First Emperor of China - Early Conquests

How was Ying Zheng, China's first emperor, able to unify seven warring states which highly valued independence? Why were prisoners of war, at the time, buried alive?

To learn more about Ying Zheng's early years, before he became the First Emperor, watch this clip from Secrets of China's First Emperor: Tyrant and Visionary (by Koch Vision). The film is based on The Records of the Grand Historian and includes archival references and recreated scenes.