函谷関
In 298 BC Zhao offered Qin an alliance and Lord Mengchang was driven out of Qin. The remaining three allies, Qi, Wei and Han, attacked Qin, driving up the Yellow River below Shanxi to the Hangu Pass. After 3 years of fighting they took the pass and forced Qin to return territory to Han and Wei. They next inflicted major defeats on Yan and Chu. During the 5-year administration of Lord Mengchang, Qi was the major power in China.