Why do wars exist
Why don't you just count how many soldiers you have and how many they have and see who has the better equipment and whoever has the worst equipment and soldiers surrenders

>>212450757 (OP)
Lets say your tribe has 50 people armed with spears and the rival tribes have a hundred people without any weapons, you can easily defend yourself if they attack right now, but if they start crafting spears of their own then they can easily massacre your tribe, so it only make sense to conquer them now.

because killing people is fun