Schill said France could engage a division of 20,000 troops within 30 days to operate as part of an allied coalition. Paris, he added, would be able to command a force of around 60,000 soldiers made up of French and other allied troops. The French army comprises some 121,000 soldiers, with 24,000 reservists.
It matters in terms of international law and such, I think. IIRC mercenaries aren’t protected by law and don’t require certain treatments