Nine years after Timbuktu welcomed them as liberators, French troops are withdrawing from their final outpost in Mali's north. There are no cries of mission accomplished: the jihadist radicals who scattered when French-led forces intervened in 2013 have long since morphed into a low-intensity insurgency with raids as far away as the far north of Benin. With the summer's chaos in Afghanistan still fresh in memories, when is the right time to end a military intervention?