Treatise on Armament Technology, Volume 9

...and they are about to surrender anyway." Consequently, the King of Zhao appointed Zhao Kuo to replace Lian Po Lian Po was a cautious, veteran general who favored defensive warfare; his replacement by the inexperienced Zhao Kuo is a classic historical example of a ruler choosing aggression over wisdom. as the commanding general. When the King of Qin heard that Zhao Kuo had taken command, he secretly sent the Lord of Wu'an Bai Qi, a brilliant and ruthless strategist who never lost a battle. to serve as the Senior General, making Wang He his deputy. He issued a strict order throughout the army: "Anyone who dares to leak word of my appointment shall be executed."

When Zhao Kuo arrived at the front, he completely changed the existing regulations and replaced the military officers, then led his forces out to attack the Qin army. The Lord of Wu'an feigned a retreat, then deployed two "ambush forces" Qibing (Ambush Forces): Strategic units kept in reserve for surprise flanking maneuvers rather than direct frontal assaults. to intercept them. Zhao Kuo, riding the momentum of his perceived victory, pursued them until he reached the Qin fortifications.

The fortifications were held firmly and he could not break through; meanwhile, the Qin ambush forces cut off his rear, splitting the Zhao army into two and severing their supply lines. The Lord of Wu'an sent out light infantry to harass them. The Zhao forces met with no success in battle and were forced to build their own fortifications, holding their ground while waiting for reinforcements.

When the King of Qin received word of this, he personally traveled to Henei and conscripted every male citizen aged fifteen and older to go to Changping.
These were the words of Yu Qing.

They blocked all Zhao reinforcements and food supplies. Zhao requested grain from Qi, but the King of Qi refused. The Zhao army was without food for forty-six days, and the soldiers turned to cannibalism. In desperation, they launched a fierce assault on the Qin ramparts, attempting to break out but failing. Zhao Kuo...