The appalling carnage that has returned to the streets of Baghdad should cause shock, but little surprise. Most fingers of blame are pointing at the withdrawal of US troops from Iraq’s towns and cities at the end of June, now widely judged as premature. But, in truth, the black hole from which these savage killers keep crawling out is more about politics than security.

It was always going to be the case that Iraqi security forces would be tested to the limit and beyond, six years after an invasion and occupation that destroyed the state and disbanded the only significant national institution that predated Ba’ath party rule: the army. After the descent into a morass of insurgencies, rule by militia and vicious sectarian bloodletting, creating dozens of Saddam Husseins in place of one, how could it have been otherwise?