After Duke Xiao's death, King Huiwen became the new ruler of Qin and he put Shang Yang to death by chariot-tearing on charges of treason, but some believed that the king harboured a personal grudge against Shang because he was harshly punished for a minor infraction in his adolescence under Shang's reformed system. However, King Huiwen and his successors retained the reformed systems and they helped to lay the foundation for Qin's eventual unification of China under the Qin Dynasty in 221 BC. Shang Yang's theories were further elaborated later by Han Fei, another Legalist scholar who combined Shang's ideas with those of Shen Buhai and Shen Dao, that would form the core of the philosophies of Legalism. Qin rose to prominence in the late 3rd century BC after the reforms and emerged as one of the dominant superpowers of the Seven Warring States.