I had the chance to discuss the North Korean bomb test with a senior scholar who studies “bombs” for a living. He reports the following as the current consensus among international-security types:
1. The test was almost certainly a fizzle.
2. The North Koreans were probably trying to test a deliverable warhead (i.e., something small enough to be a warhead on the cruise missiles they have) rather than a mere test device. That increased the risk of a fizzle.
3. The intended yield was about 4 kilotons. That’s about a quarter the size of the Hiroshima bomb. Since the area of destruction grows as the square root of the yield, that means it would destroy about half the area that the Hiroshima bomb took out.
4. The obvious target for such a warhead would be an aircraft carrier. If North Korea were known to have nuclear-tipped cruise missiles, our carriers — which in the past have been used to threaten North Korea — would have to keep their distance.
5. Unlike a nuclear attack on a city (by North Korea or by a terrorist group to which North Korea had supplied a nuclear weapon), which would be national suicide, an attack on a purely military target such as a carrier would look more like an ordinary act of war than it would like an act of mass murder, especially since an attack over water minimizes radioactive fallout. The North Korean government could then reasonably hope to escape massive retaliation.
6. The tactical purpose of the test was to force the U.S. back to the bargaining table. The strategic objective is a security treaty under which the U.S. promises not to invade.
7. From that perspective, the test was probably a mistake; net-net, the North Korean bargaining position just got worse rather than better.