Fürstbistum Ermland
In the 13th century, during the Northern Crusades, the region of the pagan old Prussians had been conquered by the Monastic Order of the Teutonic Knights. In the 15th century, due to discontent with the Order's conduct, the Prussians revolted against them. In the Second Peace of Thorn, Royal Prussia became part of the Kingdom of Poland, although with special local privileges. Royal Prussia included the Prince-Bishopric of Warmia (Ermeland), which was surrounded on three sides by the Monastic state.