The Thirteen Years' War (Polish: wojna trzynastoletnia; German: Dreizehnjähriger Krieg), 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.
After the defeat suffered by the Teutonic Order at the Battle of Grunwald (Tannenberg) in 1410 and the ensuing political, military and economic problems, the state was rife with internal conflict between the ruling Order and the local Prussian nobility. Eventually, this tension led to an uprising by the Prussian Confederation representing the Prussian nobility and cities, who sought the protection of the Polish King Casimir IV Jagiellon. Once the King granted his assent, war broke out between the Prussian Confederation, supported by Poland, and the proponents of Teutonic Knight rule.