The Battle of Breitenfeld was fought at a crossroads near Breitenfeld approximately 8 km north-west of the walled city of Leipzig on 17 September 1631. It was the Protestants' first major victory of the Thirty Years War. The victory confirmed Sweden's Gustavus Adolphus of the House of Vasa as a great tactical leader and induced many Protestant German states to ally with Sweden against the German Catholic League, led by Maximilian I, Elector of Bavaria, and the Holy Roman Emperor Ferdinand II.