Cao Wei in the context of "Weidu"

The Three Kingdoms of Cao Wei, Shu Han, and Eastern Wu dominated China from AD 220 to 280 following the end of the Han dynasty. This period was preceded by the Eastern Han dynasty and followed by the Western Jin dynasty. Academically, the periodisation begins with the establishment of Cao Wei in 220 and ends with the conquest of Wu by Jin in 280. The period immediately preceding the Three Kingdoms, from 184 to 220, was marked by chaotic infighting among warlords across China as Han authority collapsed. The period from 220 to 263 was marked by a comparatively stable arrangement between Cao Wei, Shu Han, and Eastern Wu. This stability broke down with the conquest of Shu by Wei in 263, followed by the usurpation of Cao Wei by Jin in 266 and ultimately the conquest of Wu by Jin in 280.

The Three Kingdoms period including the collapse of the Han was one of the most dangerous in Chinese history due to multiple plagues, widespread famines, and civil war. A nationwide census taken in 280, following the reunification of the Three Kingdoms under the Jin showed 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.

Han (漢; 221–263), known in historiography as Shu Han (蜀漢 [ʂù xân] ) or Ji Han (季漢 "Junior Han"), or often shortened to Shu (Chinese: 蜀; pinyin: Shǔ; Sichuanese Pinyin: Su < Middle Chinese: *źjowk < Eastern Han Chinese: *dźok), was a dynastic state of China and one of the three major states that competed for supremacy over China in the Three Kingdoms period. The state was based in the area around present-day Hanzhong, Sichuan, Chongqing, Yunnan, Guizhou, and north Guangxi, an area historically referred to as "Shu" based on the name of the past ancient kingdom of Shu, which also occupied this approximate geographical area. Its core territory also coincided with Liu Bang's Kingdom of Han, the precursor of the Han dynasty.

Shu Han's founder, Liu Bei (Emperor Zhaolie), had named his dynasty "Han", as he considered it a rump state of the Han dynasty and thus the legitimate successor to the Han throne, while the prefix "Shu" was first used by the rival state of Cao Wei to delegitimize the claims of the Shu Han state to orthodox succession. Later on when writing the Records of the Three Kingdoms, the historian, Chen Shou, also used the prefix "Shu" to describe Liu Bei's state of Han as a historiographical prefix to differentiate it from the many other states officially named "Han" throughout Chinese history.

Wu (Chinese: 吳; pinyin: Wú; Middle Chinese *ŋuo < Eastern Han Chinese: *ŋuɑ), known in historiography as Eastern Wu or Sun Wu, was a dynastic state of China and one of the three major states that competed for supremacy over China during the Three Kingdoms period. It previously existed from 220 to 222 as a vassal kingdom nominally under its rival state Cao Wei but declared complete independence in November 222. It was elevated to an empire in May 229 after its founding ruler Sun Quan (Emperor Da) declared himself emperor.

The name Wu was derived from the place it was based in—the Jiangnan (Yangtze River Delta) region, which was also historically known as Wu. It was called Dong Wu ("Eastern Wu") or Sun Wu by historians to distinguish it from other Chinese historical states with similar names in that region, such as the Wu state of the Spring and Autumn period and the Wuyue kingdom of the Five Dynasties and Ten Kingdoms period. It was called Eastern Wu because it occupied most of eastern China in the Three Kingdoms period, and Sun Wu because the family name of its rulers was Sun.

The end of the (Eastern) Han dynasty was the period of Chinese history from 189 to 220 CE, roughly coinciding with the tumultuous reign of the Han dynasty's last ruler, Emperor Xian. It was followed by the Three Kingdoms era (220–280 CE). During the end of the Han dynasty, the country was thrown into turmoil by the Yellow Turban Rebellion (184–205). Meanwhile, the Han Empire's institutions were destroyed by the warlord Dong Zhuo and fractured into regional regimes ruled by various warlords, some of whom were nobles and officials of the Han imperial court. The warlord Cao Cao took control of Emperor Xian and his court in 196 and began gradually reunifying the empire. Cao Cao ostensibly operated under Emperor Xian's rule, though in reality the emperor was a hostage.

Cao Cao's efforts to reunify China were rebuffed at the Battle of Red Cliffs in 208–209, when his armies were defeated by the allied forces of Sun Quan and Liu Bei. The Han dynasty formally ended in 220 when Cao Cao's son and heir, Cao Pi, pressured Emperor Xian into abdicating in his favour. Cao Pi became the emperor of a new dynasty, Cao Wei. In response, Liu Bei established the Shu Han dynasty in 221 with himself as its emperor. Sun Quan founded the Eastern Wu dynasty in 222, first adopting the title of king and later declared himself emperor in 229. The period from the end of the Han dynasty in 220 to the reunification of China proper under the Western Jin dynasty in May 280 is known as the Three Kingdoms era in Chinese history.

The Jin dynasty or the Jin Empire, officially Jin, sometimes distinguished as the Sima Jin or the Two Jins, was an imperial dynasty in China that existed from 266 to 420. It was founded by Sima Yan, eldest son of Sima Zhao, who had previously been declared the King of Jin. There are two main divisions in the history of the dynasty. The Western Jin (266–316) was established as the successor to Cao Wei after Sima Yan usurped the throne from Cao Huan. The capital of the Western Jin was initially in Luoyang, though it later moved to Chang'an (modern Xi'an). In 280, after conquering Eastern Wu, the Western Jin ended the Three Kingdoms period and reunited China proper for the first time since the end of the Han dynasty.

