The danger posed by North Korea’s nuclear weapons programme has ramped up faster than anyone predicted, demonstrated by its test of an intercontinental ballistic missile last month. An assessment from the Defense Intelligence Agency suggesting that the hermit kingdom has successfully miniaturised a nuclear warhead is equally frightening. The regime of Kim Jong Un poses a deadly serious and increasing threat to the security of its neighbours, the US and the world.

US president Donald Trump has responded in recent days with rhetoric of almost unprecedented aggressiveness. “North Korea best not make any more threats to the United States — they will be met with fire and fury like the world has never seen,” he said. The words seem to deliberately echo President Harry Truman’s comments on the eve of the Nagasaki bombing, promising “ruin from the air, the like of which has never been on this earth”.

Pyongyang responded that it was “examining?.?.?.?a plan for making an enveloping fire at the areas around Guam” — a US territory and home to a US military base. Mr Trump, in turn, sent tweets describing the power of the US nuclear arsenal, and retweeted a news story about the readiness of US forces in Guam for a “fight tonight”.