A number of military experts – including the defense secretary, James Mattis – have warned that a US war against North Korea would be hard, incredibly destructive and bloody, with civilian casualties in the millions, and could go badly for US forces. But Lt. Gen. Herbert Raymond McMaster, President Trump’s national security adviser, is apparently insistent that ‘a military strike be considered as a serious option’. One of Gen. McMaster’s claims to fame is a Silver Star he was awarded for a tank ‘battle’ he led in the desert during the so-called Gulf War of 1991. As a young captain leading a troop with nine new Abrams M1A1 battle tanks, McMaster destroyed 28 Iraqi tanks in 23 minutes without losing any of his own or suffering any casualties. McMaster’s exploit (later embellished with a name, the ‘Battle of 73 Easting’) was little more than a case of his having dramatically better equipment.

Not long after the Second World War, the scientists at Los Alamos realised that they could vastly improve the design of a nuclear bomb, making it light enough to fly on a rocket.

Last month North Korea carried out its fourth nuclear test. As with the previous test, three years ago, the yield was equivalent to between six and nine kilotons of TNT. Yet while the first three tests were undoubtedly atomic bombs – the explosive energy came from the fission of the nucleus of plutonium-239 – this time North Korea announced that it had tested a hydrogen bomb. An H-bomb’s energy comes from the fusion of the nuclei of the hydrogen isotopes deuterium and tritium. Whereas A-bombs attain yields measured in kilotons, H-bombs typically attain megaton yields. They are also known as thermonuclear bombs because the nuclei must be heated to a temperature as hot as the centre of the sun in order to initiate the fusion process.

On Christmas day at 3.05 p.m. I managed to see The Interview. It was not so easy. It was playing at the Cinema Village, a pocket size three-screen theatre in Greenwich Village which specialises in obscure foreign films and other exotica. When I showed up at 2.30 all performances were sold out except the 1 a.m. but I joined the standby line and just at 3.03 managed to get in and find a seat in the very back of the theatre. There were some TV people outside both when I entered and left. What they expected I have no idea.