The siege warfare of the Middle Ages consisted of blockading the castle
in hopes of destroying it or taking it over for one’s own use. In peacetime
castles controlled the surrounding land, but when hostilities broke
out they provided passive resistance and served as a base of operations.
Constant skirmishing and outright warfare continued through the thirteenth
century and led to steady improvement in offensive weapons and
in castle design.
In the simplest terms, a lord and landholder secured his home with
walls whose height and thickness frustrated a direct assault. His enemies
could surround his castle and by cutting off supplies could hope to starve
him into surrender. Since armies were unreliable and men served only
for a specific period, the besiegers might simply go home to look after
their own affairs. In this situation, the defenders of a well-built and wellstocked
castle with a secure water supply had the advantage. In short,
the garrison relied on the passive strength of their castle’s high, thick
walls. They might make an occasional sally from a postern gate, but to
win, they had to rely on the defection of besieging troops or relief by the
arrival of a friendly army.