Chlothar, with his diminished royal prerogative, seems to have had neither the opportunity nor the power to engage in wars of conquest beyond the bounds of his realm. [Sidenote: Samo and the Slavs.] He had to look on, without stirring, while a great, if ephemeral, kingdom was built up beyond his eastern frontier. Behind the Thuringians and Bavarians, on the Elbe and Oder, there had dwelt for the last two hundred years, since the German races had migrated westward, a group of small and disunited Slavonic tribes, calling themselves Wiltzes, Sorbes, Abotrites, and Czechs. Their dissensions had kept them from being dangerous neighbours till the time of Chlothar. But about 620 a Frankish adventurer, named Samo, who had gone eastward, half as trader half as buccaneer, united many of the Slavonic tribes, and became their king. He gradually extended his power all down the valley of the Elbe, on both sides of the Bohemian mountains, and was soon to prove himself a serious trouble to the realm of the Merovings. Towards the end of his reign, Chlothar II. made his son Dagobert king of Austrasia, while he was still a very young man. The chief councillors by whose aid Dagobert administered his realm were two men whose names form a landmark in Frankish history—Arnulf, bishop of Metz, and count Pippin the elder, the ancestors of the great house of the Karlings. [Sidenote: St. Arnulf and Pippin the elder.] Bishop Arnulf was the wisest and best of the prelates of Austrasia, and, after a long life of usefulness in church and state, won the name of saint by laying down his crozier and ring and retiring to a hermitage, to spend his last fifteen years in the solitudes of the Vosges. Count Pippin, a noble from the land between Meuse and Mosel, whose ancestral abodes are said to have been the manors of Hersthal and Landen, was appointed mayor of the palace, and lived in the closest concord and amity with Arnulf. They cemented their alliance by a marriage, Begga, the daughter of Pippin, being wedded to Ansigisel, the son of the bishop; for Arnulf, like many of the Frankish clergy, lived in lawful wedlock. From these parents sprang the whole of the line of mayors, kings, and emperors whose mighty deeds were to make their comparatively unimportant ancestors famous in history.