Our sources for the constitutional settlement and division of the provinces in 27 B.C., and the modification of the settlement in 23 B.C., are notoriously brief and inadequate. Neither Augustus in the Res Gestae nor Velleius Paterculus mentions the provincial aspects of either settlement. The earliest source is Strabo (840): ‘(Caesar) δίχα διεῖλε πᾶσαν τὴν χώραν καὶ τὴν μὲν ἀπέδειξεν ἑαυτῷ τὴν δὲ τῷ δήμῳ (military provinces for himself, peaceful ones for the People)…ἑκατέραν δὲ τὴν μερίδα εἰς ἐπαρχίας διένειμε πλείους, ὡν αἵ μὲν καλοῦνται Καίσαρος, αἵ δὲ τοῦ δήμου. καὶ εἰς μὲν τὰς Καίσαρος ἡγεμόνας καὶ διοικητὰς Καῖσαρ πέμπει, διαιρѽν ἄλλοτε ἄλλως τὰς χώρας…εἰς δὲ τὰς δημοσίας ὁ δῆμος στρατηγοὺς ἤ ὑπάτους…(list of public provinces)…τὰς δὲ ἄλλας ἐπαρχίας ἔχει Καῖσαρ, ὧν εἰς ἃς μὲν πέμπει τοὺς ἐπιμελησομένους ὑπατικοὺς ἄνδρας,εἰς ἃς δὲ στρατηγικούς, εἰς ἃς δὲ καὶ ἱππικούς…’Then there is Suetonius (Div. Aug. 47) : ‘provincias validiores et quas annuis magistratuum imperiis regi nec facile nec tutum erat, ipse suscepit, ceteras proconsulibus sortito permisit.’ Finally there is the account in Cassius Dio (LIII, 12, 2–3): ‘τὴν μὲν φροντίδα τήν τε προστασίαν τѽν κοινѽν πᾶσαν ὡς καὶ ἐπιμελείας τινòς δεομένων ὑπεδέξατο, οὔτε δὲ πάντων αὐτòς τѽν ἐθνѽν ἄρξειν, οὔθ' ὅσων ἄν ἄρξῃ, διὰ παντòς τοῦτο ποιήσειν ἔφη, ἀλλὰ τὰ μὲν ἀσθενέστερα ὡς καὶ εἰρηναϊα καὶ ἀπόλεμα ἀπέδωκε, τὰ δὲ ἰσχυρότερα … κατέσχε, λόγῳ μὲν ὅπως ἡ μὲν γερουσία ἀδεѽς τὰ κάλλιστα τῆς ἀρχῆς καρπῷτο….’
These are the only accounts of the division of the provinces in 27. For the settlement of 23 our evidence is even poorer, a single sentence in Cassius Dio (LIII, 32, 5) ‘… τήν τε ἀρχὴν τὴν ἀνθύπατον ἐσαεἱ καθάπαξ ἔχειν ὥστε μήτε ἐν τῇ ἐσόδῳ τῇ εἴσῳ τοῦ πωμηρίου κατατίθεσθαι αὐτὴν μήτ' αὕθις ἀνανεοῦσθαι, καὶ ἐν τῷ ὑπηκόῳ τὸ πλεϊον τѽν ἑκασταχόθι ἀρχόνων ἰσχύειν ἐπέτρεψεν’.
The paucity of the sources—combined with the fact that they are mainly in Greek—has led to insoluble problems about how Augustus' position was described at the time, or (alternatively) what the nature of his imperium vis à vis the provinces was. None the less there is a fair consensus of opinion about the division of the provinces itself, and the nature of the administrative pattern which it produced. This can be summarized as follows:
Augustus undertook the administration of a large provincia, comprising Spain, Gaul and Syria, for a period of ten years, possibly with proconsular authority. He governed these provinces through legati appointed by, and responsible to, himself. The other provinces were governed by pro-magistrates responsible to the Senate. Down to 23 Augustus was also consul. In 23, while retaining his provincia, he abandoned the consulate and accepted imperium mains, which gave him superior authority to pro-magistrates, and enabled him to intervene outside his provincia when necessary. In normal circumstances, however, control of the provinces was divided between the Emperor and the Senate.