This is Modu Chanyu. He was the son and heir of the emperor. Specifically, the Xiongnu Empire’s emperor, who ruled the area of modern Mongolia plus some change. When he was younger, the emperor wanted another son to succeed him, so he sent Modu as hostage to the Yuezhi people. He then attacked the Yuezhi, hoping they would kill Modu as revenge for the emperor’s betrayal. The plan backfired. Modu escaped on a fast horse, returning a hero to the Xiongu and his father was forced to make him commander of 10,000 men to ‘honor’ his courage.
Modu Chanyu was smart. He knew the emperor still did not like him. So Modu slowly gathered an elite group of warriors, drawn by his reputation for bravery. To test their loyalty to him Modu ordered the warriors to kill his favorite horse. If they did not comply, he killed them. Then Modu ordered the warriors to kill his favorite wife. If they did not murder her, he killed them. So later when he ordered his warriors to kill the emperor, his father, they did not hesitate. Modu Chanyu became emperor, expanding the Xiongnu’s territory and forcing Han China to submit to him.