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.