A castle was usually so placed that, even if an army could pass by without being hurt by a sortie, when it had passed, it would need supplies and therefore the supplies would be cut off, if the castle was still in enemy hands, because carts drawn by oxen and defended by only few men would be an easier target for a ...

In medieval warfare, armies could rarely afford to "ignore" a castle because it functioned as a strategic military "checkmate" on the surrounding landscape. A castle was not just a house; it was a fortified base for a garrison of knights and soldiers who could ride out and attack an invading army's supply lines, forage parties, and messengers—a tactic known as "sallying." If an invader simply marched past, they would leave a hostile, well-armed force at their rear, capable of cutting them off from reinforcements or escape routes. Furthermore, castles served as the administrative and financial hubs of a region; capturing the castle meant capturing the machinery of government and the local treasury. To control the land, you had to control the castle. Ignoring it meant the local lord could continue to collect taxes, raise new troops, and signal allies for help. Consequently, an invader usually had two choices: a costly and time-consuming siege to starve the garrison into submission, or a risky direct assault. Only by neutralising the castle could an army truly claim to have conquered the territory.