The Byzantines employed a number of tactics, both overt and covert to achieve their aims through diplomacy rather than military force. It is therefore common to label Byzantine diplomacy as “war by other means” (Antonucci, 1993: 11). They were unique in their method of involvement in internal affairs of other countries. For this aim, the empire initiated a new institution for diplomatic practice, the Bureau of Barbarians. The correct answer is C.