What was the most important role of nobles during the middle ages?

Answer 1

In theory the job of the nobility in the middle ages was war. The noble gained his land from a greater noble by pledging military service, and gained the submission of his peasantry by being able to provide military protection and justice to the lower classes.

In practice things were not so simple. As the Middle Ages advanced things became more complex. Grants of land, which were initially given as loyalty rewards, became inheritable from one generation to the next. Not every member of an aristocratic family was necessarily suited in skill and temperament for military service. Also, many soldiers were drawn from the common classes and paid a salary. which required funding. As time passed an increasing number of noble land holders were able to substitute monetary payments for physical military service to their lord. These payments, known as scutage, were in turn used to hire soldiers or to employ landless knights who were essentially mercenaries or warriors for higher. This was far from universal, many aristocrats continued to do military service, but there was also a significant number that never took full knighthood and paid their way out of military service and became essentially a gentry class.