Perhaps as important as any of these internal elements of dissolution was that ever-present and ever-developing external menace, the growing power of the barbarian nations. The position of any nation in the historical scale always depends largely upon the relative positions of its neighbour states. Rome early subjugated the other Italian states and then in turn, Sicily, Carthage, and Greece. She held a dominating influence over the nations of the Orient; or, at least, if they held their ground on their own territory, she made it impossible for them to think of invading Europe. Meantime, at the north and west there were no civilised nations to enter into competition with her, much less to dispute her supremacy. For some centuries the peoples of northern Europe could be regarded by Rome only as more or less productive barbarians, interesting solely in proportion as they were sufficiently productive to be worth robbing. But as time went on these northern peoples learned rapidly through contact with the civilisation of Rome. They were, in fact, people who were far removed from barbarism in the modern acceptance of the term. It is possible (the question is still in doubt) that they were of common stock with the Romans; and if their residence in a relatively inhospitable clime had retarded their progress towards advanced civilisation, it had not taken from them the racial potentialities of rapid development under more favourable influences; while, at the same time, the very harshness of their environment had developed in them a vigour of constitution, a tenacity of purpose, and a fearless audacity of mind that were to make them presently most dangerous rivals. It was during the later days of the commonwealth and the earlier days of the empire that these rugged northern peoples were receiving their lessons in Roman civilisation--that is to say, in the art of war, with its attendant sequels of pillage and plundering.[2] Those were hard lessons which the legions of the cæsars gave to the peoples of the north, but their recipients proved apt pupils. Even in the time of Augustus a German host in the Teutoberg Forest retaliated upon the hosts of Varus in a manner that must have brought Rome to a startling realisation of hitherto unsuspected possibilities of disaster.