During the Warring States period, Qin grew powerful under Shang Yang's legalist reforms, and militarily became increasingly more successful, and its rivals to the east claimed that the Qin army was a "troop of tigers and wolves", and it was often said that "Guanzhong produces generals; Guandong produces ministers". After constructing irrigation systems such as Zhengguo Canal, the already fertile Guanzhong region became extremely productive, allowing Qin state to become the preeminent power, repeatedly defeating and seizing more territory from its rivals to the east, and eventually unified China and established the Qin dynasty in 221 BC.