The German Catholic League was initially a loose confederation of Roman Catholic German states formed on July 10, 1609 to counteract the Protestant Union

Protestant Union

The Protestant Union or Evangelical Union was a coalition of Protestant German states that was formed in 1608 to defend the rights, lands and person of each member....

 (formed 1608), whereby the participating states concluded an alliance "for the defence of the Catholic religion and peace within the Empire." Modeled loosely on the more intransigent ultra-Catholic French Catholic League (1576), the German Catholic league initially acted politically to negotiate issues with the slightly older Protestant Union.

Nevertheless, the league's founding, as had the founding of the Protestant Union, further exacerbated long standing tensions between the Protestant reformers

Protestant Reformation

The Protestant Reformation was a 16th-century split within Western Christianity initiated by Martin Luther, John Calvin and other early Protestants. The efforts of the self-described "reformers", who objected to the doctrines, rituals and ecclesiastical structure of the Roman Catholic Church, led...

 and the members of the Catholic Church which thereafter began ratcheting upwards with ever more frequent episodes of civil disobedience, repression, and retaliations that would eventually ignite into the first phase of the Thirty Years' War

Thirty Years' War

The Thirty Years' War was fought primarily in what is now Germany, and at various points involved most countries in Europe. It was one of the most destructive conflicts in European history....

 roughly a decade later with the act of rebellion and calculated insult known as the Second Defenestration of Prague on 23 May 1618.