Qin (; Old Chinese: *; Wade-Giles: Ch'in) was an ancient Chinese state during the Zhou dynasty. It took its origin in a reconquest of western lands previously lost to the Rong; its position at the western edge of Chinese civilization permitted expansion and development that was unavailable to its rivals in the North China Plain. Following extensive Legalistic reform in the 3rd century , Qin emerged as one of the dominant powers of the Seven Warring States and unified China in 221  under Shi Huangdi. The empire it established was short-lived but greatly influential on later Chinese history.