Though his object was undoubtedly peace, Augustus could not, of course, entirely escape war on his frontiers. He could not have finally settled the frontier on the line of the Danube, which was far the most valuable military work of his time, without wars which were both long and dangerous. It was absolutely necessary to cover Italy on the northeast, where the passes over the Alps are low and comparatively easy, and also to shield the Greek peninsula from attack by the wild tribes to the north of it. I have already alluded to the great work of Tiberius (the stepson of Augustus) in this quarter, which marks him as the third of the great generals who saved the civilisation of the Mediterranean for us. At one time Augustus thought of advancing the frontier from the Rhine to the Elbe, and so of connecting Elbe and Danube in one continuous line of defence. But this plan made it necessary to enclose all Germany west of the Elbe in the Roman Empire, and it was soon found that the Germans were not to be made into Roman provincials without a prolonged struggle for which Augustus had neither money nor inclination. So the frontier came back to the Rhine, and the Rhine and the sea marked the Roman frontier on north and west, until Claudius, the third successor of Augustus, added our island, or rather the southern part of it, to the Empire, in A.D. 43.
In the East Augustus contrived to do without war, trusting, and rightly trusting, to the enormous prestige he had won by overcoming Antony and Cleopatra, and annexing the ancient kingdom of Egypt. His fame spread to India, and probably even to China, with the caravans of merchants who then as now passed along fixed routes from Syria and Egypt to the Far East. We Britons know what _prestige_ can do among Orientals; it is a word that has often been in disfavour, but it means that there are ways of avoiding war without withdrawing just claims to influence. Augustus contrived on the strength of his prestige to keep an honourable peace with the Parthians and Armenians who bordered on the Empire along the line of the Euphrates, and his successors would have kept it too had they always followed out his policy. Tiberius, his faithful pupil and successor, did follow out that policy, and showed consummate skill in handling it.