In the 30th year of Emperor Yuan's reign, he deposed Prince Hong and established Prince Yu. He issued an edict to make Jiuxiao, the lord of Mu City, the Taifu. Jiuxiao was thirteen years old and Prince Yushang was ten years old.
In the thirty-fifth year of Emperor Yuan's reign, Ji Yao invaded from the north. In more than three months, they occupied the four cities of Tuzhou, Mo, Yan, and Gao. The imperial capital was greatly frightened, and the people were all panicked. Not long ago, the emperor appointed Prince Yu as the general of Fuyuan and the superintendent of the army, and went north to resist foreign enemies. The whole country was in an uproar.