The Thirty Years' War ends with signing of the Peace of Westphalia in Osnabrück and Münster. The horrors of the war left deep traces in all regions of Brandenburg. From this time onwards Catholic, Lutheran and Reformed confessions have equal rights in the realm. 
As part of the Peace of Westphalia, the already largely Lutheran Prince-bishopric of Minden is secularised and placed under the authority of the Electorate of Brandenburg.