After the 1637 death of the last Pomeranian duke, Bogislaw XIV, Köslin passed to his cousin, Bishop Ernst Bogislaw von Croÿ of Kammin, and fell to Brandenburg-Prussia after the Treaty of Westphalia in 1648.
After the 1637 death of the last Pomeranian duke, Bogislaw XIV, Cöslin passed to his cousin, Bishop Ernst Bogislaw von Croÿ of Kammin. Occupied by Swedish troops during the Thirty Years' War, the city was granted to Brandenburg-Prussia after the Treaty of Westphalia in 1648.