Battle of Changping The Battle of Changping ( ) was a military campaign that took place during the Warring States period in China . It concluded in 260 BC with a decisive victory by the State of Qin over the State of Zhao , and ultimately allowed Qin to conquer and unify China decades later . The campaign is considered one of the most lethal military operations in history , although most of the Zhao casualties were captured soldiers executed after the battle . Qin invasion of Shangdang . Qin invaded the State of Han in 265 BC to capture the Commandery of Shangdang , now in modern - day southeastern Shanxi province . Shangdang was strategically placed west of Zhao and its capture would open an invasion route into Zhao . Within four years , the Qin army isolated the commandery from the rest of Han by capturing the main roads and fortresses across the Taihang Mountains . Shangdang was poised to fall . Rather than see Qin take Shangdang , Han offered the commandery to Zhao . King Xiaocheng of Zhao ( ) accepted and dispatched Lian Po and an army to secure the strategic territory from the encroaching Qin . The Zhao army met the Qin army , led by Wang He , in 262 BC at Changping , south of Shangdang . The Zhao suffered several minor defeats during initial confrontation with the Qin forces . Having assessed the enemy , Lian Po decided the only way to defeat the Qin was to wait them out , as Changping was much farther away from Qin territory than Zhao thus it would be more exhaustive to the Qin supply lines . The Zhao build several fortresses in the summer of 260 BC and then waited for the Qin to go away . The Qin managed to breach the defences once but did not have the strength or equipment to exploit it ; nonetheless , the Qin refused to leave . A three year stalemate ensued . A new strategy . The Qin sent agents into Zhao and Han to spread accusations that Lian Po was too cowardly and old to fight . King Xiaocheng of Zhao was already dissatisfied with Lian Po ' s strategy . Lian Po was replaced by Zhao Kuo , son of famous and deceased Zhao general , Zhao She . At the same time , the Qin secretly replaced Wang He with the renowned general , Bai Qi . According to legend , a dying Zhao She told his wife never to let Zhao Kuo command an army . When Zhao Kuo was appointed general , Lady Zhao and minister Lin Xiangru could not persuade King Xiaocheng to cancel the appointment . However , Lady Zhao extracted a promise from the king that the Zhao clan would not be punished if Zhao Kuo failed . Zhao defeated . Zhao Kuo assumed command in July 260 BC of an army reinforced to approximately 400 , 000 men . Zhao Kuo took part of his army and attacked the Qin camp . Bai Qi responded with a Cannae manoeuvre . The first group of the Qin army withdrew toward the Qin fortress and drew Zhao Kuo after them . The second group of 25 , 000 cavalry , and 5 , 000 light cavalry with bows and crossbow s , remained behind to spring the trap . When the Zhao attack reached the Qin fortress , the Qin cavalry ambush ed the Zhao Kuo ' s rear while the Qin light cavalry surrounded the Zhao fortress . With the enemy trapped Bai Qi ordered the Qin to counter - attack . The Zhao army was split in two and its supply lines cut . Zhao Kuo was unable to continue his attack or return to the Zhao fortress ; his army dug in on a hill and awaited relief . Since 295 BC , Zhao foreign policy had been dominated by opportunism and had frequently shifted between " hezong " ( ) ( anti - Qin alliances ) and " lianheng " ( ) ( pro - Qin alliances ) . Thus , as the battle in Changping unfolded , Zhao was unable to secure support from either the State of Chu or the State of Qi . King Zhaoxiang of Qin used this opportunity to mobilize additional forces against Zhao from Henei , in modern - day Henan province ; he bestowed one grade of noble rank to the population and ordered all men over the age of 15 to Changping to bolster the encirclement . Zhao Kuo hill fortification was be siege d for 46 days . In September , having run out of food and water , his desperate army made several unsuccessful attempts to breakout . The general was killed by Qin archers while leading his best troops . The Zhao army finally surrendered . Aftermath . Bai Qi ordered the captured soldiers to be executed , presumably by being buried alive ; the local population was hostile to Qin rule and he was afraid the captured soldiers would revolt . 240 of the youngest soldiers were released to spread terror in Zhao . Sima Qian claimed over 450 , 000 Zhao soldiers were killed during and after the battle . Emperor Xuanzong of Tang later built a temple over a collection of some of the human remains , and bones continue to be discovered on the site . Prior to the campaign , Zhao was one of the most powerful of the Warring States . The campaign addressed the immediate Qin threat as three years of war had financially and domestically exhausted both states . However , Zhao never recovered from the defeat , which allowed Qin to gain military dominance over the other states . In 230 BC , Qin would use this dominance to unify China . In popular culture . The 2004 Chinese television series " Tiexue Changping " is based on the battle . The battle also features as background to the events taking place in the manga Kingdom .