Dio’s account of the second century AD, the ‘Antonine period’ broadly construed, has not received the same attention when compared with the better-preserved Julio-Claudian books or the exciting contemporary narrative of the Severan age. This chapter examines Dio’s portrayal of five second-century emperors: Trajan, Hadrian, Marcus Aurelius, Commodus and Pertinax. It focuses particularly on the role that military qualities (or lack thereof) played in the historian’s assessment of their character and reigns. In Dio’s view, the best emperors were not necessarily the best generals, but leaders who were able to maintain the frontiers in the face of foreign threats and kept the troops disciplined and ready for defence at all time. A good emperor should be an all-rounder, able to balance attention to military matters with concern for the civilian government of the empire. In the second-century narrative, it is Marcus Aurelius who best embodies these qualities.