Up to the Thirty Years' War, the fortress was a secure stronghold—until it became the site of the 1636 Battle of Wittstock, when the troops of the Swedish Empire under Field Marshals Johan Banér and Alexander Leslie defeated the allied Imperial and Saxon forces under Elector John George I of Saxony. Followed by the outbreak of a plague epidemic two years later, Wittstock remained devastated and lost about half of its population.