The Catholic League was a coalition of Catholic states of the Holy Roman Empire formed 10 July 1609. While initially formed as a confederation to act politically to negotiate issues vis-à-vis the Protestant Union, modelled on the more intransigent ultra-Catholic French Catholic League (1576), it was subsequently concluded as a military alliance "for the defence of the Catholic religion and peace within the Empire".
Mural in Donauwörth in memory of the Kreuz- und Fahnengefecht
Foundation of the Catholic League, 1870 painting by Karl von Piloty
Maximilian I, Duke of Bavaria
Frederick V of the Palatinate as King of Bohemia
The Protestant Union, also known as the Evangelical Union, Union of Auhausen, German Union or the Protestant Action Party, was a coalition of Protestant German states. It was formed on 14 May 1608 by Frederick IV, Elector Palatine in order to defend the rights, land and safety of each member. It included both Calvinist and Lutheran states, and dissolved in 1621.
Document establishing the Protestant Union signed 14 May 1608, now in Bavarian State Archive (Bayerische Hauptstaatsarchiv)