Piling in

WHAT has been the worst mistake of Barack Obama’s presidency? Failing to plan for the day after intervening in Libya, says the president himself. Five years ago rebels backed by Western air strikes ousted Muammar Qaddafi, Libya’s dictator. But the West lost interest as the country stumbled on the path to democracy, then fell into civil war in 2014. Now Libya is divided, most notably between east and west, each with its own government, and home to three different branches of the Islamic State (IS) jihadist group.