King Wuling of Zhao 趙武靈王 (r. 326-299) decided to retire and hand over the throne to his young son Prince He 何 (King Zhaowen 趙惠文王, r. 299-266). An older brother of the young king, Prince Zhang 公子章, rebelled against his unexperienced half-brother. Li Dui was entrusted to put down the rebellion on the side of Prince Cheng 公子成. Prince Zhang thereupon fled to Shaqiu 沙丘 (near modern Pingxiang 平鄉, Hebei) to the fortified mansion of the King Father (zhufu 主父). Li Dui pursued him and besieged the rebel and the retired king. The defenders ran out food and the King Father starved to death.
From then on Li Dui was the most powerful person in the state of Zhao and rose from the office of Minister of Justice (sikou 司寇) to that of counsellor (xiangguo 相國). He was also given the title of Lord of Fengyang 奉陽君.
His most important role in "international" respect was the cooperation with the famous coalition advisor Su Qin 蘇秦 in the creation of the alliance (meng 盟) of the five states Zhao, Chu 楚, Qi 齊, Wei 魏 and Han 韓 against Qin 秦. The joint army advanced to Chenggao 成皋 (near modern Xingyang 滎陽, Henan) but withdrew without having engaged Qin in battle.