Excerpts from Books and Wikipedia
"To the shock of both kings, the smaller Jin force triumphed. With that defeat, Fu Jian’s bid to reunify China was over. . . . Once defeated, Fu Jian began to lose territories to rebellion and revolt, one at a time. Two years after his loss at the Fei river, Fu Jian was strangled by one of his own subordinates.13 The strangler was named Tuoba Gui. Like Fu Jian himself, he was of northern stock; his ancestors were nomads of the Xianbei tribe, and the Tuoba family name testified to his “barbarian” origins. His own native state, the Dai state, had been conquered by Fu Jian ten years earlier; his grandfather had been its prince until Fu Jian annexed the state as part of his growing northern empire. Now Tuoba Gui declared Dai’s independence. He changed its name from the Xianbei “Dai” to the Chinese “Bei Wei,”* and he changed his own family name from the Xianbei “Tuoba” to the Chinese “Yuan.” With his Chinese identity firmly in place, he then began his own campaign to conquer and unify the north." [Bauer: Medieval World, p. 18-9]