 While the ROK 7th Infantry Division was being annihilated at Tokchon by the PVA 38th Corps , the ROK 8th Infantry Division was also being routed , at Yongwon by the PVA 42nd Corps . With the PVA 125th Division tying down the ROK 10th and 21st Infantry Regiment at Yongwon , the 124th and the 126th Division tried to infiltrate the ROK 8th Infantry Division 's rear by marching through the hills east of Yongwon . At 1 p.m. on November 25 , the ROK 16th Infantry Regiment to the ROK 8th Infantry Division 's rear spotted the two Chinese divisions at Maengsan , 20 km ( 12 mi ) south of the Yongwon . Surprised by this development , the ROK 8th Infantry Division ordered the 16th Infantry Regiment to block the Chinese advance while the ROK 10th and 21st Infantry Regiment were retreating from Yongwon . But before the order could be carried out , the Chinese struck first after learning their trap had been discovered . As the ROK 10th and 21st Infantry Regiment were retreating from Yongwon early in the morning of November 26 , the PVA 125th Division ambushed both ROK regiments , forcing the Koreans to abandon their heavy equipment and to scatter into the hills . Meanwhile , following the bonfires made by the Koreans for the cold weather , the PVA 124th Division overran a battalion from the ROK 16th Infantry Regiment and attacked the ROK 8th Infantry Division 's command post at Maengsan . With the entire division dispersed , the ROK 8th Infantry Division headquarters and the ROK 16th Infantry Regiment broke out of Maengsan on November 27 and retreated from the battlefield . 
