According to Sima Qian, Modu was a gifted child but his father Touman wanted the son of another of his wives to succeed him. To eliminate Modu as a competitor to his chosen heir, Touman sent the young Modu to the Yuezhi as a hostage; then he attacked the Yuezhi in the hopes that they would kill Modu as retribution. Modu was able to escape this fate by stealing a fast horse and returned to the Xiongnu, who welcomed him as a hero. As reward for this show of bravery, his father appointed him the commander of 10,000 horsemen.