Most Crusader castles were designed to resist armed attack by large forces for a considerable length of time. The builders who constructed them were keenly aware of the weapons available to the assailants and tried to devise ways of countering them. The development of castle architecture must be seen as the result of a continuing dialectic between attack and defence which gave the advantage sometimes to one, sometimes to the other. Only by examining techniques of attack can we come to a real understanding of the architecture of defence.

The most basic way of taking a castle was by blockade and starvation of the defenders; simply by surrounding the place and preventing anyone getting in and out famine would complete the task at minimum risk to the attacking army. In practice, forcing surrender in this way was usually impractical and it could only be achieved in special circumstances. The problems for the attacking army were numerous. To begin with, it was not only the defenders who had to eat; the besieging army had to be supplied and this often caused major problems. When the Crusaders blockaded Muslim-held Antioch through the grim winter of 1097–8, their forces suffered terribly from hunger and they were forced to send off foraging parties further and further into the already ravaged countryside; even so, famine among them almost caused the collapse of the whole project. The defenders, by contrast, seem to have been comparatively well provided for and it was treachery, not starvation, which finally led to the fall of the city.