The State of Qin destroyed the Zhou Dynasty in 256 BC and finally destroyed the Six Kingdoms in 221 BC, establishing China's first feudal imperial state, the Qin Dynasty, and at the end of the Warring States Period, China achieved its first comprehensive unification.
The State of Qin was able to establish a state during the eastward migration of King Ping and was sealed in the Guanzhong region, the former capital of the Zhou Dynasty. During the period of Duke Mu of Qin, he appointed Baili Xi, Uncle Jian and other sages to rule the country, and the State of Qin was able to rise and strive to develop eastward, but both times the east was defeated by Duke Wen of Jin, the qin army was completely destroyed, and the strategy of going east was completely locked up by the State of Jin, so he had no choice but to turn to the west, fight with foreign tribes such as Xi Rong, and expand the land for thousands of miles, and was crowned by King Xiang of Zhou as an uncle, becoming a prince who dominated the west, and also laid the foundation for the final unification of the Qin state.
At the beginning of the Warring States era, the State of Qin had already undergone the turbulent rule of several generations of monarchs such as the Duke of Qin, and had long since declined into a marginal state, and one of the successors of the original State of Jin, the State of Wei, still suppressed the State of Qin and seized the land of Hexi of the State of Qin.
After The Death of Duke Xian, Duke Xiao of Qin succeeded to the throne. Duke Xiao was eager to reverse the decline, so he tried to attract talents, and shang martingale, a defender, entered the Qin state at this time. Under the persuasion of Shang Martin, Qin Xiaogong decided to change the law, and engaged in fierce debate with the conservative faction, and finally issued the "Order of Reclamation of Grass" in 359 BC, which opened the prelude to a comprehensive change of law.
In 356 BC, Duke Xiao appointed Shang Martin as the chief of zuo shu and implemented a comprehensive change of law, which involved economic, civil, military, state system, law and other aspects. In civil terms, we will reform the original customary household registration system, encourage the small family system of living separately from households, encourage farming and weaving, and emphasize agriculture and business. Militarily, military law was promulgated, the system of shiqing shilu, which had been passed down from generation to generation, was implemented, and the knighthood was rewarded with merit. In terms of law, the Qin Law was formulated, the law of sitting together was implemented, private fighting was severely punished, and so on. Later, Qin Xiaogong also worshiped Shang Martingale to create a second transformation of the law, and carried out a more in-depth and thorough transformation of the law. After the change of law, the Qin state quickly became stronger. Qin Xiaogong also decided to actively intervene in the affairs of the Central Plains and develop eastward, first attacking the State of Wei and recovering the land of Hexi, and then taking advantage of the fact that the main force of the State of Wei was completely annihilated by the State of Qi, attacking the State of Wei, gaining a large area of territory of the State of Wei and opening a window out of the east.
After the death of Duke Xiao of Qin, King Huiwen of Qin succeeded to the throne, and after he succeeded to the throne, he killed Shang Martingale, but retained the fruits of the Shang Martingale Transformation Law. During the reign of King Huiwen of Qin, the curtain was opened on the eastward departure of the Qin state. He appointed Gongsun Yan, Sima Cuo, Zhang Yi, and others to conquer Yiqu to the north, stabilize the rear, attack Bashu to the west, expand the territory of the State of Qin, and mediate with the State of Chu in various means of military diplomacy to the south, stabilize the south, and continue to attack the State of Wei to the east. The State of Wei was in decline, and the State of Qin was already a large country second to none at this time.
After the death of King Huiwen of Qin, his son Yingdang succeeded to the throne, but ruled for a short time, and was succeeded by his brother Yingji after his death, who was the King of Qin Zhaoxiang. King Zhaoxiang of Qin reigned for more than fifty years, and under his leadership the State of Qin became the most powerful state in the Warring States. At the beginning of the succession of King Zhaoxiang of Qin, the State of Qi in the Warring States was a great power comparable to the strength of the State of Qin, and the State of Zhao, one of the Three Jin Dynasties, also became a state with strong military strength through the reform of Hufu Riding and Shooting, and even the successful succession of King Zhaoxiang of Qin had the influence of King Wuling of Zhao, and these two countries became the main opponents of the unification of the Qin State.
