African leaders are stepping up their response to Boko Haram, with Chadian soldiers chasing the militants from a northern Nigerian town and the African Union calling for a 7,500-member regional force to tackle what it called “a serious threat” to the continent. A communiqué adopted by the peace a...

BANKI, Nigeria — The soldiers arrived in the middle of the night, tearing through the village of Nigerian refugees, barging into stick huts where families slept in knots on the floor. For years, those refugees had been on the run from Boko Haram insurgents, finally escaping across a dried riverbed...