Military. - There were two types: Offensive & Defensive

a)      Offensive

The castle was primarily a base from which the lord and his armed horsemen could control the surroundings countryside. Castles and knights, the unique products of feudal society, thus went together, the latter forming a heavy cavalry and a military elite. The range of the castle was the range of the horse, some ten miles if one returned the same day.

      Dover Castle, Kent