In the nineteenth year of King Zhaoxiang of Qin, he sent emissaries into Qi to meet the King of Qi, honoring the monarchs of Qin and Qi as emperors, Qin Jun as the Western Emperor, and King Tang as the Eastern Emperor, but the King of Qi followed Su Qin's suggestion to cancel the title and asked the princely states to jointly attack the Qin state, and the Qin state was forced to cancel the imperial title. The strength of the State of Qi was a great threat to the unification of the State of Qin, but the State of Qi was playing itself to death. When King Tang's father, King Xuan of Qi, took advantage of the internal turmoil in Yan to attack the State of Yan first, almost destroying the country, and later withdrew under the influence of Qin Zhao and other states, but also planted the seeds of revenge for the State of Yan. After succeeding to the throne, King Xiang went on a campaign everywhere, defeated the State of Chu at Chongqiu, defeated the State of Wei and the State of Zhao at Guanjin, and joined forces with Han Zhao Wei to attack the State of Qin, forcing the State of Qin to return the land occupied by the East, and also helped the State of Zhao to destroy the State of Zhongshan, and to unite with the State of Chu and the State of Wei to annex the State of Song, after canceling the imperial title, it was an opportunity to reconcile with the princely states, but the King of Qi was too arrogant, and the strength of the State of Qi was too strong and did not agree with the states, and because of the years of conquest, the people could not stand it, and finally lost the opportunity to consolidate their rule.
In the end, the State of Yan, which had almost destroyed the country, saw that the State of Qi had lost peace with the various countries outside, and the people's hearts and minds were in turmoil at home, and felt that the time was ripe, so it united with the five kingdoms of Zhao, Wei, Han, and Chu to fight Qi. The State of Qi was greatly defeated, and Le Yi led the Yan army to destroy Qi in one fell swoop, capturing more than seventy cities in the State of Qi, leaving only Tian He and the fortified Jucheng and other two cities. Although Tian He later revived the State of Qi by using the psychology of the new King of Yan to suspect Leyi, the strength of the State of Qi was much worse than before, and the State of Qin had lost a powerful opponent.
After the decline of the State of Qi, the State of Zhao became the only opponent for the unification of the State of Qin, but the State of Zhao had a congenital defect, its land population was insufficient, and although it was militarily strong, its economic strength was too weak compared with the State of Qin. In 262 BC, the State of Qin attacked Korea and cut off the connection between the north and south of Korea, Korea was divided into two, the northern Shangdang region became an enclave, and there was a risk of being annexed by the State of Qin, Shangdang Taishou was too reluctant to surrender to Qin, so he surrendered to the State of Zhao, wanting to borrow the State of Zhao to confront the State of Qin, so the great war between the State of Zhao and the State of Qin began. The State of Qin was very angry at the Interception of the State of Zhao and sent a large army to attack the Shangdang region, and Qin zhao's hundreds of thousands of troops were opposed in Changping, but because the overall comprehensive national strength of the State of Zhao was not as good as that of the State of Qin, and could not withstand a long war of attrition, the Monarch of the State of Zhao replaced Lian Po, who insisted on defending the battle, and replaced it with a young general Who advocated a decisive battle, Zhao Kuo, but this was also in the hands of the Qin army, and the Qin army secretly replaced it with the best military commander Bai Qi, cutting off the Zhao army's grain route and retreat. Surrounded by the main force of the Zhao army, Zhao Kuo was killed in the breakthrough, and the entire 400,000 troops of the Zhao army were destroyed, known in history as the Battle of Changping. Since then, none of the six countries has the ability to confront the Qin state.
However, the Qin army also suffered heavy losses in the great war, and did not take the opportunity to expand the victory to eliminate the Zhao state, giving the Zhao state a chance to breathe, and the Wei state Xin Lingjun stole the charm to save Zhao and lifted the siege of Handan, and after a period of time, China entered a period of relative stability.