2.2 Imperium as power: Augustus and the beginning of the empire

The basic meaning of the Latin term imperium was ‘command’ and the term included the authority that lay behind the mandate. During the long period in which Rome was a republic, imperium signified the power attached to the office of the leading elected magistrates of the city, notably the two annual consuls and the lower-ranking praetors. It was the consuls who commanded the armies and went to the provinces assigned them by the senate. Praetors too came to share a military function as the territory controlled by Rome increased and they were appointed to administer provinces.

But over time additional mechanisms were evolved which extended imperium to other individuals in special circumstances. One was the ancient office of dictator which gave supreme control to a single senior magistrate in times of particular need; but in the mid and late republic this title was given only twice, once to Sulla in 81 BC and then to Julius Caesar, who was appointed dictator several times from 49 BC, and life-long dictator before his death in 44 BC. A second procedure which was regularly used was the extension of a magistrate's imperium to cover the year following his tenure of office. This created pro-magistrates such as pro-consuls and pro-praetors who were also often involved in managing the provinces. Very occasionally imperium could be granted to an individual who was not a magistrate to deal with some exceptional situation.

Imperium, then, was the basis of real authority and military clout. The issues of who wielded this power and how became of urgent importance in the first century BC, since it had become clear by then that the established administrative mechanisms of the republic were inadequate to deal with the problems brought by territorial gains. The careers of Pompey the Great (Gnaeus Pompeius Magnus) and Julius Caesar both reflect a strong tension between the exercise of real power and the constitutional need to contain it within a proper base. Pompey had been granted military commands and triumphs without ever being a magistrate, and when he eventually became consul in 70 BC it was because he had forced the senate to let him skip the earlier stages on the conventional ladder of magistracies. Outside Rome he came to gain extraordinary power and influence in the east, where he had defeated King Mithridates of Pontus and was courted by many local rulers wishing to gain recognition. Perhaps even more significant for the development of the later empire were the activities of Julius Caesar in the period after Pompey's death in 48 BC. Holding consulships and the dictatorship, he embarked on reforms which addressed some major problems to do with the administration of the provinces. Honours were heaped on him, and although he was aware of the need to keep within the bounds of republicanism, his behaviour as a virtual monarch led to his assassination in 44 BC. He is often described as being, in effect, the first Roman emperor. It is clear that after him there was no possible going back to the broader power base that the republic (theoretically at least) entailed. This momentum lay behind the developments which culminated in the battle of Actium in 31 BC. After that Augustus (or Octavian, to use the name modern scholars give him at this stage in his career [Goodman, p. 33]) came to take full military control of Rome and its territories. But it was in his skilful manipulation of the existing constitutional structures of the republic that ‘empire’ was set up for the first time.

As well as military control, Augustus needed a legitimate base from which to exercise imperium. This could not be the office of dictator given the resentment it provoked in the case of his great-uncle Julius Caesar. Instead he looked for an arrangement that would be constitutionally valid, and at the same time give him a special place from which he could work with other groups in Rome whose continued support was obviously necessary for the control of the vast territory. The result was a settlement in 27 BC whereby the senate invested Augustus with a consul's imperium from which to govern his huge provinda (province). (Like imperium, the Latin word provinda has a dual meaning in terms of ‘place’ and ‘sphere of command’.) Augustus was now technically a magistrate in the time-honoured republican tradition, and later added the powers of other offices to this, gradually assuming their imperium for the single person of the ruler. Thus he could claim that he was operating within Rome's established framework of magistracies, but with a significant difference: in recording his achievements in Res Gestae 34 he describes that ‘I surpassed everyone in influence but I had no more power than others who were my colleagues in the different magistracies’. (Res Gestae is a vast inscription in which Augustus recorded his achievements as a type of autobiographical epitaph.) This sums up his vision: his power (potestas) was constitutionally no more than that of his colleagues in office, but it was his influence (auctoritas), derived from this combination of magistracies, that gave him supremacy. Writing a century or so later, the historian Tacitus related: ‘Augustus, using the title princeps, took the whole state worn out with the troubles of civil war into his imperium’ (Annals 1.1).

It was at this time, then, that imperium was transformed from the broad-based practices of the republic to the ultimate authority of a single ruler. Augustus favoured the title princeps because of its republican connotations (meaning ‘first man’ or ‘a prominent statesman’) rather than dictator or the authoritarian dominus, so his rule is often described as ‘the principate’. But from now on the term imperium Romanum was also increasingly used in ancient sources. It was the start of the Roman Empire.