The web is atwitter in response to North Korea's claim to have exploded a hydrogen bomb — essentially an atomic bomb on steroids — and the international community is wondering what to make of this latest development in Hermit Kingdom. Last month, the mercurial leader Kim Jong Un abruptly canceled the Beijing leg of the tour of his all-girl rock and roll band Moranbong; this month he's promising to up his Armageddon game. What should we make of this?...