I created some world where a civilization just 100 years more advanced than our fights a world war with something like a noble "horde" which utilizes slavery, but is very cautious about killing innocent lives. Ofc slave soldiers don't count as killing. The good guys usually don't have such moral obligations.
Also most of the world doesn't know a war since at least 90 years and the horde is after a civil war from which they became very advanced in terms of warfare and one warrior is very hard to be killed by anyone. At one moment they control or vassalize 80% of land surface of a planet, but theu are stopped by some China-America like industrial superpower who overproduces dumber weapons plus the horde's weapons are hackable by some technician who was from outside because the horde was backwards in terms of STEM. The end is just like end of nazis, but without Soviets starting cold war.
