The chapter of Ermeland, at the time when he became a member of it, was the centre of a violent political struggle, in the decision of which Copernicus himself was called on to act a considerable part. In the latter half of the fifteenth century, a bitter war was carried on between the King of Poland and a military religious fraternity, called the Teutonic or German Knights of St. Mary of Jerusalem, who were incorporated towards the end of the twelfth century. Having been called into Prussia, they established themselves permanently in the country, built Thorn and several other cities, and gradually acquired a considerable share of independent power. On the death of Paul von Segendorf, bishop of Ermeland, Casimir, king of Poland, in pursuance of a design which he was then prosecuting, to get into his own hands the nomination to all the bishoprics in his dominions, appointed his secretary, Stanislas Opporowski, to the vacant see. The chapter of Ermeland proceeded notwithstanding to a separate nomination, and elected Nicolas von Thungen. Opporowski, backed by Casimir, entered Ermeland at the head of a powerful army. From this period the new Bishop of Ermeland necessarily made common cause with the German Knights; they renounced their allegiance to the crown of Poland, and threw themselves on the protection of Matthias king of Hungary. At length, Casimir finding himself unable to master the confederacy, separated Nicolas von Thungen from it, by agreeing to recognise him as Prince-Bishop of Ermeland, on the usual condition of homage. Nicolas thus became confirmed in his dignity, but his unhappy subjects did not fare better on that account, the country being now exposed to the fury of the German Knights, as it had suffered before from the violence of the Polish soldiery. These disturbances were continued during the life of Luke Watzelrode, and the city of Frauenburg, as well as its neighbour Braunsburg, frequently became the theatre of warlike operations. The management of the see was often committed to the care of Copernicus during the absence of his uncle, who on political grounds resided for the most part at the Court; and his activity in maintaining the rights of the chapter rendered him especially obnoxious to the Teutonic Order. In one of the short intervals of tranquillity, they took occasion to cite him before the meeting of the States at Posen, on account of some of his reports to his uncle concerning their encroachments. Gassendi, who mentions this circumstance, merely adds that at length his own and his uncle’s merit secured the latter in the possession of his dignity. In 1512 Watzelrode died, and Copernicus was chosen as administrator of the see until the appointment of the new bishop, Fabian von Losingen. In 1518 the knights under their grand master, Albert of Brandenburg, took possession of Frauenburg and burnt it to the ground.