Article by Arms Control Wonk Jeffry Lewis on how far the DPRK has miniaturized its warheads and the role that nuclear testing plays in this development.
“When North Korea’s first test in 2006 produced a very disappointing yield, many of us took the small yield to be confirmation of this general hypothesis—North Korea had tried to skip directly to a compact device and it did not work. At one point, a reporter told me this was also the working hypothesis within the US intelligence community. Since then, North Korea has conducted two more nuclear tests that produced far higher yields—a few kilotons in 2009, followed by several kilotons in 2013. Following that lest test, the North Koreans announced they had “miniaturized” their nuclear devices. It seems very plausible to me that, after three tests, the North Koreans have a nuclear weapons design somewhere in the Mark 12 to March 7 range—450-750 kg in mass with a diameter between 60-90 cm.”