ABSTRACT
The backbone of the frontiers of mainland Europe was formed by the two great rivers, Rhine and Danube. That this is so was not a matter of policy, of ambition successfully achieved; it came about by default. The Roman vision in the early days of the empire was for conquest of the entire world as it was then known, and this is what Augustus, the first princeps, the first general with supreme power to operate ‘world-wide’, set out to achieve, campaigning eastwards from the Rhine and planning a major expedition beyond the Danube. But this vision of Imperium sine fine, of world domination, came up against the realities of geography, in Europe the existence of a vast and inhospitable landmass across which tribes moved, the trend of whose advance was in a southerly and westerly direction, the direction of Rome. In retrospect it is possible to see that the turning point in Europe lay very early in the imperial period, well within the reign of Augustus himself, when his plans for conquest beyond Rhine and Danube were shattered by the Illyrian revolt of AD 6 and the Varus disaster of AD 9; the emperor lost his nerve and Rome lost the initiative. Though subsequent emperors would campaign beyond the two great rivers and incorporate new lands into the Empire the advances made were of no great size; nor were they very long lived. Their major significance lay in the improved communications they brought about between east and west, the Danubian and the Rhineland provinces. For much of their length and for most of the period the two rivers formed the boundary of Rome's European provinces, marking the limit of empire; but rivers do not make good frontiers. They may be bureaucratically convenient, providing clear lines of demarcation as long as the peoples on both sides agree to observe them, but they are lines which are difficult to enforce, they are militarily weak; they are highways which unite, not barriers which divide.
