During a siege, a castle was surrounded by an enemy army. It prevented supplies from entering it and anyone inside from leaving it. Sooner or later, if the siege held, the castle inhabitants would be starved into surrender. Often, instead of waiting for the defenders to starve, the attackers set about forcing their way in to the castle by using a formidable array of siege weapons. They might also try a series of other tactics designed to weaken the castle's defences in some way, or even avoid the need for a costly and dangerous siege in the first place.

Spies

Besieging armies tried to recruit spies to help give them an advantage. Men posing as mercenaries (soldiers paid to fight) or local merchants or craftsmen who knew the castle well might be hired as spies. The besiegers were after information about how many people were inside the castle, where the weak spots in its defences were, how large its garrison was, how plentiful its supplies of food and water were, and how prepared the castle was for an attack.

Other siege tactics

If the spies revealed that additional troops were on the way to help defend the castle, the besieging army could organize an advance party to ambush them before they got there. If the lord was away from his castle, they might also attempt to capture him and hold him until he surrendered.

Local people, particularly women and children, would be encouraged to enter the castle. They would be no use to the defence of the castle, but at the same time would use up vital food and water. The defenders were much more likely to surrender if they were hungry and thirsty.

Supplies

A besieging army might often raid local farms and villages for provisions, destroying anything they did not need to prevent any supplies getting to the defenders in the castle. It was also essential to block any potential supply routes to the castle. Fixing a heavy chain across a river just below the water’s surface to snarl up boats was one way. Logs, chained together and studded with metal spikes, might be also strung between the banks.

Heralding the attack

Before battle commenced, it was standard practice to send a herald to announce the planned attack. If the castle’s lord thought the attacking forces were too great, he might send a messenger back to negotiate with their commander, and even surrender without a shot being fired.

Scaling the walls

Once the wooden hoardings on the battlements had been largely destroyed by fire and bombardment, the besieging army prepared to scale the walls. They could try climbing ladders, but these were easy to push away from the walls by the defending guards. Much more effective was a siege tower or belfry. The moat was filled in with logs and rubble and winching posts fixed in place. Teams of oxen hauled on ropes and the giant wooden “bear”, as the siege tower was sometimes called, draped with wet hides to protect it from catching fire, rumbled forwards. Under cover from its timber frame, the men clambered up a staircase and prepared to leap on to the castle battlements by means of a small drawbridge at the top.