The period from the death of Conrad IV. to the election of Rudolph of Habsburg in 1273 is generally called the Great Interregnum, and it was used by the princes to extend their territories and to increase their authority. On several occasions it had seemed as if the German crown would become hereditary, but it had been kept elective by a variety of causes, among them being the jealousy of the Papacy and the growing strength of the aristocracy. In theory the election of each king needed the sanction of the whole of the immediate nobles, but in practice the right to choose the king had passed into the hands of a small but varying number of the leading princes. During the 13th century several attempts were made to enumerate these princes, and at the contested election of 1257 seven of them took part. This was the real beginning of the electoral college whose members at this time were the archbishops of Mainz, Cologne and Trier, the duke of Saxony, the duke of Bavaria, who was also count palatine of the Rhine, the margrave of Brandenburg and the king of Bohemia. After this event the electors became a distinct element in the state. They were important because they could maintain the impotence of the crown to check disorder by imposing conditions upon candidates for the throne, and by taking care that no prince powerful enough to be dangerous to themselves should be elected to this position.
Until the time of the interregnum the territories of a prince were rarely divided among his descendants, the reason being that, although the private fiefs of the nobles were hereditary, their offices--margrave, count and the like--were in theory at the disposal of the king. There was now a tendency to set this principle aside. Otto II., duke of Bavaria, a member of the Wittelsbach family, had become by marriage ruler of the Rhenish Palatinate, and after his death these extensive lands were ruled in common by his two sons; but in 1255 a formal division took place and the powerful family of Wittelsbach was divided into two branches. About the same time the small duchy of Saxony was divided into two duchies, those of Wittenberg and Lauenburg, the former to the south and the latter to the north of the great mark of Brandenburg, and there were similar divisions in the less important states. It was thus practically settled that the offices and territories, as well as the private fiefs, of the princes were hereditary, to be disposed of by them at their pleasure. This being thoroughly established it would have been hard, perhaps impossible, even for a sovereign of the greatest genius, to reassert in anything like its full extent the royal authority. The process of division and subdivision which steadily went on broke up Germany into a bewildering multitude of principalities; but as a rule the members of each princely house held together against common enemies, and ultimately they learned to arrange by private treaties that no territory should pass from the family while a single representative survived.