That decline in the numbers killed by terrorism in the west ensured the problem received only sporadic attention in the US and Europe. But, in the rest of the world, the number of lawless areas in which jihadi militias can freely operate and train has increased.

A decade ago, the main area of concern for western counter-terrorism efforts was Afghanistan and the border areas of Pakistan — with Somalia another significant worry. But now the self-styled Islamic State of Iraq and the Levant (Isis) controls a large swath of Syria and Iraq, including Mosul, Iraq’s second-largest city.

In Africa, Boko Haram — possibly inspired by the success of Isis — has also seized territory and now controls a part of northern Nigeria the size of Belgium, as well as threatening neighbouring states such as Cameroon and Niger. Much of Libya has slipped into violent anarchy and jihadism is also endemic in Yemen.

The obvious questions are why the problem is escalating and what needs to be done. In the solipsistic world of US politics, it is natural for politicians to assume the problem somehow begins in Washington. Democrats cite President Bush’s decision to invade Iraq. The Republicans claim President Obama withdrew from Iraq prematurely.