In 221 B.C., the Qin general Wang Ben attacked the Qi State from the south of Yandi, captured the Qi King Tian Jian, and the Qi State was declared extinct, since then the grand cause of Qin Shi Huang to destroy the Six Kingdoms has been a complete success, and the chaotic situation of more than 500 years of secession on the Central Plains has come to an end, and Qin Shi Huang has established China's first unified feudal state.
After Qin destroyed the Six Kingdoms, the empire's Chinese territory stretched from Ningxia in the north, to the south bank of the Yangtze River in the south, to the East China Sea and the Yellow Sea in the east, and to Bashu in the west. However, the unification of the Central Plains did not mean that the four seas were peaceful, and the newly born Qin Empire was still facing the threat of two powerful enemies, namely the Xiongnu in the north and the Baiyue in the south.
The Xiongnu have always been one of the most powerful nomadic peoples in northern China, with strong folk customs and strong combat effectiveness, and have long been active between the Yin Mountains in the south and Lake Baikal in the north. When Qin Shi Huang unified the six countries, the Xiongnu had entered the slave society, occupying the vast areas around today's Inner Mongolia, Ningxia and present-day Mongolia.
After Qin unified the six kingdoms, Qin Shi Huang was the world, and within the four seas, the Xiongnu posed the greatest threat to Qin. In order to make the foundation of the Qin Empire everlasting, Qin Shi Huang decided to take the initiative and strike first, so the war between the Qin Empire and the Xiongnu inevitably happened.
In order to conquer the Xiongnu, Qin Shi Huang in the year of the unification of the six countries, that is, in 221 BC, ordered the construction of the Chi Road leading to Beidi (now the northwest of Ningxian County, Gansu) and Longxi (now Lintao, Gansu).
After years of pre-war preparations, in 215 BC, Qin Shi Huang sent the famous general Meng Tian to lead about 300,000 elite Qin troops to the north to fight against the Xiongnu. The strategic objective of this military campaign was to recover the Xiongnu-occupied "Henan Land" (i.e., the Hetao region of present-day south-central Inner Mongolia and northern Shaanxi) and to establish a solid border defense system.
Meng Tian's army marched from Shangjun (roughly in present-day northern Shaanxi Province) of the Qin Dynasty and advanced along the route of the time to the Yulin region, and then entered the Hetao region.
In order to consolidate the results of the war and prevent the Huns from coming back, in 214 BC, Meng Tian led the main force to cross the river and enter the highlands of Yinshan and Helan Mountain, and found the main force of the Xiongnu in Gaoque, Yangshan, Beijiao and other places, and launched a fierce battle with it, giving the Xiongnu a huge blow. After this battle, the Xiongnu head Mandan Yu was forced to withdraw from the highlands of Yinshan and Helan Mountain, continued to retreat north for more than 700 li, and retreated to the nomadic area of Monan north of Yinshan.
So far, the Qin attack on the Xiongnu was a complete success, not only successfully recovering the "Henan land", making the Hetao area permanently return to the Chinese territory, but also forcing the Xiongnu to retreat more than 700 miles north. Subsequently, in order to consolidate the border defense, Qin Shi Huang ordered Meng Tian to lead the army to be stationed in the north and implement the tuntian policy, which not only ensured the military rations, but also promoted the development and stability of the border areas. Jiuyuan County was set up here, 34 counties were placed under it, and more than 30,000 households moved from the interior to develop the Henan region, making the area a first-line base against the Xiongnu.
In 213 B.C., after the victory of the battle of the Xiongnu in the north, Qin Shi Huang took precautions and ordered to connect the original Great Wall of Qin, Zhao and Yan, which is known as one of the world cultural heritages, starting from Lintao in Gansu Province in the west and reaching the Great Wall of Jieshi in Liaodong in the east. Later generations have a lot of negative comments on Qin Shi Huang's construction of the Great Wall, here it is necessary to clarify for Qin Shi Huang, Qin Shi Huang's construction of the Great Wall is a military defense project, its fundamental purpose is to protect the development of agricultural civilization in the Central Plains, but also to reduce the burden of the people, because the Xiongnu are nomadic people, nomads are not like agricultural civilization, will not settle for a long time, but with the irregular migration of water and grass, there is no fixed place, so its range of activities is very large, and it can not be killed if it wins, and it cannot be eradicated from the root. Without the protection of the Great Wall, it is necessary to set up a very long defense line and a large army to defend, which will lead to the ** regime constantly launching wars to attack the Xiongnu, which is very consuming of national strength and will increase a great burden on the domestic people in the long run.
On the other hand, the construction of the Great Wall was not founded by Qin Shi Huang, since the Western Zhou Dynasty, the Central Plains countries such as Qin, Zhao, and Yan that directly bordered the Xiongnu have begun to build the Great Wall, and by the time of Qin Shi Huang, the original Great Wall was only connected. Later generations have ** opinions on Qin Shi Huang's construction of the Great Wall, mainly based on the fact that at the beginning of the Qin state, many years of war, all kinds of waste to be rebuilt, and urgently need to recuperate with the people, and Qin Shi Huang in order to consolidate his rule and realize the ideal of long-term peace and stability, with his personal will to forcefully mobilize the state machinery to operate at a high load, making the people work hard and complain. Therefore, Qin Shi Huang blamed all the suffering caused by the construction of the Great Wall, and Qin Shi Huang expressed a bit of grievance.
The existence of the Great Wall ensured the consolidation of border defense and the security of the country, and provided a stable environment for agricultural production in the Central Plains. There is a saying in the Qin theory: "But the Xiongnu are more than 700 miles, the Hu people dare not go south and graze horses, and the soldiers dare not bend their bows and complain." This is a positive affirmation of Qin Shi Huang and the Great Wall.
The battle of the Qin Dynasty against the Xiongnu enabled the Qin Dynasty to achieve long-term peace and stability on the northern border, just as the great man famously asserted in the early days of the War to Resist US Aggression and Aid Korea: "A hundred punches are opened, lest a hundred punches come". Qin Shi Huang's war against the Xiongnu had a profound impact on the pattern of ethnic relations in northern China, and also provided experience and foundation for the later Central Plains dynasty in China to deal with the relations with the northern nomads.