"My vassal's vassal is not my vassal" refers to the feudal master-slave relationship without mutual obligations between vassals and lords

The castle is the basic core of Western European feudal society , but between the highest royal power and the lowest serfs, there is not only one layer of lords, but several levels. Each lord can divide his territory into several pieces and seal them to his subordinates, thus forming a A pyramid-shaped ladder network. A large lord is a vassal relative to the king or emperor, and the king and emperor are his lords. But relative to the small and medium-sized nobles entrusted by the great lord, he is a lord, and the people entrusted by him are lords. They are his vassals; and so on, down to the lowest level of ordinary knights. Lords and vassals at all levels bear responsibilities and obligations to each other according to the contract. In continental Europe, usually a vassal was only responsible to his immediate lord, forming the so-called principle of "my vassal's vassal is not my vassal".

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