During the Warring States period, Wey steadily declined due to internal strife and pressure from neighbors, especially
Wei. In 346 BCE, the duke of Wey degraded his title to marquis (侯). By 320 BCE, the ruler further downgraded to
jun (君, lord), and Wey controlled only the county of
Puyang (濮陽). In 254 BCE,
King Anxi of Wei killed
Lord Huai of Wey (衛懷君). Two years later (252 BCE), Wei installed its son-in-law (from the Wey house) as
Lord Yuan of Wey (衛元君), making Wey a dependency of Wei. In 241 BCE (year 6 of King Zheng of Qin's reign), Qin captured Puyang during its attack on Wei, incorporating it into the new
Dong Commandery. Wey's ruler was relocated to
Yewang (野王), and a Ji clan member was appointed as
Lord Jiao of Wey (衛君角). Wey survived nominally as a Qin vassal with no real independence.
Traditional account (per
Shiji): Wey was overlooked during
Qin Shi Huang's unification in 221 BCE due to its insignificance. It endured until 209 BCE (year 1 of
Qin Er Shi), when Qin Er Shi deposed Lord Jiao, extinguishing Wey's line shortly before Qin's fall.
Modern scholarly revision: Japanese historian
Hirase Takao (平勢隆郎) argued in his
New Chronological Table of the Eastern Zhou in Shiji (1995) that
Shiji contains a ~12-year systematic error from calendrical differences (Qin's immediate-year accession vs. eastern states' next-year accession). Cross-checked with excavated sources like Shuihudi Qin bamboo slips and Tsinghua
Xinian, Lord Jiao's reign ended in 221 BCE, coinciding with Qin's conquest of Qi and full unification. Wey thus fell with the other states. This view is supported by Chinese scholar
Zhou Zhenhe (周振鶴) and resolves chronological inconsistencies. ==Vassals==