Richard Rouget,  a gun for hire over two decades of bloody African conflict, is the unlikely face of the American campaign against militants in Somalia.

A husky former French Army officer, Mr. Rouget, 51, commanded a group of foreign fighters during Ivory Coast’s civil war in 2003, was convicted by a South African court of selling his military services and did a stint in the presidential guard of the Comoros Islands, an archipelago plagued by political tumult and coup attempts.