In GoT, and other European medieval set shows most cities have armed guards who act as a sort of police force and presumably army as well. How accurate is this? It was my understanding that most places didn't have a standing army and just recruited when needed rather than having professional soldiers. Or was it a case that they'd have a few professionals and recruit more as needed?
Let's say, kind of. More can always be said on the matter, so if anyone would like to contribute, don't let this post stop you! For the meantime, OP, here's a previous post from u/PartyMoses on the matter of guards.
On the matter of armies and their raising, we turn to the Medieval Armies Compilation. Two posts are most relevant as a general overview and because tag limit. If You Would Like To Know More, do tell me so's I can dig up some more out of the Compilation.