 Hoping to repeat the success of the earlier First Phase Campaign , the Chinese 13th Army first launched a series of surprise attacks along the Ch 'ongch 'on River Valley on the night of November 25 , 1950 , effectively destroying the Eighth United States Army 's right flank while allowing Chinese forces to move rapidly into UN rear areas . In the subsequent battles and withdrawals during the period of November 26 to December 2 , 1950 , although the US Eighth Army managed to avoid being surrounded by Chinese forces , the Chinese 13th Army were still able to inflict heavy losses onto the retreating UN forces which had lost all cohesion . In the aftermath of the battle , the US Eighth Army 's heavy losses forced all UN forces to evacuate North Korea and to withdraw to the 38th parallel . 
