But with this vigorous effort, piracy was not extirpated: on the contrary, the Danish coasts were themselves ravaged the following year by the Slavonians. This disaster was owing to the anger of Henry the Lion, duke of Saxony, who had sent a contingent to the corps of Valdemar. He had probably not expected the reduction of Rugen; he certainly was jealous of his ally’s success; and, to provoke a breach, he demanded half of the treasures, of the captives, of the hostages, and of the tribute stipulated to be paid. There was probably some justice in the demand; but the king refused to comply with it, and Henry, in great anger, informed the Slavonians that they might consider themselves at liberty to inflict whatever injuries they could on the Danes. How this prince had acquired so great an ascendency over these people; how they came to call themselves his vassals, is one of those problems which history cannot solve. There must have been treaties, and marriages, and conquests, which chroniclers have omitted. The fact of his ascendency is indisputable. “He was the only prince on earth,” says Helmold, “that could put a bridle into the mouth of that ferocious people, and direct it at his pleasure.” The vast restless tribes, from Courland to Mecklenburgh, wanted only this stimulus to rise; and they did rise, in numbers too formidable to be resisted. Valdemar and his ministers suffered the tide to roll on: they had the mortification to witness its ravages on their shores; but when it had spent a portion of its fury, they raised an armament, cleared their shores, passed into the Baltic, and, after some advantages, carried the war into the Vandalic territories.[151] But what salutary impression could be made on a people who, at the approach of an enemy, plunged, with their substance, into the impenetrable recesses of their forests, and returned the moment that enemy retired? Jomsberg, indeed, one of the most flourishing maritime cities in Europe, was taken, and its great treasures became the prize of the victors; but the place had been taken before by Canute the Great in 1010, and Magnus the Good in 1044. No sooner was it demolished, than it began to rise from its ruins. Valdemar therefore perceived that, as he could not exterminate these numerous tribes, who often acted in a general confederation, and were always ready to descend upon his coasts, his only hope was in the friendly interference of the Saxon duke. He therefore met that sovereign, conceded all his demands, and had the satisfaction to see Henry issue his mandate, that the Danish coasts should no longer be molested. For some years they were not; but a very precarious surety was that which depended on the will of another person—a person who might, at any moment, change his policy, or whose influence might be destroyed by death.