On Christmas Day, U.S. forces unleashed targeted missile and drone strikes in Nigeria against Islamist terrorists who had been killing Christians and other civilians with impunity. It propelled Nigeria into the headlines and caught many Americans unaware of the growing conflict in Africa between Christians, radical Islam, and others that is spreading across the sub-Saharan Sahel region. But I had just been on a fact-finding mission to Nigeria a week earlier and, although U.S. Africa Command?s kinetic action was a surprise, it was not entirely unexpected. In November, President Donald Trump had made...