From Wikipedia

Secrets Of China's First Emperor

The Qin Dynasty was the ruling Chinese dynasty between 221 and 206 BC. The Qin state was so named because its rulers were descendants of the first emperor's ancestors whose fief was called "Qin". The Qin's strength had been consolidated by Lord Shang Yang during the Warring States Period, in the 4th century BC. In the early third century BC, the Qin accomplished a series of swift conquests; the state subjugated the Chu, remnants of the Zhou Dynasty, and various other states to gain undisputed control of China.