The citizens of Magdeburg had turned Protestant in 1524 and joined the Schmalkaldic League against the religious policies of the Catholic emperor Charles V in 1531. During the Schmalkaldic War of 1546/47, the Lower Saxon city became a refuge for Protestant scholars, which earned it the epithet "Herrgotts Kanzlei" (), but also an Imperial ban that lasted until 1562. The citizens refused to acknowledge Emperor Charles's Augsburg Interim and were besieged by Imperial troops under Maurice, Elector of Saxony in 1550/51.