China is the world's oldest continuous major civilization, with written records dating back about 3,500 years and with 5,000 years being commonly used by Chinese as the age of their civilization. Successive dynasties developed systems of bureaucratic control, which gave the agrarian-based Chinese an advantage over neighbouring nomadic and mountain dwelling cultures. The development of a state ideology based on Confucianism (100 BC) and a common system of writing (200 BC) both strengthened Chinese civilization. Politically, China alternated between periods of political union and disunion, and was often conquered by external ethnicities, of which many were eventually assimilated into the Chinese identity. These cultural and political influences from many parts of Asia as well as successive waves of immigration and emigration merged to create the familiar image of Chinese culture and people today.
Since around 1000 BC China consisted of many small kingdoms. All of these were unified under one emperor in 221 BC by the Qin state, ushering in the Qin Dynasty.
Over the course of centuries, China underwent periods of unity and disunity, order and disorder.
In the 18th century, China achieved a decisive technological advantage over the peoples of Central Asia, while simultaneously falling behind Europe technologically. This set the stage for the 19th century, in which China adopted a defensive posture against European imperialism while simultaneously extending control into Central Asia.
In the early 20th century, the institution of the Emperor of China disappeared, and China entered a period of disunion started by the Chinese Civil War. There are now two nations which lay formal claim to the title of "China": the People's Republic of China (also called "Mainland China") and the pre-revolution government of the Republic of China which administers Taiwan and several small islands of Fujian.