The Qin Dynasty lasted from 221 BC to 206 BC and was founded by Qin Shi Huang, who became the first emperor of a unified China. He believed in the philosophy of Legalism and used harsh methods, such as punishing or killing opponents, to strengthen his control over China. Some of the Qin Dynasty's major accomplishments included starting construction of the Great Wall, unifying China under a centralized government, and standardizing currency, script, weights and measures. However, Qin Shi Huang's oppressive policies led to an uprising after his death that overthrew the Qin Dynasty after just 15 years in power.