<P> The Imperial China Period can be divided into three subperiods: Early, Middle, and Late . </P> <P> Major events in the Early subperiod include the Qin unification of China and their replacement by the Han, the First Split followed by the Jin unification, and the loss of north China . The Middle subperiod was marked by the Sui unification and their supplementation by the Tang, the Second Split, and the Song unification . The Late subperiod included the Yuan, Ming, and Qing dynasties . </P> <P> Historians often refer to the period from Qin dynasty to the end of Qing dynasty as Imperial China . Though the unified reign of the First Qin Emperor lasted only 12 years, he managed to subdue great parts of what constitutes the core of the Han Chinese homeland and to unite them under a tightly centralized Legalist government seated at Xianyang (close to modern Xi'an). The doctrine of Legalism that guided the Qin emphasized strict adherence to a legal code and the absolute power of the emperor . This philosophy, while effective for expanding the empire in a military fashion, proved unworkable for governing it in peacetime . The Qin Emperor presided over the brutal silencing of political opposition, including the event known as the burning of books and burying of scholars . This would be the impetus behind the later Han synthesis incorporating the more moderate schools of political governance . </P> <P> Major contributions of the Qin include the concept of a centralized government, and the unification and development of the legal code, the written language, measurement, and currency of China after the tribulations of the Spring and Autumn and Warring States periods . Even something as basic as the length of axles for carts--which need to match ruts in the roads--had to be made uniform to ensure a viable trading system throughout the empire . Also as part of its centralization, the Qin connected the northern border walls of the states it defeated, making the first Great Wall of China . </P>

Who founded the first real centralized empire in china