The Qin dynasty, led by Qin Shi Huang, was the first to unify China into a single state in 221 BCE. Qin Shi Huang standardized weights, measures, and Chinese characters. He also had the Great Wall extended and linked to defend against invaders. To protect his legacy after death, Qin Shi Huang built the Terracotta Army of thousands of life-sized ceramic soldiers and other figures buried near his tomb.