The vacant duchies of the Guelfs were disposed of on conditions that mark an epoch in the territorial development of Germany. Saxony, the last stronghold of the sentiment of the ancient four peoples of Germany, now underwent the same fate that had fallen to Bavaria earlier in Frederick’s reign. The western parts, including the vast dioceses of Cologne and Paderborn, were erected into the new duchy of Westphalia, and granted to the Archbishop of Cologne, Frederick’s ally. The lands between the Weser and the Elbe went to the chief of the lay enemies of the Guelfic house. Bernard of Anhalt, the son of Albert the Bear, received this district, along with the ducal title, but only on condition that the counties and bishoprics that in Henry the Lion’s days had been directly dependent on the Saxon duke, should henceforward hold immediately of the Empire. In the south the aged Welf VI. had quite withdrawn from politics, and Otto of Wittelsbach, Count-Palatine of Bavaria, the strenuous upholder of Frederick’s policy in Italy, was before long invested with the duchy of Bavaria, over which his descendants still bear rule. The fall of the Guelfs, the one family strong enough to rival the throne, compensated in some measure for Frederick’s failures in Italy. By the partition of Saxony and Bavaria, the last danger to the monarchy from the national duchies was removed. [Sidenote: Diet of Mainz, 1184.] In the great Diet of Mainz, held in 1184, the glories of the Diet of Besançon were renewed, after which the Emperor went over the Alps for his sixth and last visit to Italy. So strong did Frederick still feel himself, that he yielded to the importunities of Henry of England, and allowed Henry the Lion to return to Germany. [Sidenote: Union of Sicily with the Empire.]