Answer:
Be ready to defend his vassal's territory as part of a "standing army".
Explanation:
Feudalism came after the fall of Rome, the main classes in feudal society were royalty, the nobility, the clergy, and commoners (peasants, labors). The knights in the feudal social class society, a low-ranking noble, trained to fight with heavy armoured. The Knights were to protect their vassal's from the enemies. Knights were granted land for their services to the kings and nobles.