In 1174, when Frederick made his fifth expedition to Italy, the Lombard league had been formed, and the fortress of Alessandria raised to check his progress. The campaign was a complete failure. The refusal of Henry the Lion to bring help into Italy was followed by the defeat of the emperor at Legnano on the 29th of May 1176, when he was wounded and believed to be dead. Reaching Pavia, he began negotiations for peace with Alexander, which ripened into the treaty of Venice in August 1177, and at the same time a truce with the Lombard league was arranged for six years. Frederick, loosed from the papal ban, recognized Alexander as the rightful pope, and in July 1177 knelt before him and kissed his feet. The possession of the vast estates left by Matilda, marchioness of Tuscany, and claimed by both pope and emperor, was to be decided by arbitration, and in October 1178 the emperor was again in Germany. Various small feuds were suppressed; Henry the Lion was deprived of his duchy, which was dismembered, and sent into exile; a treaty was made with the Lombard league at Constance in June 1183; and most important of all, Frederick's son Henry was betrothed in 1184 to Constance, daughter of Roger I., king of Sicily, and aunt and heiress of the reigning king, William II. This betrothal, which threatened to unite Sicily with the Empire, made it difficult for Frederick, when during his last Italian expedition in 1184 he met Pope Lucius III. at Verona, to establish friendly relations with the papacy. Further causes of trouble arose, moreover, and when the potentates separated the question of Matilda's estates was undecided; and Lucius had refused to crown Henry or to recognize the German clergy who had been ordained during the schism. Frederick then formed an alliance with Milan, where the citizens witnessed a great festival on the 27th of January 1186. The emperor, who had been crowned king of Burgundy, or Arles, at Arles on the 30th of July 1178, had this ceremony repeated; while his son Henry was crowned king of Italy and married to Constance, who was crowned queen of Germany.