Uncivilized Humanoid setting?

Most of the time I think of something, I discover later on that I'm just remembering something that I've read somewhere before and half-forgotten. So......

Goblinoid tribes, orc tribes, gnoll tribes, human barbarian tribes, and whatever else lives out beyond civilization. A charismatic leader (the PCs) could conquer or otherwise unite these tribes, becoming a great leader which presumably would then move on to invade civilized lands. Kind of like the backstory to "red hand of doom", but from the perspective of the bad guys. One rival tribe befriended, conquered, or otherwise neutralized at a time, by whatever means necessary, like the rise of Genghis Khan.

Is there a rpg game or supplement out there that has this for a base assumption?

I've definitely ran a game like this where the PCs were all goblins, trying to build up their tribe and alliances with other "greenskin" races while repelling "civilized humanoids" (mostly adventurers but later knights from the nearby township) who sought to "clear them out".

IIRC there was a "Green Races" supplement for either 2E or 3.X D&D at one point.