Qin's wars of unification

Qin's wars of unification were a series of military campaigns launched in the late 3rd century BC by the state of Qin against the other six powers remaining in China — Han, Zhao, Yan, Wei, Chu and Qi. Between 247 and 221 BC, Qin had developed into one of the most powerful of China's Seven Warring States that coalesced in the wake of the Zhou dynasty's decline, by now retaining a weak and merely ceremonial position among the warring states. In 230 BC, King Ying Zheng of Qin began the sequence of campaigns that would bring the Warring States period to a close, setting out to conquer each remaining sovereign one by one. This was completed in 221 BC with the fall of Qi, leaving the former Zhou sphere unified under a more centralized Qin control. Ying Zheng declared himself the First Emperor, or Qin Shi Huang—becoming the first sovereign over a unified China under the imperial Qin dynasty.