President Idriss Deby of Chad said on Wednesday he knew the whereabouts of Abubakar Shekau, the leader of the Nigerian militant group Boko Haram, and called on him to surrender or risk being killed. Chad's army has waged a series of battles against Boko Haram as part of a cross-border military campaign and has re-taken territory the militant group held in northeastern Nigeria. ... The Chadian army is considered one of the best in the region, backed by a strong air force. It first deployed to help Cameroon fend off Boko Haram and is now pressing southwest into Nigerian territory...