 Despite the success of the Chinese First Phase Campaign , the UN planners still believed that China had not intervened in Korea on a large scale . The suddenness of the Chinese withdrawal in the face of a victory further reinforced this belief . Working on the assumption that only 30 @,@ 000 Chinese troops could remain hidden in the hills , General Douglas MacArthur ordered the bombing of the bridges over the Yalu River in an effort to cut off Chinese reinforcements . Confident that the UN air force could detect and disrupt any troop movements across the Yalu River , MacArthur launched the Home @-@ by @-@ Christmas Offensive on November 24 to rout the remaining Chinese and North Korean forces and to end the Korean War . 
