Sima Yan Establishes the Western Jin Dynasty Summary

  • Last updated on November 11, 2022

Sima Yan attempted to use the establishment of the Western Jin Dynasty to unify China.

Summary of Event

The period after the fall of the Han Dynasty in 220 c.e. was one of great political and social chaos. The old empire was fractured by a series of internal uprisings and invasions by nomadic tribes from central and northern Asia. With the defeat of the forces of Cao Cao (Ts’ao Ts’ao; 155-220 c.e.) at the Battle of Red Cliffs (208 c.e.), China’s chance for reunification ended. The old empire broke apart, and this political breakdown ushered in the Three Kingdoms Period (220-280 c.e.), in which China divided into the Wei, Wu, and Shu Han Dynasties. This period witnessed a renewed interest in the martial arts, especially in the areas of military philosophy and strategy. This was an era of great turmoil but also one of significant intellectual accomplishment. Scholars created a vast number of written works that reflected the uncertainty and violence of the period. These treatises focused on the development of new tactical and strategic doctrines that reflected the emphasis placed on the use of cavalry formations by general Cao Cao during the decline and fall of the Han Dynasty. Sima Yi Sima Yan

The Three Kingdoms Period also witnessed a rise in the practice of Buddhism. Merchants and missionaries who traveled along the Silk Road initially brought this South Asian belief system to China. As social conditions declined, many of China’s intellectual elite looked for alternatives to their traditional Confucian model. Buddhism provided an optimistic alternative centered on the belief that a life based on strong ethical principles would be rewarded.





This is the world in which the Sima family rose to prominence. Sima Yan’s grandfather, Sima Yi, began the family’s quest for power as a military bureaucrat for the state of Wei. He became prominent at the royal court as the result of a number of important military victories against the northern nomadic tribes and other rivals of the state of Wei who coveted the rich agricultural land under its control. Sima Yi acquired his political and military skill serving as an adviser to general Cao Cao. When Cao Cao died, his son Cao Pei (Ts’ao P’ei; 187-226 c.e.) openly broke with the Han Dynasty and created the state of Wei. Sima Yi would prove to be Cao Pei’s most reliable and successful general, scoring victory after victory on behalf of his emperor for the next two decades.

Sima Yi’s sons inherited their father’s position after his death, and they proved to be just as successful in their military accomplishments. Most important, they led a successful campaign against the Shu Han Dynasty and were rewarded with aristocratic status. The family grew in prominence and created a power base that would eventually allow the Sima family to challenge the emperor for control of the state.

Sima Yan (Jin Wudi) rose to power in 265 c.e. when he forced the emperor of Wei to abdicate. He then declared that he had received the mandate of heaven (a divine authority to rule) and became the first emperor of the Western Jin Dynasty (265-316 c.e.). Sima Yan’s rise to power, like that of his grandfather, was based on his great military skill. In the preceding decade, Sima Yan had led a large expeditionary force exceeding 200,000 men in a successful campaign against the Wu Dynasty. His great victory was based on the successful implementation of a number of military technologies that enhanced the impact of light horse cavalry that had been introduced into Chinese warfare a generation earlier.

Advances in metallurgy allowed for the creation of lighter and stronger weapons and armor. When the Chinese cavalry went into battle, both the warrior and his horse were protected with armor that made it almost impossible to stop their assault. Sima Yan’s cavalry also took advantage of a new, important piece of equipment, the stirrup. This allowed the mounted warrior, moving at speeds up to 25 miles (40 kilometers) per hour, to attack any formation—or any opponent—at a full gallop. Until the invention of the stirrup, the cavalry had been used as moving artillery, essentially archers on horseback. The stirrup allowed cavalry to be used to break infantry formations without the fear of the rider being knocked off his horse by the force generated by the impact of a handheld weapon hitting its target. Sima also supported the growth of a professional military class. These hereditary warriors became a social institution set apart from the rest of society. They were permanent members of the military establishment subjected to regular training; individual positions within the military were passed on to the eldest son on the death of his father.

The world inherited by the Western Jin Dynasty was one ravaged by civil war. Years of fighting had destroyed the basic infrastructure, and Sima Yan was continually facing challenges to his power. Sima reacted to this by adapting the Legalist model for his government. This theory was based on the belief that people were basically bad and if left on their own would always choose selfish interests over the well-being of the community. Practitioners of Legalism established a strict legal code and enforced it by executing harsh punishments on anyone who broke the law. Sima also instituted the practice of creating a number of feudal estates and distributing them to his relatives as insurance against anyone’s challenging his power.


The success of the Western Jin Dynasty was short-lived. The incessant warfare prevented the dynasty from instituting measures that would provide enough security to reestablish a strong, well-functioning economy. The dynasty was also cursed with a series of weak, inefficient emperors who would be manipulated by military strongmen for personal gain. In time, the dynasty would splinter and another attempt at the reunification of China would be thwarted.

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Gernet, Jacques. A History of Chinese Civilization. New York: Cambridge University Press, 1990. The best single-volume account of Chinese cultural history. Maps, index, and bibliography.
  • citation-type="booksimple"

    xlink:type="simple">Graff, David A. Medieval Chinese Warfare, 300-900. New York: Routledge, 2002. An excellent overview of medieval military history. Maps, index, and bibliography.
  • citation-type="booksimple"

    xlink:type="simple">Graff, David A., and Robin Higham. A Military History of China. Boulder, Colo.: Westview Press, 2002. The best survey of Chinese military history on the market. Maps, index, and bibliography.
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