King Zhaoxiang of Qin
Because King Zhaoxiang had not yet legally come of age (traditionally at the age of 20), his mother, who was now known as Queen Dowager Xuan, became the regent. She was supported by her brothers, Wei Ran and Mi Rong (羋戎), as well as two other sons, Prince Yi (公子悝) and Prince Fu (公子巿), the four of them collectively known as the "Four Nobles" (四貴).
King Zhaoxiang of Qin
In 283 BC, King Zhaoxiang offered to trade 15 cities in exchange of the jade disc of He, which was in the state of Zhao's possession. King Huiwen of Zhao was attracted by the offer and agreed to the trade. However, the Zhao ambassador Lin Xiangru (藺相如) figured out that Qin never meant to hold up their end of the deal, and managed to return the jade back to Zhao. During the following three years (282 BC to 280 BC), Qin attacked Zhao multiple times, capturing cities such as Shicheng (石城), Lin (藺), Lishi (離石), Qi (祁) and Guanglang (光狼城), killing 20,000 men, and forcing Zhao to agree to send hostages and concede lands in exchange for returning the captured cities. During the armistice meeting held at Mianchi (澠池), King Zhaoxiang attempted to humiliate King Huiwen, but was forced to back down when Lin Xiangru threatened to physically harm the Qin king.