In his Nobel Peace Prize acceptance speech four-and-half years ago, when the United States was still fighting George W Bush’s battles against al-Qaida, Barack Obama spoke not so much about peace as the necessity of sometimes going to war. “Evil does exist in the world,” Obama remarked. “A nonviolent movement could not have halted Hitler’s armies. Negotiations cannot convince al-Qaida’s leaders to lay down their arms.”

Seemingly out of nowhere, that pragmatic vision of the world has now turned back to Iraq. A well-organized and blood-thirsty group of insurgents, Islamic State in Iraq and the Levant (Isis), is on the march. They may soon be headed for Baghdad.

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