 In 1440 the anti-Teutonic Prussian Confederation was founded, and among its founders were cities of the Chełmno Land, including Toruń, Chełmno, Grudziądz and Brodnica.In 1454 the confederation started an uprising against the Teutonic Order and turned to Polish King Casimir IV Jagiellon with a request to include the region to Poland.The king agreed and signed the incorporation act, after which the Thirteen Years' War broke out.