After years of annexation among the vassal states, only seven states,
plus a few smaller ones, were left during the Warring States Period.
The Seven Powers of the Warring States Period, namely the Qi, Chu, Yan,
Han, Zhao, Wei and Qin, gradually conquered the smaller powers.
The Warring States Period can be divided into three stages. The first
stage began in 475BC and ended in 338BC, when the king of the Zhou, the
last king of the Shang Dynasty, was killed. During this period, many
statesmen were eager to strengthen their states through reform, such as
Li Kui in the Wei, Wu Qi in the Chu and later Shang Yang in the Qin.
This was a comparatively stable period.
Agriculture, industry and economy developed during the Warring States
Period. The increasing popularity of iron tools marked a revolutionary
innovation of production tools and the development of social productive
forces.
The second stage began from 338BC and ended in 288BC. During this
period fierce fighting persisted among the seven powers as each tried
to annex its neighbor. In 288BC, the Qi and Qin became the Western
Empire and Eastern Empire. The wars escalated. In 284BC, six states
were united and launched a war against the Qi.
The third stage was from 284 to 221BC. In 221BC, the Qin unified the
country after conquering its six rival states, ending the turbulent
Warring States Period.