The Fall of Wei, marking the end of one of the three major states of the Three Kingdoms period, was a significant event in the late 3rd century CE that reshaped the political landscape of ancient China. The decline and eventual collapse of the state of Cao Wei set the stage for the reunification of China under the Jin Dynasty, bringing an end to a period marked by war, political intrigue, and the division of the Chinese empire.

Cao Wei, established by Cao Pi following his father Cao Cao's consolidation of northern China, initially emerged as the strongest of the three kingdoms. However, over time, it faced a series of internal and external challenges that gradually weakened its power and stability.

Internally, the state of Wei experienced significant political turmoil and power struggles. The latter years of the Wei dynasty were marked by the increasing influence and control of the Sima family, particularly Sima Yi and his successors Sima Shi and Sima Zhao. These ambitious regents and generals gradually usurped power from the Cao family, leading to weakening imperial authority and internal discord.

Sima Yi's successful coup against the last powerful regent of the Cao family, Cao Shuang, was a turning point in the decline of Wei. This move effectively shifted the power dynamics within the state, paving the way for the Sima family's eventual control. The Sima clan's rise to power was marked by strategic political maneuvers and elimination of rivals, consolidating their influence over the state's affairs.

Externally, Wei faced continuous military pressure from its rival states, Shu Han and Wu. These conflicts drained resources and further stretched the capabilities of the Wei military, exacerbating the challenges faced by the state.

The final blow to the Wei dynasty came with Sima Yan (Sima Zhao's son) forcing the last Wei emperor, Cao Huan, to abdicate the throne in 265 CE. Sima Yan then proclaimed the establishment of the Jin Dynasty, declaring himself Emperor Wu. This marked not only the end of the Wei dynasty but also the beginning of the end for the Three Kingdoms period.

The fall of Wei signified the culmination of the gradual shift of power from the Cao family to the Sima clan. Under the Jin Dynasty, Sima Yan eventually succeeded in unifying China, bringing an end to the decades-long period of division and warfare that had characterized the Three Kingdoms era.