The first thing that Conan — or Locke Lamora, or Grey Mouser, or Vimes, or a D&D party — would notice about a real medieval city would be the almost total absence of an Ankh Morpork-style town watch.
It’s a stock trope: here come a dozen
Keystone Cops town watch in their funny armour, to arrest the drunken barbarian or catch the thief. Only it’s not like that in reality, or at least not quite like that in Later Medieval and Early Modern England, France, and Germany.
That’s not a criticism. Fantasy writers must write what they will. Dickensian thief takers are plausible, and raise themes to do with policing and justice. However, if, like me, you write Historical Adventure Fiction , then you need to know how policing worked because integrity, and because somebody else will know and will gleefully correct you in reviews. (It’s funny when your research is better than theirs though — and the one time I ever answered a review.)
It’s actually quite hard to drill down to D&D level details about the medieval past. Scholars are usually more interested in the development of legal systems and local authority than what happens when Conan gets into a brawl. However, there are a few useful sources: This PhD thesis on trial by battle; The Time Traveller’s Guide to Medieval England: A Handbook for Visitors to the Fourteenth Century (link); The Martial Ethic in Early Modern Germany: Civic Duty and the Right of Arms (link); plus various more antiquarian tomes on my research shelf.
And, there are some surprises beneath the crust of sometimes dry text. Let’s kick off with what every aspiring thief and rogue needs to know…