函谷关
In 299 BC, King Zhaoxiang invited Lord Mengchang to Qin with the intention of appointing him as chancellor. However, after hearing (perhaps ill-intended) warnings from his ministers that Lord Mengchang was still loyal to his home state of Qi (which had just soured its diplomatic relationship with Qin), King Zhaoxiang ordered Lord Mengchang to be put under house arrest. Desperate, Lord Mengchang sent a messenger to bribe King's Zhaoxiang's favourite concubine, who demanded a snow fox fur coat, which Lord Mengchang had already given to King Zhaoxiang as a gift when he first arrived and had to steal back from the royal vault. Thanks to the pleas of the concubine, Lord Mengchang was released within two days, and he quickly smuggled himself out of Qin, narrowly evading a small army that King Zhaoxiang had ordered to pursue him. In 298 BC, the disgruntled Lord Mengchang, who was now the newly appointed chancellor of Qi, lobbied for a combined force of Qi, Han and Wei and laid siege to the Qin fortification of Hangu Pass. The allied army managed to penetrate past the Hangu Pass all the way to Yanshi (盐氏), forcing Qin to negotiate an armistice that involved returning the previously occupied Fengling and Wusui back to Wei and Han.