Treaty of Warsaw
Following King Sigismund III's Prussian regency contract (1605) with Joachim Frederick of Brandenburg and his Prussian enfeoffment contract (Treaty of Warsaw, 1611) with John Sigismund of Brandenburg these two rulers of Ducal Prussia guaranteed free practice of Catholic religion in prevailingly Lutheran Prussia. Based on these contracts Prince-Bishop Szymon Rudnicki of Ermland/Warmia achieved the restitution of St. Nicholas as Roman Catholic parish church in 1612, then the only one in Elbing, and remaining a Catholic church since.