They were intended to keep the restless population of Fes el-Bali (the old city) under control as much as to actually defend the city from external attacks.[2][3] Accordingly, the forts were built in commanding positions overlooking the city, from which their canons could easily bombard the city if desired.[2] The Saadians built Borj Nord, Borj Sud, and three bastions along the south and east walls of Fes el-Jdid to emulate Portuguese military architecture; a consequence of their wars to oust the Portuguese from Morocco.[3][4] Their construction was probably helped by the labour and expertise of European prisoners captured in the famous Battle of the Three Kings in 1578.[4] These are the first and arguably only fortresses in Fez designed for the new age of gunpowder.[3]