The War of Metz or Four Lords' War was a feudal conflict which devastated the region around Metz between 1324 and 1326. At the Siege of Metz, in 1324, cannons were first recorded in Western Europe.
Following a series of quarrels with the city of Metz and mounting debts incurred by its bourgeoisie, King John of Bohemia, his uncle Baldwin, Archbishop of Trier, Count Edward I of Bar, and Duke Frederick IV of Lorraine joined together to form a coalition to take the city by force. The war was fought chiefly over the possession of land and the obligations, not always respected, of the burgesses as vassals of their lords. The debts the burgesses owed were many and varied:
After two years of trouble, Pope John XXII refused his financial assistance and the four princes were constrained to come to terms with the citizens of Metz. The treaty signed was called the "Peace of Herrings", as Metz was depending on herrings for food while the lords blocked incoming trade routes. The negotiations took place at Pont-à-Mousson. The burgesses promised not to set up markets on the fiefs of the lords without their consent.