During the Warring States Period, the Battle of Changping broke out in 260 BC, which results in a decisive victory of the state of Qin over Zhao.

In 257 BC, the Qin invaded the Han. Responding to the Han call for help, the Zhao king decided to send Lian Po to deal with the threat. The two armies met at Changping, situated in the Northern part of the Han lands. On one side was the Qin army, led by renowned General Bai Qi, on the other was the Zhao army led by Lian Po. Lian Po, after looking over the Qin formations, decided that the only way to stop their attack was to wait it out. Thus he built several fortresses and camped there, waiting for the opposing army to go away or a peace treaty to be concluded by the Han and the Qin.

The Qin had no intention of leaving. They sent spies to the state of Zhao and Han, ordering them to spread the word that Lian Po was cowardly and was too old to fight battles. The king, upon hearing this, immediately decided to remove Lian Po and replace him with Zhao Kuo, the son of another famous Zhao general, Zhao She.

Legend has it that on his deathbed, Zhao She told his wife never to let Zhao Kuo command an army. So Zhao She's wife, after hearing of Zhao Kuo's appointment as general, went up to the King of Zhao and tried to persuade him not to let Zhao Kuo command an army, along with the minister, Lin Xiangru. The king turned their requests down.

When Zhao Kuo assumed command, he ordered the army to launch an invasion of the Qin camp. The Qin forces were already lying in wait for them and the Zhao forces were eventually driven up a hill which the Qin then besieged for 40 days. At last, driven mad by hunger and thirst, the Zhao forces made a desperate change down the hill, with Zhao Kuo leading. He was shot down by Qin archers.

The troops of Zhao were routed. Legends accounted for more than four hundred thousand Zhao prisoners of war massacred but such grossly overestimated number has been disputed.

With this victory, Qin had established military superiority over other states. More campaigns and battles ensued, especially in the conquest of the state of Chu. Nevertheless no matter how bloody these military operations would be, Qin's final victory was guaranteed.