[10] As part of the Thanksgiving Offensive to end the war, Major General Frank W. Milburn, commander of US I Corps, ordered the ROK 1st Infantry Division to secure the Sui-ho Dam on the Yalu River by advancing through Unsan.

[12] Mao was determined to prevent a North Korean capitulation, but the Chinese military was skeptical of its ability to fight more-modernized US forces.

[15] Unsan is a town in northwest Korea, and it is located 50 mi (80 km) from the Ch'ongch'on River mouth on the Korean west coast.

[2]: 680 Upon noticing the thinly held UNC frontline, the Chinese decided to launch a pincer movement against the South Koreans at Unsan.

[18] Undetected by UNC intelligence, the 120th Division arrived at the blocking position on 24 October, with its 360th Regiment heavily fortified the hills north of Unsan.

[19] To obscure troop movements and to prevent UNC air raids, the Chinese also started several forest fires around the end of October.

[21] Faced with the sudden appearance of overwhelming Chinese forces, the ROK 1st Infantry Division tried to establish defensive positions by capturing the hills around Unsan.

[22] Aided by airdrops, the US 6th Medium Tank Battalion and the US 10th Anti-Aircraft Artillery Group, the 1st Infantry Division reopened the road on 27 October.

[2]: 694–5  As the UN forces began to buckle around Unsan, Milburn finally ordered the garrison to withdraw after learning of the destruction of the ROK 6th Infantry Division on the right flank.

[2]: 696–7  With the attacks gaining momentum, the PVA 348th Regiment, 116th Division, advanced southward from Unsan,[32] ambushing the UN forces at the road junction by 02:30.

[2]: 698–700  With all the roads blocked, the US 8th Cavalry Regiment's 1st and 2nd Battalions had to escape by infiltrating the Chinese lines in small groups,[33] abandoning most of their vehicles and heavy weapons along the way.

[7] For the UN forces, on the other hand, despite the heavy losses suffered by the US Eighth Army at Unsan, the unexpected Chinese withdrawal made the United Nations Command believe that China did not intervene in Korea on a large scale.

[41] PVA Commander Peng Dehuai incorporated the lessons from Unsan for the upcoming Second Phase Campaign,[42] while General Douglas MacArthur launched the Home-by-Christmas Offensive under the assumption that only a weak Chinese force was present in Korea,[43] resulting in the decisive battles at the Ch'ongch'on River and the Chosin Reservoir later that year.