With the Roman invasion there came to the future British race a benefit from both those causes. The comparative ease of the conquest by the Roman Power, holding as it did the mastery of the seas, freed the ensuing settlement by the conquerors from a good deal of the bitterness which would have followed a desperate resistance. The Romans were generous winners and good colonists. Once their power was established firmly, they treated a subject race with kindly consideration. Soon, too, the local pride of the Britons affected their victors. The Roman garrison came to take an interest in their new home, an interest which was aided by the singular beauty and fertility of the country. It was not long before Carausius, a Roman general in Britain, had set himself up as independent of Italy, and with the aid of sea-power he maintained his position for some years. The Romans and the Britons, too, freely intermarried, and at the time when the failing power of the Empire compelled the withdrawal of the Roman garrison, the south of Britain was as much Romanised as, say, northern Africa or Spain. Thus from the very dawn of known history natural position and climate marked out Britain as the vat for the brewing of a strenuous blood. The sea served her "in the office of a wall or of a moat defensive to a house" to keep away all but the most vigorous of invaders. The charm and fertility of the land made it certain that a bold and vigorous invader would be tempted to become a colonist and not be satisfied with robbing and passing on. With the decay of the Roman Empire, and the withdrawal of the Roman legions to the defence of Rome, the Romanised Britons were left helpless. Civilisation and the growth of riches had made them at once more desirable objects of prey, and less able to resist attack. The province which Rome abandoned was worried on all sides by the incursion of the fierce clans of the north and the west. A decision, ultimately wise, judged by its happy results, but at the moment disastrous, induced some of the harried Britons to call in to their aid the Norsemen pirates, who at the time, taking advantage of the failing authority of Rome, were swarming out from Scandinavia and from the shores of the Baltic in search of booty. The Angles, the Saxons, the Jutes, were willing enough to come to Britain as mercenaries, even more willing to stay as colonists. An Anglo-Saxon wave swept over the greater part of England, and was stopped only by the mountains of Wales or of Scotland. That was the end of the Britons as the chief power in Britain, but they mingled with their conquerors to modify the Anglo-Saxon type with an infusion of Celtic blood. In the mountainous districts the Celtic blood continued to predominate, and does to this day.