Octavian, who had emerged as the heir of Caesar and the leader of a faction, had successfully led his followers to a victory in a civil war that had eliminated all rivals: his faction could now be identiﬁed with the State. ‘Per consensum universorum potitus rerum omnium’: in these words he proclaimed his unchallenged and universal sovereignty, and the moral basis upon which he claimed that it rested.2 As long as this consensus continued to include the loyal support of the armies, Octavian was secure. But now that peace was established, how was he to act? If, like Sulla, he retired, civil war would ﬂare up once more; if he retained autocratic power, naked and unshamed, he might suﬀer the fate of Julius Caesar. He was thus faced with a most perplexing problem. In order to prevent the outbreak of internal disorders and to safeguard the empire against barbarian incursions, he must retain a uniﬁed military command in his own hands: to allow provincial commanders too much independence in the protection of the frontiers, would be to invite a repetition of the use that ambitious Republican proconsuls had made of their provincial commands to turn against the central government in Rome. Yet an autocratic military despotism would so outrage a ﬁve-hundred-year-old tradition of Republican government that it must lead ultimately to an explosion.