Welcome, friend.
BattleCoreRules (BCR) is designed to simulate large-scale combat in a no frills kind of a way. Tactical decisions and number crunching are largely replaced by abstract terms and mechanics in BCR. GMs of any ttrpg can use this ruleset to handle faction conflicts in or out of session. BCR can also be used for solo play, GM vs PC battlefields, or as a standalone game.
Sci-fi marines duking it out with a swarm of bugs. A massive battlefield filled with armies of orks, dwarves, elves, and humans. Dueling samurai, mages … or gunslingers! These are all scenarios BCR can handle.