It varied tremendously but the core fuedal requirement qas often the in return for land a noble owed their liege so many days of military service a year with a certain number and type of troops . Often one month . Obviously this was hugely impractical and few lieges could afford to pay their vassals to stick around but this is where scrutage comes in . Instead of heading off to fight you could instead pay your liege sufficient money for them to hire mercenaries to ' cover for you '. If carrying out any kind of expeditionary warfare it was not uncommon to only bring say 16 of your potential feudal levy , those who are really serious about fighting , then pay them with scrutage fees from the rest plus loot , your own reserves or loans . This was particularly common for England during the hundred years war and probably more responsible for lopsided victories than magic longbows , the more efficient English kings essentially had a full time army of professional men at arms and yeomen archers who were making careers out of fighting and looting . Most of the ' peasant archers ' at Agincourt were wearing better armour than anyone who was not a landed knight and were disciplined , experienced soldiers rather than conscripts .