Definition: The Qin Dynasty [221-206 BC], while only fifteen years in duration and only including three emperors, was one of the most important and influential of periods in Chinese history. The first emperor Qin (Qin Shi Huangdi) united the "Warring Tribes," creating the rudimentary elements of a united China. Other achievements of the Qin dynasty include strengthening the Great Wall, and standardizing currency and language. The army of terra cotta soldiers also dates to the Qin dynasty; they were found in the emperor Qin Shi Huangdi's tomb. The harshness of the Qin regime led to its downfall the year after Shihuangdi's death.