But this constitutes his only real service to Germany. While he was enjoying the peaceful and prosperous development of Naples and Sicily, his great empire in the north was practically taking care of itself, for the boy-king, Henry, governed chiefly by allowing the reigning bishops, dukes and princes to do very much as they pleased. There was a season of peace with France, Hungary and Poland, and Denmark, which was then the only dangerous neighbor, was repelled without the Imperial assistance. Frederick II., in his first rivalry with Otto, had shamefully purchased Denmark's favor by giving up all the territory between the Elbe and the Oder. But when Henry, Count of Schwerin, returned from a pilgrimage to the Holy Land, and found the Danish king, Waldemar, in possession of his territory, he organized a revolt in order to recover his rights, and succeeded in taking Waldemar and his son prisoners. Frederick II. now supported him, and the Pope as a matter of course supported Denmark. A great battle was fought in Holstein, and the Danes were so signally defeated that they were forced to give up all the German territory, except the island of Rügen and a little strip of the Pomeranian coast, beside paying 45,000 silver marks for the ransom of Waldemar and his son. [Sidenote: 1230.] About this time, in consequence of the demand of Pope Innocent III. that all heresy should be treated as a crime and suppressed by force, a new element of conflict with Rome was introduced into Germany. Among other acts of violence, the Stedinger, a tribe of free farmers of Saxon blood, who inhabited the low country near the mouth of the Weser, were literally exterminated by order of the Archbishop of Bremen, to whom they had refused the payment of tithes. In 1230, Gregory IX. wrote to king Henry, urging him to crush out heresy in Germany: "Where is the zeal of Moses, who destroyed 23,000 idolaters in one day? Where is the zeal of Elijah, who slew 450 prophets with the sword, by the brook Kishon? Against this evil the strongest means must be used: there is need of steel and fire." Conrad of Marburg, a monk, who inflicted years of physical and spiritual suffering upon Elizabeth, Countess of Thuringia, in order to make a saint of her, was appointed Inquisitor for Germany by Gregory, and for three years he tortured and burned at will. His horrible cruelty at last provoked revenge: he was assassinated on the highway near Marburg, and his death marks the end of the Inquisition in Germany.