The state reached its height during the reigns of its first two rulers, Marquess Wen of Wei and Marquess Wu of Wei. King Hui of Wei, the third ruler, concentrated in economical developments including irrigation projects at the Yellow River. Nevertheless its slow decline began with King Hui. Wei's advancement in the east was checked several times in series of battles including the Battle of Maling in 341 BC. In the west it lost the Xihe region (a pastoral and strategic area on the west bank of the Yellow River at the border of today Shanxi and Shaanxi province) to Qin, continuously under invasions from Qin thereafter.
Military prowess of Qin broke the coalition forces of the states of Wei and Han at the Battle of Yique in 293 BC after which both states would no longer muster enough forces to face Qin in any major operation.
It was conquered by Qin in 225 BC.
List of Wei rulers