with Wei against Qin began in 287 BC, but ended in defeat at Huayang in 273 BC. The struggle then culminated in the bloodiest battle of the entire period, the Battle of Changping in 260 BC. Zhao's forces were utterly defeated by Qin. Although the forces of Wei and Chu saved Handan from a subsequent siege by the victorious Qin, Zhao would never recover from the enormous loss of troops in the battle.

In 229 BC, invasions led by the Qin general Wang Jian