A person became a vassal by pledging political allegiance and providing military, political, and financial service to a lord. A lord possessed complete sovereignty over land or acted in the service of another sovereign, usually a king. If a lord acted in the service of a king, the lord was considered a vassal of the king. As part of the feudal agreement, the lord promised to protect the vassal and provided the vassal with a plot of land. This land could be passed on to the vassal's heirs, giving the vassal tenure over the land.