Final answer:
In the feudal system, lords promised their vassals protection, security, and peace in exchange for military service and other duties.
Step-by-step explanation:
The feudal system was a hierarchical structure that characterized medieval Europe, wherein lords granted land to their vassals in exchange for military service and other duties. These lands, known as fiefs, were cultivated by serfs, who in turn received protection and the means to live from the lords
Under this system, the lord had to promise his vassals three key things: protection, the provision of security, and maintenance of peace. This guaranteed the social order and mutual obligations of support between the different tiers of society, from the king down to the serfs.