In the period between 1300 and 1500 not every men-at-arms (fully armed and typically mounted soldier) was of the knightly class. At this time Knight was more of a social class associated with the richer landowning gentry. read more
All knights were men-at-arms, but not all men-at-arms were necessarily knights. Not all men-at-arms were even from noble families: many came from the younger sons of bourgeoisie and yeomanry. Knighthood was a title which had to be earned, not inherited or bought. read more
During the XIV-XVII centuries mercenaries were used to a significant degree, mostly as crossbowmen and shooters (since they were cheaper than "proper" soldiers and could be trained quickly; many served only for a season or two). read more