How was the unification of china achieved?

China was unified by Qin Shi Huang in 220 BC then he defected all of the, what was known at the time, the Warring States.

According to sources, his rise to power was based on disregarding the rules of war at the time. At the time it was accepted that prisoners of war will be well treated as almost honoured guest. However this would had put a stain on his army and supplies. He got around this my simply executing all prisoners of war each time he won a battle. No prisoners no counter rebellions, no stain on his supplies and army.

 unification of China ca ~ 220 BC was thought about by bloodshed and being a tyrant.