Qin reformed its political system in the year 356 B.C. It is known as Shangyang’s Reform. It enacted a new collection of decrees and encouraged the masses to grow plants and join the army. Owning vast fertile lands in present the central Shanxi plain and Sichuan Province, Qin soon surpassed other states in military power. But north nomads Donghu and Loufan frequently crossed the desert and harassed the north part of Qin. To resist their raids, Qin built a wall along its north border. This wall started from Mingxian County of Gansu Province, went northeast to present Longde and Kuyuan County of Ningxia Hui Autonomous Region, headed north along the Liupanshan Mountain, went on east to Huanxian County of Gansu Province and finally arrived at the bank of the Yellow River of Suide County of Shannxi Province.