You can read the original post for the full effect, but – wow.
Suffice to say it works like this.
Big Empire allows some foreigners inside its borders, not because it loves them, but because it thinks they will be useful cannon fodder and labor. Sacrifices get made, and the sick and weak die, so the foreigners get kind of angry.
Then, then they are inside the borders, the Big Empire mistreats the foreigners and breaks promises. That makes the foreigners even more angry, but now they’re inside the borders.
Finally, the foreigners beat the Big Empire’s armies and the Big Empire negotiates a peace with a foreign power inside its borders.