The Warring States Period followed the Spring and Autumn Period. The traditional date for the beginning of the Warring States Period was the partition of the State of Jin into Han, Zhao, and Wei.
However, the Warring States Period was, in general, a period when regional warlords annexed smaller states around them and consolidated their rule. The period began with China divided in many little kingdoms; eventually seven states, known as the "Seven Great Powers" (戰國七雄/战国七雄 Zhànguó Qīxióng), rose to prominence: Qi, Chu, Yan, Han, Zhao, Wei and Qin. Another sign of this shift in power was a change in title: in the Spring and Autumn Period, warlords still considered themselves dukes (公 pinyin: gōng) of the Zhou Dynasty king; but now the warlords began to call themselves kings (王 pinyin: wáng), meaning they were equal to the Zhou king.
The Warring States Period saw the proliferation of iron working in China, replacing bronze as the dominant metal used in warfare. Areas such as Shu (modern Sichuan) and Yue (modern Zhejiang) were also brought into the Chinese cultural sphere during this time. Walls built by the states to keep out northern nomadic tribes and each other were the precursors of the Great Wall of China. Different philosophies developed into the Hundred Schools of Thought, including Confucianism (elaborated by Mencius), Taoism (elaborated by Zhuang Zi), Legalism (formulated by Han Feizi) and Mohism (formulated by Mo Zi). Trade also became important, and some merchants had considerable power in politics. In order to deal with these changes, Shang Yang, a minister of the State of Qin, initiated a series of reforms that are regarded to have given the Qin its edge over the other six states.
Near the end of the Warring States Period, the State of Qin, based in modern Shaanxi province, became disproportionately powerful compared to the other six states. Policy of the six states then became overwhelmingly oriented towards dealing with the Qin threat, with two opposing schools of thought: Hezong (合縱/合纵 pinyin: hézòng), or alliance with each other to repel Qin expansionism; and Lianheng (連橫/连横 pinyin: liánhéng), or alliance with Qin to participate in its ascendancy. There were some initial successes in Hezong, though it eventually broke down. Qin then exploited the Lianheng strategy to defeat the states one by one. Eventually Qin conquered all and ushered in the Qin Dynasty in 221 BC.
