Yet within a hundred years there arose a reaction in favour of the imperial idea--a reaction of which Germany was the apostle, which Italy accepted, which made many converts in West Francia. There were new and sufficient reasons for returning to the discarded system. The national hierarchies, who had undermined the Frankish Empire to broaden the foundations of ecclesiastical privilege and influence, were discovering that they had set up King Stork in place of King Log; the exactions of an Augustus were as nothing compared with the lawless pillaging of the new feudalism; and elective sovereigns, ruling by the grace of their chief subjects, were powerless for good as well as harm. The lower ranks of laymen had no better cause to be content with the new order under which the small freeholder was oppressed, the peasant enslaved, the merchant robbed and held to ransom. The freedom of the aristocracy spelled misery for every other class. These self-constituted tyrants passed their lives in devastating faction fights. Worst of all, their divisions and their absorption in petty schemes of personal aggrandisement left Europe at the mercy of uncivilised invaders. In the ninth and tenth centuries, medieval society experienced the same ordeal to which the Roman Empire had been subjected in the fifth. From the North and from the East a new generation of barbarians, perceiving the patent signs of weakness, began to break through the frontiers in search of plunder and of settlements. First came the Northmen from Norway and Denmark. Like the Saxons of the fourth century they were unrivalled seamen. Their fleets transported them from point to point faster than land forces could follow in pursuit; the great rivers served them as natural highways; and if beaten in a descent upon the land, they had always their ships as a safe refuge. To make treaties and to offer blackmail was a worse than useless policy; the Vikings came in bands which operated separately, or united in this year to scatter and form new combinations in the next. One leader could not bind another; to buy off one fleet was merely to invite the coming of a second. These pirates had begun to molest the British Isles and Frisia before the death of Charles the Great; but after the first partition of his Empire they fell on the whole coastline from the Elbe to the Pyrenees. Originally attracted by the hope of plunder they soon aimed at conquest; when, at the close of the ninth century, there was a sudden pause in the flood of armed emigration from the North, the Danelaw in England and Normandy on the opposite side of the Channel remained as alien colonies which the native rulers were obliged to recognise.