Genghis Kahn, my favorite barbarian.
The man knew how to conquer.
At the first walled city destroy it all. Keep a handful of survivors and let them watch you kill every living thing down to the last cat, dog and bird.
Turn the handful loose and let them run to the nearest city.
When your army arrives at that city offer terms of surrender: Open your gates and give me all your valuables or be destroyed.
When they open the gates slaughter the ruling class, take their treasure and install your own people.
Round up survivors of the first city, pay them and send them to neighboring cities with the news: Surrender and the citizens live, fight and everyone dies.
Amazing how badly people want to live.
If something is useful to your people, keep it.
If it isn’t useful, destroy it. It saves headaches later on.
Make sure the laws are few, easily understood and ruthlessly administered.
I don’t have to agree with everything he did to understand the beautiful simplicity behind his actions.