At the same moment when the Roman commonwealth was practically changed into a monarchy, the Roman dominion was thus brought, not indeed to its greatest extent, but to an extent of which its further extension was only a natural completion. ♦Conquests under Augustus and Tiberius.♦ There seems a certain inconsistency when we find Augustus laying down a rule against the enlargement of the Empire, while the Empire was, during his reign and that of his successor, extended in every direction. But the conquests of this time were mainly conquests for the purpose of strengthening the frontier; the occasional changes of this and that city or district from the dependent to the provincial relation, or sometimes from the provincial to the dependent, are now hardly worth mentioning. ♦Incorporation of the dependent kingdoms.♦ Between Augustus and Nero, or, at all events, between Augustus and Vespasian, all the dependent states in Asia and Africa, such as _Mauritania_, _Kappadokia_, _Lykia_, and others, were finally incorporated with the Empire to which they had long been practically subject. These annexations can hardly be called conquests. And it was merely finishing a work which had been begun two hundred years before, when the small corner of Spain which still kept its independence was brought under the Roman power. ♦Strengthening of the frontier.♦ The real conquests of this time consisted in the strengthening of the European frontier. No frontier nearer than the Rhine and the Danube could be looked on as safe. This lesson was easily learned; but it had also to be accompanied by another lesson which taught that the Rhine and the Danube, and no more distant points, were to be the real frontiers of Rome.