Maximilian's successor was his son, Rudolph II., who had been chosen king of the Romans in October 1575, and who in his later years showed marked traces of insanity. The new emperor had little of his father's tolerant spirit, and under his feeble and erratic rule religious and political considerations alike tended to increase the disorder in Germany. The death of the Calvinist leader, the elector palatine Frederick III., in October 1576 and the accession of his son Louis, a prince who held Lutheran opinions, obviously afforded a favourable opportunity for making another attempt to unite the Protestants. Under the guidance of Augustus of Saxony a Lutheran confession of faith, the _Formula concordiae_, was drawn up; but, although this was accepted by 51 princes and 35 towns, others--like the landgraves of Hesse and the cities of Magdeburg and Strassburg--refused to sign it, and thus it served only to emphasize the divisions among the Protestants. Moreover, the friendship between the Saxon and the Palatine houses was soon destroyed; for, when the elector Louis died in 1583, he was succeeded by a minor, his son Frederick IV., who was under the guardianship of his uncle John Casimir (1543-1592), a prince of very marked Calvinist sympathies and of some military experience. Just before this time much unrest in the north-west of Germany had been caused by the settlement there of a number of refugees from the Netherlands. Spreading their advanced religious views, these settlers were partly responsible for two serious outbreaks of disorder. At Aix-la-Chapelle the Protestants, not being allowed freedom of worship, took possession of the city in 1581. The matter came before the diet, which was opened at Augsburg in July 1582, but the case was left undecided; afterwards, however, the _Reichshofrat_ declared against the insurgents, although it was not until 1598 that Protestant worship was abolished and the Roman Catholic governing body was restored. At Cologne the archbishop, Gebhard Truchsess von Waldburg, married and announced his intention of retaining his spiritual office. Had this proceeding passed unchallenged, the Protestants, among whom Gebhard now counted himself, would have had a majority in the electoral college. The Roman Catholics, however, secured the deposition of Gebhard and the election in his stead of Ernest, bishop of Liége, and war broke out in 1583. Except John Casimir, the Protestant princes showed no eagerness to assist Gebhard, who in a short time was driven from his see, and afterwards took up his residence in Strassburg, where also he instigated a rebellion on a small scale. Thus these quarrels terminated in victories for the Roman Catholics, who were successful about this time in restoring their faith in the bishoprics of Würzburg, Salzburg, Bamberg, Paderborn, Minden and Osnabrück. Another dispute also ended in a similar way. This was the claim made by the administrator of the archbishopric of Magdeburg, a Hohenzollern prince,