Once more Frederick crossed the Alps. He had crushed his formidable cousin, Henry the Lion, and banished him from Germany; he had turned the truce with the Lombards into the Peace of Constance by acquiescing in the loss of the imperial rights for which he had fought. His eldest son, Henry, had been crowned King of Germany as long ago as 1168. Frederick was now anxious to secure for him the succession to the imperial title, and hoped to find the Pope willing to crown Henry as his father's colleague in the Empire. But although Lucius III, Alexander's successor (1181-5), had been driven from Rome, and was dependent on the Emperor's help, it was impossible for him or for any Pope to agree to Frederick's wish. Two emperors at once were a manifest absurdity, and Frederick was not likely to accept the Pope's suggestion that he should resign in favour of his son. Moreover, there lay between Pope and Emperor the still unsettled question of the inheritance of the Countess Matilda. It was clear that the quarrel must shortly be renewed. By the nature of the respective claims there could never be more than a temporary truce. Lucius died, but his successor, Urban III, was yet more irreconcilable. Meanwhile Frederick had resolved on an act which would make the breach between Papacy and Empire irreparable. The King of Sicily was William II "the Good." His marriage to a daughter of Henry II of England (1177) had proved childless, and the succession seemed likely to fall to Constance, daughter of King Roger and aunt of the reigning King. She was over thirty years of age. Frederick's defeat in 1174 had been due to his failure to divide his enemies. Now, however, he had his chance. The Lombards, having got all that they wanted, were quite favourable to him. He planned to win Sicily also by a marriage between his youthful son Henry and the almost middle-aged heiress Constance. A party in Sicily helped him; and the marriage and the coronation of the happy pair as King and Queen of Italy took place at Milan in January, 1186. Not only had the Emperor knocked away the staff upon which the Papacy had been disposed to lean its arm for more than a century; but he had actually picked it up and proposed to use it in the future for the purpose of belabouring the Popes. Moreover, he had really secured his object of a hereditary empire; for Henry, now King with his father in Germany and in Italy, must needs succeed to all the paternal honours. In vain Urban tried to raise up a party against the Emperor; and the sentence of excommunication, which at length he had determined to pronounce, was stopped only by the death of the Pope on October 20, 1187. [Sidenote: Frederick's death.]