King Zhaoxiang of Qin
In 293 BC, East Zhou decided to ally itself with the states of Han and Wei, and sent troops to help attacking Qin. However, the combined forces of this alliance was destroyed at Yique by the young Qin general Bai Qi, with 240,000 men killed and their commander Gongsun Xi (公孫喜) captured and executed. After this loss, the East Zhou was unable to actively participate in future interstate struggles in any significant fashion.
In 256 BC, Duke Wu of West Zhou (西周武公) allied with other states to stop the Qin offensive on the Han city of Yangcheng. In retaliation, King Zhaoxiang of Qin sent general Jiu to invade West Zhou, successfully breaking into Wangcheng. The Duke Wu was taken to Xianyang to beg for mercy, conceding all his lands. Both King Nan and Duke Wu would die later that year, and the subsequent Duke of West Zhou, Duke Wen (西周文公), was exiled to Danhuju (憚狐聚). Because the Zhou royal court had fallen from power and King Nan had died without a successor, the Eastern Zhou Dynasty collapsed, ending 879 years of Zhou monarchy. The remaining East Zhou state was also conquered by Qin chancellor Lü Buwei seven years later in 249 BC during the reign of King Zhaoxiang's grandson King Zhuangxiang, after Duke Jing of East Zhou attempted to form an anti-Qin alliance with other states.
King Zhaoxiang of Qin
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 disgrunted 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.