Three Kingdoms

The Three Kingdoms () from 220 to 280 AD was the tripartite division of China among the dynastic states of Cao Wei, Shu Han, and Eastern Wu. The Three Kingdoms period was preceded by the Eastern Han dynasty and was followed by the Western Jin dynasty. The short-lived state of Yan on the Liaodong Peninsula, which lasted from 237 to 238, is sometimes considered as a "4th kingdom". Academically, the period of the Three Kingdoms refers to the period between the establishment of Cao Wei in 220 and the conquest of the Eastern Wu by the Western Jin in 280. The earlier, "unofficial" part of the period, from 184 to 220, was marked by chaotic infighting between warlords in various parts of China during the downfall of the Eastern Han dynasty. The middle part of the period, from 220 to 263, was marked by a more militarily stable arrangement between three rival states of Cao Wei, Shu Han, and Eastern Wu. The later part of the era was marked by the conquest of Shu by Wei in 263, the usurpation of Cao Wei by the Western Jin in 266, and the conquest of Eastern Wu by the Western Jin in 280. The Three Kingdoms period is one of the bloodiest in Chinese history. A nationwide census taken in 280 AD, following the reunification of the Three Kingdoms under the Jin shows a total of 2,459,840 households and 16,163,863 individuals which was only a fraction of the 10,677,960 households, and 56,486,856 individuals reported during the Han era. While the census may not have been particularly accurate due to a multitude of factors of the times, in 280, the Jin did make an attempt to account for all individuals where they could. Technology advanced significantly during this period. Shu chancellor Zhuge Liang invented the wooden ox, suggested to be an early form of the wheelbarrow, and improved on the repeating crossbow. Wei mechanical engineer Ma Jun is considered by many to be the equal of his predecessor Zhang Heng.