This January, few experts took much notice of the Iraqi army’s difficulties in retaking Falluja from Islamist terrorists. But when Islamic State of Iraq and the Levant (ISIS), as these jihadis called themselves, captured Mosul, Iraq’s second largest city, on 10 June after just three days of fighting, the world did notice and it was afraid. Since Mosul fell, ISIS has spread terror across western, central and northern Iraq, coming dangerously close to Baghdad itself in early October. In July ISIS’s elusive leader, Abu Bakr al-Baghdadi, briefly emerged in Mosul to proclaim himself caliph of the so-called Islamic State, thereby eclipsing the gnarled bosses of al-Qaeda as ‘the strongest horse’ on the Islamist scene. Based on the erasure of the border between Iraq and Syria, ISIS has mesmerised would-be jihadists everywhere, while other Islamist terror groups have paid homage to al-Baghdadi.

The UN’s human rights supremo has quite accurately described ISIS as the marriage of genocidal nihilism with modern social media. The latter amplify images of the mass murder of Shia prisoners that recall the Nazi Einsatzgruppen. In one video, prisoners were shown being shot in the head and shoved into