Korean War Time Line June 1950 to July 1953

6. Position of Forces in November 1950

After secretly crossing the Yalu River on 19 October, the PVA 13th Army Group launched the First Phase Offensive on 25 October, attacking the advancing U.N. forces near the Sino-Korean border. This military decision made solely by China changed the attitude of the Soviet Union. Twelve days after Chinese troops entered the war, Stalin allowed the Soviet Air Force to provide air cover, and supported more aid to China. After decimating the ROK II Corps at the Battle of Onjong, the first confrontation between Chinese and U.S. military occurred on 1 November 1950; deep in North Korea, thousands of soldiers from the PVA 39th Army encircled and attacked the US 8th Cavalry Regiment with three-prong assaults - from the north, northwest, and west - and overran the defensive position flanks in the Battle of Unsan. The surprise assault resulted in the U.N. forces retreating back to the Ch'ongch'on River, while the Chinese unexpectedly disappeared into mountain hideouts following victory. It is unclear why the Chinese did not press the attack and follow up their victory.

The UN Command, however, were unconvinced that the Chinese had openly intervened due to the sudden Chinese withdrawal. On 24 November, the Home-by-Christmas Offensive was launched with the U.S. Eighth Army advancing in northwest Korea, while the US X Corps were attacking along the Korean east coast. But the Chinese were waiting in ambush with their Second Phase Offensive. On 25 November at the Korean western front, the PVA 13th Army Group attacked and overran the ROK II Corps at the Battle of the Ch'ongch'on River, and then decimated the US 2nd Infantry Division on the UN forces' right flank.[193] The UN Command retreated; the U.S. Eighth Army's retreat (the longest in US Army history) was made possible because of the Turkish Brigade's successful, but very costly, rear-guard delaying action near Kunuri that slowed the PVA attack for two days (27-29 November). On 27 November at the Korean eastern front, a US 7th Infantry Division Regimental Combat Team (3,000 soldiers) and the U.S. 1st Marine Division (12,000-15,000 marines) were unprepared for the PVA 9th Army Group's three-pronged encirclement tactics at the Battle of Chosin Reservoir, but they managed to escape under Air Force and X Corps support fire - albeit with some 15,000 collective casualties.