Thirteen Years' War: The Secret Council of the Prussian Confederation sends a formal act of disobedience to the Grand Master of the Teutonic Knights, sparking the Thirteen Years' War.

The Thirteen Years' War, also called the War of the Cities, was a conflict fought in 1454–1466 between the Prussian Confederation, allied with the Crown of the Kingdom of Poland, and the State of the Teutonic Order.