What happened to the acceptance rate of medieval currency during a war? For example, during the Hundred Years War, what would happen if a Frenchman tried to pay another Frenchman using English/Burgundian coins? Could the merchant refuse to take them since it's money from an enemy nation?
Excellent question!
There was certainly a risk that, during a war, currency from the opposing country might not be accepted as valid payment by the seller. This wasn’t 100% likely; it depended on the risk tolerance of the person you’re dealing with, because they might not be able to use that currency you paid them to pay other people, and it’s a whole cycle. There was certainly a risk that you would be charged a higher price in enemy currency than domestic currency.
So one option that the Frenchman would have is to go to a money changer like the Medici or really any foreign banker and exchange their suspect English or Burgundian coin for French currency or some other neutral currency for a fee.
Another possibility is to melt down the coins for their precious metal and then “sell” the raw gold or silver to the mint and get fresh new coins that were guaranteed to be good for paying “all debts public and private.” Once again, there would be a fee (charged as a difference between the value of gold and silver handed over and the value of gold or silver coins returned).
If you were feeling particularly bold, you could also just melt down the coins and counterfeit your own domestic currency, although if you got caught you would be executed in a particularly hideous fashion.
