Final answer:
The higher lords and king promised protection and land-grants, known as fiefs, to the less powerful lords, or vassals, in return for their loyalty and military service in the feudal system.
Step-by-step explanation:
In the feudal system, the less powerful lords, known as vassals, would pledge loyalty and military service to the higher lords and the king. In exchange, the higher lords and the king promised protection and land-grants, or fiefs. The vassals could then extract wealth from the land to support their own needs, which typically included sustaining their equipment and retinue for war. The relationship was based on this mutual exchange of service for land and protection, with the vassals providing military aid and counsel, while the higher lords ensured security and justice for their subordinates, forming a stabilizing structure in the politically fragmented society of medieval Europe.