Treaty of Warsaw
Following King Sigismund III's Prussian regency contract (1605) with Joachim Frederick of Brandenburg and his Treaty of Warsaw, 1611, with John Sigismund of Brandenburg, confirming the Brandenburgian co-inheritance of Prussia, these two regents guaranteed the free practice of Catholic religion in prevailingly Lutheran Prussia. Based on these contracts some Lutheran churches were reconsecrated as Catholic places of worship (e.g. St. Nicholas Church, Elbląg in 1612).