In the 7th century, probably around 639, Saint Audomar (Saint Omer) established the bishopric of "Terwaan" or "Terenburg", the diocese of Thérouanne, which during the Middle Ages controlled a large part of the left bank of the river Scheldt. Territorially it was part of the county of Artois which belonged to the county of Flanders. In 1303 the town was burnt by Flemish forces during the Franco-Flemish War.