The Conquer of Qin and Shihuangdi
When the ruler of Qin died, Shang Yang was left without protection at court. Jealous and power hungry persons within the court had Shang Yang executed, but the wealth and power of the principality of Qin lived on. And Qin started winning large battles. During this era of "Warring States," chariots had been replaced by cavalry and armies were mainly infantry conscripts armed with iron swords, crossbows and metal tipped spears.
In 314 BCE -- twenty-four years after the death of Shang Yang -- Qin won a military victory over nomads to its north. In 311, Qin expanded southward against more nomadic people, and there it founded the city of Chengdu. By now, other states had expanded: Yan against so-called barbarians east of the Liao River, and Chu south of the Yangzi River. War and conquest had reduced the number of states to eleven. Qin joined a coalition of four other states against Qi, which the allies of Qin feared the most. Qi was traditionally expansionist and hegemonic, well organized, densely populated relative to most other states, high in food production and had grown wealthy also from trade in iron and other metals. To their detriment, the allies of Qin viewed Qin as semi-barbaric and therefore weaker and less of a threat than Qi.
In 256, Qi absorbed Lu, and Qin expanded into territory that belonged to the Zhou family -- an area around Luoyang containing about 30,000 people and thirty-six villages. A Zhou prince counter-attacked, trying to claim the Zhou throne for himself. Qin's army defeated him, and the Zhou came to an end.
In 246 BCE, Yong Zheng, the thirteen-year-old son of the ruler of Qin, succeeded his father. After sixteen years of rule, Zheng embarked upon the conquest of the remaining states that had been a part of Zhou civilization. Armies of hundreds of thousands were involved on both sides. Qin defeated one state after another: Han in the year 230, Zhao in 228, Wei in 225, the large but more sparsely populated and less tightly knit Chu in 223, Yan in 222 and the powerful state of Qi in 221. Occasionally, to eliminate possible military opposition, Qin's armies slaughtered all enemy males of military age.
What is called the Period of Warring States was over. Zheng became ruler of all that had been Zhou civilization. He went to a sacred mountain, Dai Shan, where, it would be said, he received the mandate from heaven to rule the entire world. He took the name Shihuang-di (di signifying emperor), and Qin Shi Huang, and he expanded the frontiers of what had been Zhou civilization -- southward to Guangzhou and to Guangxi, creating what would thereafter be considered China. And he pushed into Annam, or northern Vietnam -- an area the Chinese would hold only temporarily. Shihuangdi had become the First Emperor and great father of China.