Being Demoted To The Frontier, He Became The Strongest Vassal King

At the beginning of the journey, I encountered Immortal Jump and was demoted to the frontier to eat dirt.
The emperor wants to trap me in a border town? The courtiers want to see my joke?
But I don’t know that I have modern knowledge, clearing wasteland, refining steel, and training cavalry!
Three years later, the cavalry trampled the grassland, and even the princesses of the enemy countries knelt down and begged for marriage...
The man on the dragon throne regretted:
The one he exiled with his own hands was not an abandoned son, but the real Qianlong of Great Zhou!
"Your Majesty, these thousands of miles of frontier...now belong to me!"
It turns out that exile was the beginning of his dominance!