The serments ("oaths") were confraternities of cross-bowmen, archers, and swordsmen formed in the Middle Ages whose members swore oaths to provide military services to the dukes of Brabant. The earliest and most famous was the Grand Serment des Arquebusiers de Saint-Georges (Grand Oath of the Crossbowmen of Saint George), which dates from the 13th century. Headquartered at the Halle au Pain (Broodhuys), the group was open to all citizens in good standing, but numbers were limited by decree to 60 men. Employed by Duke John I n 1301 against rebels in Mechelen, they were granted land in recognition of their service in the Sablon district in 1304. In 1346, Duke John III authorized the members to transport in procession the statue of the Virgin Mary, believed to be miraculous, to Notre-Dame du Sablon. Every year an archery competition was held next to the church, the winner declared to be the roi ("king") of the serment. Archduchess Isabella won the event in 1615.
There were four additional serments: the Petit Serment de Saint-Georges (1381), the Serment des Archers de Saint-Sébastien et de Saint-Antoine (1422), the Serment des Arquebusiers de Saint-Christophe (1477), and the Serment des Escrimeurs de Saint-Michel (1480).
Historical Dictionary of Brussels. Paul F. State.