The decline of the central power and the consequent rise [Sidenote: German divisions.] of a large number of semi-independent political units, each with a separate existence of its own, though held together by certain common duties and interests, make German history in this period peculiarly difficult and complicated. And the number of these units was far greater in the thirteenth century than would have seemed likely at an earlier date. The great duchies formed by the Karolings had, by the policy of subsequent rulers, been broken up or allowed to become extinct. The great duchy of Swabia, for instance, came to an end with the Hohenstaufen, and was never revived. But the extinction of each duchy brought with it an immense increase of the number of tenants-in-chief. Every noble, town, and even village which had previously held of the duke, now claimed to hold directly of the Emperor; and though many of the weaker units fell victims to the greed of powerful neighbours, yet some, like the original members of the Swiss Confederation, succeeded in retaining the coveted position. In Germany, too, primogeniture was in those days a rare exception, and the practice of equal partition among brothers necessarily led to a great increase in the number of princely tenants of the Emperor. It is, of course, impossible in this volume to attempt to [Sidenote: The lay princes.] trace the separate history of the various principalities and states which fill the rather ill-defined territory known as Germany. But it is necessary at starting to have a clear conception of some of the chief families which play so important a part in subsequent history. The four most prominent princely houses in the middle of the thirteenth century were those of Ascania, Welf, Wittelsbach, and Wettin. The first was sub-divided into two lines, descended from the two sons of Albert the Bear. The elder son had held the marks of Brandenburg in the north, which, since 1267, were split up among several brothers. The younger son, Bernard, had in 1180 received from Frederick Barbarossa the diminished duchy of Saxony, which was now held by his grandson, Albert II. (1261-1298). The great family of Welf, so powerful in the previous century, was now confined to the duchy of Brunswick, afterwards sub-divided into Lüneburg (Hanover) and Wolfenbüttel (Brunswick). The House of Wittelsbach was represented by two brothers, Lewis II., who combined the duchy of Upper Bavaria with the Palatine county (_Pfalzgrafschaft_) of the Rhine, and Henry, who held the duchy of Lower Bavaria. Henry of Wettin, whose descendants acquired Saxony in the fifteenth century and retain it to the present day, was at this time Margrave of Meissen and Landgrave of Thuringia. But the most powerful individual prince at this time was Ottokar, ruler of the Slav kingdom of Bohemia, which was brought by geography and history into close connection with Germany. To Bohemia, which he inherited in 1253 from his