Christian of Oliva

At least Christian was able to establish the Diocese of Chełmno east of the Vistula, adopting the episcopal rights from the Masovian Bishop of Płock, confirmed by both Duke Konrad and the Pope.

Duke Konrad of Masovia still was not capable to end the Prussian attacks on his territory and in 1226 began to conduct negotiations with the Teutonic Knights under Grand Master Hermann von Salza in order to strengthen his forces.

Meanwhile, von Salza had to abandon his hope to establish an Order's State in the Burzenland region of Transylvania, which had led to an éclat with King Andrew II of Hungary.

He obtained a charter by Emperor Frederick II issued in the 1226 Golden Bull of Rimini, whereby Chełmno Land would be the unshared possession of the Teutonic Knights, which was confirmed by Duke Konrad of Masovia in the 1230 Treaty of Kruszwica.

Bishop Christian continued his mission in Sambia (Samland), where from 1233 to 1239 he was held captive by pagan Prussians, and freed in trade for five other hostages who then in turn were released for a ransom of 800 Marks, granted to him by Pope Gregory IX.