{44} The war against the Saxons and their conquest practically completed the unification of the German tribes on the continent, there remaining outside of the empire of Karl only the Scandinavian peoples in the north and the Angles and Saxons in England. By the conquest of the Saxons a vigorous race of pure German blood was added to the empire; their addition tended to increase the differences between the German and the Gallic portions of the empire, which was the natural basis of the division between France and Germany. The Saxons in the tenth and eleventh centuries were perhaps the chief race of the German kingdom, furnishing the rulers from the accession of Henry I in 919 to the death of Henry II in 1024. Karl's insistence upon the conversion of the Saxons to Christianity is in line with the policy of his predecessors to Christianize all the Germans. {45} The chief interest of this passage lies in the fact that it is the historical basis of the great French epic, the _Chanson de Roland_. Einhard mentions the death of three men in this attack as of special note; one of them was Hrotland, count of the mark of Brittany, the Roland of the poem. {46} The overthrow of Tassilo, duke of Bavaria, is a part of the policy of Karl to reduce the great duchies to control. In order to keep these outlying provinces in subjection and to govern them efficiently Karl divided them into counties over which he placed officials dependent directly upon himself and not upon a duke. This policy was carried out in Alamannia, Aquitaine, and Saxony as well, the purpose being to prevent the formation of independent power in the large divisions of the empire. It was successful under Karl, but later the civil wars among his descendants gave opportunity for the rise of similar great rulers in the same provinces (see nos. 24 and 25). {47} The Avars had come into Europe in the middle of the sixth century, along the Danube. After the Lombards moved into Italy the Avars occupied the whole Danube valley from Vienna to the mouth of the river. The kingdom of the Khan of the Avars probably included the remnants of the Hunnish empire and of the German tribes that had been subject to the Huns. {48} The kingdom of Gallicia and Asturia was one of the small Christian states in Spain composed of the former inhabitants that had retreated in large numbers to the mountains in the north and west at the time of the Mohammedan invasion (711-720). From these regions they later slowly won back the land from the Mohammedans. {49} Haroun-al-Raschid was Caliph of the Mohammedan world from 786-809, with his capital at Bagdad. His caliphate is the golden age of the Mohammedans reflected in the "Arabian Nights." The connection of Karl with Haroun and especially the negotiations mentioned here in regard to Jerusalem gave rise to the later legends concerning the crusades of Karl.