As I remember, and this may have changed radically since, in the Open Devs each side had a numerical score of how much they wanted to start or continue the War, and in general it kept going down the longer the war dragged on. I believe at Zero your people basically stopped fighting and you lost or had to settle the war whether the gamer wanted to or not. I don't think I ever got to Zero so couldn't tell you what the actual mechanic was for the afflicted Faction. Point is, conquest had some extra problems built into it in Humankind that we are not used to in Civ. Even in Open Dev Lucy that didn't mean you couldn't conquer, just that you could not keep conquering indefinitely without pausing to Rebuild or gather strength and your population's resolve before starting on a rampage again. I've argued for 'supply lines' in 4X games before, and still think they could be added without cognitive overload, but they also aren't just a simple addition that can be slapped on at the end of the development process, so don't expect to see them in Initial Release Humankind or a Civ VI DLC. On the other hand, Humankind does put some 'supply-like' restrictions on your military. The lack of ability to rebuild units outside friendly territory is a big one, because within territory you can not only rebuild units over time, as in Civ, but also use Money to rebuild instantly: that means the Defender you just beat down to 20% last turn comes back next turn (potentially) at Full Strength while you are still at 50 - 75%. That's a HUGE bonus to the Home Field Advantage. Add to that having to send any reinforcements across the map, and the attacker needs some major tactical, technical, or numerical advantages to overcome the defender's advantages in 'supply' (access to replacements and reinforcements). It worked that way in Lucy Open Dev, at least, and I assume that's the way they want it to work: we may get confirmation nest week . . .