Complex sentence: This security of military help was the primary reason the lord entered into the feudal relationship, but the vassal had another obligation to his lord, namely attendance at his court, whether manorial, baronial or at the king's court itself in the form of parliament.
Split into simpler sentences: This security of military help was the primary reason the lord entered into the feudal relationship. In addition, the vassal had another obligation to his lord, namely attendance at his court, whether manorial, baronial or at the king's court itself in the form of parliament.