A little history about the role and name of the sergeant. Sergeants were originally, during the [middle ages], [professional soldiers] who fought as knights but held no noble title. That is: In armour, mostly on horseback and in formation. They were mostly [mercenaries] who filled up the nobles' ranks in combat and trained the forces held by the nobility. This is where the [NCO]'s role as an [instructor] comes from. In a time when the only professional soldiers were [mercenaries] or [nobles], there was little time to train the rallied forces or [militia]. The sergeants took it upon them to train the infantry and nobility in warfare. The ancient picture of a sergeant standing behind a formation of pressed [infantry] -holding a lance too keep them in place comes from this time. During the [reconquista] and during the [crusades] sergeants fought with the knights of different orders and kings. Indeed the term sergeant became a rank in some of the orders of the [Holy Land].

Sergeant (essay)