Meng Tian (c. 250 BC – 210 BC) was a Chinese inventor and military general of the Qin dynasty who distinguished himself in campaigns against the Xiongnu and in the construction of the Great Wall of China. He was the elder brother of Meng Yi. He descended from a great line of military generals and architects. His grandfather, , was a general from the era of King Zhao; and his father, Meng Wu, was also a general who served as a deputy to Wang Jian. Life In 224 BC, having recently conquered Wei, the Qin king Ying Zheng appointed Li Xin as commander-in-chief and Meng Tian as his vice-general to lead a 200,000 strong army in an assault against Chu. The invasion was successful at first, Meng Tian's army took Qigui but then, both Li Xin and Meng Tiang armies were effectively annihilated by Chu troops under Xiang Yan and Lord Changping. Following this defeat, Ying Zheng appointed Qin generals Wang Jian and Meng Wu as commanders of a 600,000 Qin army in order to finally achieve the conquest of Chu. By the time the Qin state conquered the other six states and began its reign over a unified China in 221 BC, the nomadic Xiongnu had grown into a powerful invading force in the north and started expanding both east and west. Qin Shi Huang, the first emperor of the Qin dynasty, sent a 300,000-strong army headed by Meng Tian to drive the Xiongnu northward for 1,000 li (about 416 km) and began work on what has become known as the Great Wall to guard against invasion. The defensive works he began were said to extend over 10,000 li (4,158 km) "from Lintao to Liaodong and even extended across the Yellow River and through Yangshan and Beijia.", that is, from the southwest corner of the Ordos Loop to the Yellow Sea. Yangshan and Beijia are hard to locate, but the wall ran along the Yellow River and included all of the Ordos Loop. Meng Tian's ingenuity can be seen in the efficient (though inhumane) building policy, the consideration of topography, and the utilisation of natural barriers. Meng Tian supervised the construction of a road system linking the former Yan, Qi, Wu and Chu areas, as well as a number of roads especially for imperial use. The system eventually formed played an extremely important role in ancient transportation and economic