The Aeneid celebrates Augustus and the greatness of Rome, and for that reason many read it as the official poem of the empire, but the text also sustains the opposite reading: it lays out the price of empire in lives, and the question has no single answer.
Much speaks for the official reading. Jupiter promises the Romans an empire "without limit of space or of time." In Book 6, Anchises shows Aeneas "Augustus Caesar, son of a god," who will found again the golden ages in Latium, and states Rome's mission: rule the peoples, spare the conquered, and beat down the proud. In Book 8, the shield ends at Actium, with Augustus at the stern and the Penates beside him, and in the triumph that consecrates three hundred temples.
There is also what the official reading does not explain. In the same parade in which Anchises shows the future Romans, he warns against the civil war of Caesar and Pompey, and the review ends with the young Marcellus, whom the fates will take early, while Anchises asks for flowers for his soul. The shield decides no combat, and the hero carries it without understanding. Cato, the opponent of Caesar, Augustus's adoptive father, appears giving laws to the just. Dido's curse gives poetic origin to the enmity between Rome and Carthage. And the poem ends with the victor killing a surrendered man who asked for his life in the name of an aged father.
The formula "spare the conquered and beat down the proud" serves as the measure of good dominion and as the justification of every conquest, and the text does not separate the two. That is why readers remain divided: the poem gives Augustus his future and says in verse what its price is.