Millions Of People Are Returning Home For The Weekend, China

The first unified Chinese state was established by Qin Shi Huang of the Qin state in 221 BC, who proclaimed himself as the "First Emperor" and created many reforms in the Empire, notably the forced standardization of the Chinese language and measurements. The Qin Dynasty lasted only fifteen years, as its harsh legalist and authoritarian policies soon led to widespread rebellion.
The subsequent Han Dynasty ruled China between 206 BC and 220 AD, and created a lasting Han cultural identity among its populace that extends to the present day. The Han Dynasty expanded the empire's territory considerably with military campaigns reaching Korea, Vietnam, Mongolia and Central Asia, and also helped establish the Silk Road in Central Asia.
After Han's collapse, another period of disunion followed, including the highly chivalric period of the Three Kingdoms. Independent Chinese states of this period such as Wu opened diplomatic relations with Japan, introducing the Chinese writing system there. In 580 AD, China was reunited under the Sui. However, the Sui Dynasty was short-lived after a failure in the Goguryeo-Sui Wars (598–614) weakened it.
Under the succeeding Tang and Song dynasties, Chinese technology and culture reached its zenith. The Tang Empire was at its height of power until the middle of the 8th century, when the An Shi Rebellion destroyed the prosperity of the empire. The Song dynasty was the first government in world history to issue paper money and the first Chinese polity to establish a permanent standing navy. Between the 10th and 11th centuries, the population of China doubled in size. This growth came about through expanded rice cultivation in central and southern China, and the production of abundant food surpluses.