Such were some of the methods by which the Romanisation of Gaul was effected, and the foundations so well and truly laid that through all the invasions of Franks and Burgundians, Gaul remained Roman in speech and thought, and remains so to this day.[46] Of all the momentous problems which Augustus had to face, the delimitation of the northern frontier was the weightiest. It has always been one of the disputed questions of Roman history, why Augustus, who was generally so cautious and so unwilling to embark upon adventures, deliberately chose to cross the Rhine and plunge into those impenetrable forests of whose dangers and difficulties Julius Cæsar had left so clear a warning. Was it his aim to forestall the danger of a German invasion of Gaul? On the other hand, the Rhine might well seem a sufficient frontier, as indeed for many centuries it was. Was it his aim to exercise his troops in difficult warfare and perhaps secure military renown for the young men whom he had destined for the succession? These are scarcely adequate motives for a man like Augustus. Did he hope to acquire wealth out of Germany as he had done out of Gaul? He must have known that the virgin forests and undrained morasses of Germany would scarcely balance the difficulties and dangers of a campaign there, and that the Germans were far behind their Gallic cousins in civilisation. The problem seems to me insoluble unless we accept the theory that the whole scheme was part of the search for a natural strategic frontier undertaken with false notions of geography. It is certain that many of the ancients believed that they would find the Ocean again where Russia is, and that the Caspian Sea was part of it. In that case the Romans may have hoped to round off their empire satisfactorily in this direction. It would explain the curious tactics by which Roman expeditions crossing the Rhine and plunging into the heart of Germany ordered their fleets to coast along the Dutch and Danish shores. From whatever motives it was undertaken, this penetration of Germany and its ultimate failure was a fact of vast consequence in the history of Europe. From one point of view the history of Europe may be described as a record of the various relations between the Roman and the German elements, with occasional incursions from the Celtic or Turanian fringes. It is one long contest between Latin and Teutonic race, religion, language, law, and ideas political and economic. Hence it is impossible to overrate the importance of the moment when the first round of that age-long contest was fought out and settled. Hidden among the forests in those mysterious wildernesses beyond the Rhine were the numerous tribes who were destined one day to form the nations of Europe. Here were the Saxons of Saxony and England, the Swabians, the Franks, the Vandals, the Burgundians, the Goths, the Lombards, and many others, yet unnamed, the germs of the nations.