons that can take out artillery dug into mountainsides. Maybe FAEs? Maybe artillery shells that have radar that can guide them to where the shells are coming from? Maybe small robots to drop down by parachute that can crawl around and find holes in the ground that have artillery coming out of them?
The US also needs to pull its troops back from the DMZ more rapidly. It also needs to build up air power projection capabilities in the Pacific.
Can Israel make Arrow2 systems faster than Raytheon can make PAC3 systems? Relative costs and capabilities?
But most of all: We need to break the North Korean regime's information monopoly over its own people.
[1] PAC-3s are point defense, not theater defense. Japan needs theater defenses to start.
[2] Artllery dug into mountains can survive even nukes. There may not be a solution that lets us remove the threat. Copperhead shells are guided, but you have to know where before the enemy artillery fires. Research into point defense against artillery is ongoing, but no v1 system would not be able to handle the volume the NKs could throw at it.
The traditional solution, used by Israel for the Golan Heights, is to have the enemy's Asst. Defense Minister as your spy and learn where all the emplacements are. This may or may not e realistic.
[3] Agree with the DMZ pullback. You know South Korea will work to make that as difficult as possible. Airpower projection is being enhanced at Okinawa, at least.
[4] The information monopoly should be done because it's safe and it accomplishes something. I believe we could be completely successful and it still wouldn't lead anywhere in terms of regime change. This is not a 1990s communist regime gone soft, and as long as they are willing to commit mass murder to stay in power information alone means little.
I agree that information control is vital, but how do you propose breaking that control that Pyongyang has?