This is exactly how things would go, which is why in human history warlords have never been a thing, and violent, oppressive men have never built empires.
and produce the court-based system we see today, with enforcement of the stick centralized to an authority that everyone agreed to (implicitly).
https://www.thesouthafrican.com/news/africas-top-10-dictator...
You need commanders for war.
Weaker humans usually sit through decimation until the guards come for them. Then they squeal for help. It is also rational. Consider that if you stand agaisnt the stronger enemy, the enemy might come back later with reinforcements and kill you.
Edit: I remembered what the Bible says happened to jews. The egyptians killed the jew children to keep the population in check, before exodus. And shortly after Jesus was born, Herod probably did the same.
If this is possible, then it is equally possible to just hit anyone you please with stick so that they are forced to do what you want.
Which means, the most violent eager person gets to rule. Which is what people who prefer court system don't want.