In 1230 the Catholic monastic order of the Teutonic Knights launched the Prussian Crusade. The campaign, that was supported by the forces of Polish duke Konrad I of Masovia, initially intended to Christianize the Baltic Old Prussians, succeeded primarily in the conquest of large territories. The order, emboldened by imperial approval, quickly resolved to establish an independent state, without the consent of duke Konrad. Recognizing only papal authority and based on a solid economy, the order steadily expanded the Teutonic state during the following 150 years, engaging in several land disputes with its neighbors. Permanent conflicts with the Kingdom of Poland, the Grand Duchy of Lithuania, and the Novgorod Republic, eventually led to military defeat and containment by the mid-15th century. The last Grand Master Albert of Brandenburg converted to Lutheranism in 1525 and turned the remaining lands of the order into the secular Duchy of Prussia.