Nothing therefore could be more timely for his plans than the invitation from the Prince of Mazovia, who in 1225 sent envoys to Herman; especially since the order had just been deprived in Transylvania of lands given to support it while warding off heathen Kumanians. The envoys offered the Teutonic master Culm and some adjoining lands for the order, in return for curbing the Prussians. Herman resolved to accept, should the Emperor prove friendly to the offer. He hastened to Frederick at Rimini, explained the whole question, received a grant in which Konrad's endowment was confirmed; besides the order was given all the land it could conquer and make subject to the Emperor alone. The grand master's next care was to obtain papal approval. Two envoys from Herman were sent to Poland, where they obtained, as the chronicles of the order relate, a written title to Culm and the neighboring land as well as to all Prussia which they could conquer. Near Torun (Thorn) a wooden fortress was built, called in German Fogelsang (Bird-song). This fortress was the first residence of the knights, who later on had so much power and such influence in the history of Poland. Only two years later did Herman send his knights to Culm. One of the first acts was to purchase for various considerations, from the Bishop of Plotsk and from Christian, the Bishop of Prussia, their rights over the lands granted them in Culm. The labor of conversion began, and soon the grand master prevailed on the Pope to proclaim throughout Europe a crusade against Prussia. From Poland alone came twenty thousand men, and many more from other parts of Europe. When the knights had made a firm beginning of work, their design of independence was revealed. They wished to be rid of even a show of submission to the Prince of Mazovia. They raised the question by trying to incorporate the remaining Brothers of Dobjin, and thus acquire the grant given them by Konrad. They had disputes also with Bishop Christian and the Bishop of Plotsk. In 1234 the Bishop of Modena was sent as papal legate to settle the disputes. The legate decided, to the satisfaction of the bishops, that of all lands won from the Pagans two thirds were to be retained by the knights and one third given to the bishops, the church administration being under the order in its own two thirds. For the Prince of Mazovia nothing was left, though he asserted sovereign rights in Culm and Prussia, and would not permit the order to acquire the grant given the Brothers of Dobjin by incorporating the remaining members of that body.