|The capture of the French king John II at Poitiers in 1356 (Source: Wikipedia)|
This interesting article appeared today on the BBC website. It seems that there was a system involved which governed what happened to prisoners of war in the Medieval period, and that it could be a lucrative source of income for those doing the capturing. Also of note is the fact that a captive could be taken back to their home in order for the ransom to be paid.
Treasure is always an good incentive for play in fantasy RPGs, and the idea behind this system shows that it could be possibly adapted as a set of rules. Aspiring adventurers could always develop it as an interesting sideline to their adventures and campaigns.