A sense of alarm is rising throughout the world as North Korea follows up its war rhetoric with two intercontinental ballistic missile tests, a missile launch plan aimed at Guam, a missile launch over Japan, followed by its sixth nuclear — and possibly its first successful thermonuclear — bomb test. North Korea is on the verge of establishing the ability to mount a miniaturized thermonuclear warhead on an ICBM that could reach Washington, London or almost anywhere else.

North Korean leader Kim Jong Un and his regime are making every effort to acquire nuclear deterrence vis-a-vis the United States without fear of failure and isolation. Kim may seem desperate and losing his senses. But make no mistake; he is not mad despite his unique appearance and belligerent rhetoric. On the contrary, his actions are rational when viewed from the perspective of nuclear deterrence theory.

It makes strategic sense for North Korea to develop multiple strike capabilities while enhancing their survivability with solid-fuel technology, road mobility and submarine-launch technology. North Korea must still successfully develop warhead re-entry technology and will also seek MIRV technology — placing multiple independent warheads on each ballistic missile — to make them more difficult for the U.S. to intercept. But it's a matter of when, not if.