In my setting, the entire known world is clinging to the side of a humongous nearly vertical cliff. Living space is a kind of commodity since there aren't many cliff benches large enough to build a city upon, which wouldn't be suited better for growing crops instead. So most cities are limited in growth and width, mostly extending by carving galleries in the surrounding cliffs once all available horizontal space has been filled.
To add to that, prior to the invention of airships (current technology level is ~1850s-1900s with few bits of technobabble allowing for steampunk-y details, but nothing ridiculous like steam-powered robots) the only possible mode of travel was by either using discovered passages and caves which rarely were wider than several meters, or by constructed road-bridges. I'm currently on the fence about should I include or omit rideable flying creatures, but it's unlikely they will be a thing, for now.
There is a species of sapient flying creatures though, on roughly the same level of technological development as humans, but they are less numerous, and both civilizations are trying to not infringe on each other's territory, and "birds" rarely have any significant population in the cities of humans (Humans just can't live in the "bird" cities at all, since they weren't built with flightless inhabitants in mind).
Magic sort of exists in this setting (it's complicated), but it isn't common or reliable enough (You, basically, don't have any way to replicate its effects or teach others how to perform it, nor is there any "genes that make you able to do magic" so there are no wizards or witches in a conventional fantasy sense) to become a mundane part of the society.
I guess all of this severely limits the size of the army one can reasonably wield or employ to attack others. No fields where one can do epic infantry battles of our middle ages, and almost every passage is a handy impassable defensive position and a chokepoint simultaneously. How would that affect the warfare in such a world, before airships showed up on stage and changed all the rules?