Although the findings that my colleagues and I reach (see “North Korea’s 'not quite' ICBM can’t hit the lower 48 states”) indicate that the United States is still many years away from potentially being under threat from North Korean nuclear-armed ballistic missiles, North Korea clearly has substantial resources for advancing its ballistic missile programs and is definitely learning how to adapt and control the Russian liquid propellant rocket motors it obtained roughly 30 years ago. This suggests that an ill-considered or complacent approach to the development of intercontinental range rocket systems by North Korea is not likely to be a sound future strategy for the United States and its allies in Northeast Asia.
One of the obvious and most important ways to try to achieve a long-range solution to a potential future threat to the continental United States from North Korea is diplomacy—which is now actively being discussed at the highest levels of the US government and the other governments directly affected, including China, South Korea, Japan, and Russia. All these states, and North Korea, have big interests in an equitable and viable long-term political solution for the situation on the Korean peninsula.
There is a potentially useful way to provide military support for these diplomatic efforts: a US commitment to rapidly develop a specialized kind of ballistic missile defense that could shoot down a North Korean ICBM immediately after it is launched and while it is still in powered flight.
Once a ballistic missile has completed its powered flight and is in the near vacuum of space, current US missile defenses become extremely vulnerable to the simplest countermeasures. These missile defenses have essentially no reliable, science-based way of telling the difference between warheads and very simple decoys. There are also numerous other countermeasures that could be used by an adversary like North Korea to defeat the homing capabilities of US high-altitude interceptors.
In sharp contrast to current US missile defense concepts, defenses that could destroy North Korean ICBMs immediately after launch and before they have completed their powered flight are well within the technical capabilities of the United States. If developed rapidly, these boost-phase missile defense systems could provide an effective counter to North Korean missile development efforts and serve as an incentive for the North Koreans to negotiate a reasonable agreement that stabilizes the standoff over Pyongyang’s nuclear program.