In the lead-up to the launch of the Unha-3, Pyongyang moved the launch window and made it appear to satellites that it was removing its rocket from the launch pad. Just before carrying out the nuclear test, Pyongyang toned down its public test warnings (though it apparently sent last-minute warnings to Washington and Beijing). The pattern is part of Pyongyang's efforts to keep potential observers guessing. However, while some Western media took North Korea's latest statement at face value, the South Korean government and media continued to caution that Pyongyang was likely to test this week.
It is not clear yet what sort of device North Korea tested. Initial estimates suggest a 6- to 7-kiloton yield, which is slightly larger than past North Korean tests. Prior to the test, it was suspected that the North would test a uranium device as a follow-on to its two earlier plutonium tests. This would mark another step in North Korea's nuclear program, though North Korea has long been known to be working on a secondary uranium program, and in some ways a nuclear reaction with uranium is technically easier to effectively detonate than a plutonium reaction. It also could be a third plutonium test, as North Korea continues to refine its nuclear program and work toward a viable nuclear weapon, as opposed to just a nuclear device. Follow-up analysis of the seismic signature and air samples taken over the site will offer additional information in coming weeks.
Although Pyongyang has pursued a strategy of survival based on presenting a fearsome, irrational yet weak image, the North views its nuclear and missile program as more than just a bargaining chip. Pyongyang is pursuing what it considers a viable deterrent: a weaponized nuclear device that can fit on a missile. This would not be to keep its neighbors at bay — they are already within reach of North Korea's conventional weapons — but to offer the North a deterrent in relation to Washington (though a small number of nuclear missiles would not significantly threaten the United States). Pyongyang also sees in the program a way of removing its dependence on China. Pyongyang has sought an independent deterrent in order to feel confident enough to either open direct talks with the United States to end the state of armistice in place since 1953, or to simply move forward with some elements of domestic economic experiments, more confident that it can dissuade U.S. interference.
By keeping the program seemingly viable but ambiguous (underground tests, space launches, but no proof of weaponized nuclear warheads and effective long-range ballistic missile guidance systems), Pyongyang is seeking deterrence while trying not to trigger military pre-emption. Although there will be a loud outcry from the international community and additional sanctions on North Korea, nuclear testing and rocket launches are becoming routine for the North, which is perhaps exactly what North Korea wants.