The siege of Tortosa was part of a decade of intense activity by Louis against the Umayyads in the region of Catalonia. Following Louis's capture of Barcelona in 801, the southern boundary of Carolingian dominion was the river Llobregat, while the northern boundary of the Umayyads was the Ebro. The land between became a violent and depopulated frontier zone. Tortosa was the most important Umayyad fortification on this frontier and effectively the furthest Umayyad outpost in Catalonia.