Early on, manning a castle was a feudal duty of vassals to their magnates, and magnates to their kings, however this was later replaced with paid forces. A garrison was usually commanded by a constable whose peacetime role would have been looking after the castle in the owner's absence. Under him would have been knights who by benefit of their military training would have acted as a type of officer class. Below them were archers and bowmen, whose role was to prevent the enemy reaching the walls as can be seen by the positioning of arrowslits.