From 291 to 306, a series of civil wars known as the War of the Eight Princes were fought over control of the Jin state which weakened it considerably. In 304, the dynasty experienced a wave of rebellions by non-Han ethnicities termed by exonym as "Five Barbarians". The "barbarians" went on to establish nonpermanent dynastic states in northern China. This helped to usher in the Sixteen Kingdoms era of Chinese history, in which states in the north rose and fell in rapid succession, constantly fighting both one another and the Jin. Han-Zhao, one of the northern states established during the disorder, sacked Luoyang in 311, captured Chang'an in 316, and executed Emperor Min of Jin in 318, ending the Western Jin era. Sima Rui, who succeeded Emperor Min, then reestablished the Jin dynasty with its capital in Jiankang (modern Nanjing), inaugurating the Eastern Jin (317–420).

The Conquest of Shu by Wei was a military campaign launched by the dynastic state of Cao Wei against its rival Shu Han in late 263 during the Three Kingdoms period of China. The campaign culminated in the fall of Shu Han and the tripartite equilibrium maintained in China for over 40 years since the end of the Eastern Han dynasty in 220. The conquest laid the foundation for an eventual reunified China under the Western Jin dynasty in 280.

Cao Cao (pronunciation; [tsʰǎʊ tsʰáʊ]; Chinese: 曹操; c. 155 – 15 March 220), courtesy name Mengde, was a Chinese statesman, warlord, and poet who rose to power during the end of the Han dynasty (c. 184–220), ultimately taking effective control of the Han central government. He laid the foundation for the state of Cao Wei (220–265), established by his son and successor Cao Pi, who ended the Eastern Han dynasty and inaugurated the Three Kingdoms period (220–280). Beginning in his own lifetime, a corpus of legends developed around Cao Cao which built upon his talent, his cruelty, and his perceived eccentricities.

Cao Cao began his career as an official under the Han government and held various appointments including that of a district security chief in the capital and the chancellor of a principality. He rose to prominence in the 190s during which he recruited his own followers, formed his own army, and set up a base in Yan Province (covering parts of present-day Henan and Shandong). In 196, he received Emperor Xian, the figurehead Han sovereign who was previously held hostage by other warlords such as Dong Zhuo, Li Jue, and Guo Si. After he established the new imperial capital in Xuchang, Emperor Xian and the central government came under his direct control, but he still paid nominal allegiance to the emperor. Throughout the 190s, Cao Cao actively waged wars in central China against rival warlords such as Lü Bu, Yuan Shu, and Zhang Xiu, eliminating all of them. Following his triumph over the warlord Yuan Shao at the Battle of Guandu in 200, Cao Cao launched a series of campaigns against Yuan Shao's sons and allies over the following seven years, defeated them, and unified much of northern China under his control. In 208, shortly after Emperor Xian appointed him as Imperial Chancellor, he embarked on an expedition to gain a foothold in southern China, but was defeated by the allied forces of the warlords Sun Quan, Liu Bei, and Liu Qi at the decisive Battle of Red Cliffs.

Cao Pi (pronunciation) (c.late 187 – 29 June 226), courtesy name Zihuan, was the first emperor of the state of Cao Wei in the Three Kingdoms period of China. He was the second son of Cao Cao, a warlord who lived in the late Eastern Han dynasty, but the eldest son among all the children born to Cao Cao by his concubine (later wife), Lady Bian. According to some historical records, he was often in the presence of court officials in order to gain their support. He was mostly in charge of defence at the start of his career. After the defeat of Cao Cao's rival Yuan Shao at the Battle of Guandu, he took Yuan Xi's wife, Lady Zhen, as a concubine, but in 221 Lady Zhen died and Guo Nüwang became empress.

On 25 November 220, Cao Pi forced Emperor Xian, the last ruler of the Eastern Han dynasty, to abdicate in his favour, after which on 11 December 220 he proclaimed himself emperor and established the state of Cao Wei. Cao Pi continued the wars against the states of Shu Han and Eastern Wu, founded by his father's rivals Liu Bei and Sun Quan, respectively, but did not make significant territorial gain in the battles. Unlike his father, Cao Pi concentrated most of his efforts on internal administration rather than on waging wars against his rivals. During his reign, he formally established Chen Qun's nine-rank system as the base for civil service nomination, which drew many talents into his government. On the other hand, he drastically reduced the power of princes, stripping off their power to oppose him, but at the same time, rendering them unable to assist the emperor if a crisis arose within the state. After Cao Pi's death, his successor Cao Rui granted him the posthumous name "Emperor Wen" and the temple name "Gaozu".

The nine-rank system, also known as the nine-grade controller system, was used to categorize and classify government officials by rank in Imperial China. Their accorded rank signified their status in the government hierarchy and the amount of wages they earned. Created by the politician Chen Qun in the state of Cao Wei during the Three Kingdoms, it was used until the Song dynasty, and similar ranking systems were also present in the Ming dynasty and Qing dynasty.

A similar system was also used in Korea. In Japan, the Twelve Level Cap and Rank System was adopted in 603 during the reign of Empress Suiko.