Battle of Unsan

North Korea was in retreat by October 1950. After breaking out of the Pusan Perimeter at the south-east tip of the Korean peninsula in September, the UNC offensive pursued the Korean People's Army (KPA) through South Korea, into North Korea, and toward the Sino-Korean border. The US 1st Cavalry Division entered Pyongyang on 19 October, while the ROK were rushing towards the Yalu River in all directions. 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. In response to the rapid KPA collapse and the UNC advance toward the Chinese border, Chairman Mao Zedong ordered the People's Liberation Army's North East Frontier Force to be reorganized into the People's Volunteer Army (PVA) for the upcoming intervention in Korea. Mao was determined to prevent a North Korean capitulation, but the Chinese military was skeptical of its ability to fight more-modernized US forces. Mao compromised with the First Phase Campaign, a bridgehead building operation with limited offensives against South Korean forces while avoiding US forces. Under strict secrecy, the PVA entered Korea on 19 October. ==Prelude==

Locations and terrain Unsan is a town in northwest Korea, and it is located from the Ch'ongch'on River mouth on the Korean west coast. Forces and strategy Acting on Milburn's instruction, the ROK 1st Infantry Division advanced north on 24 October with the ROK 6th Infantry Division on its right and the US 24th Infantry Division on its left, and by the morning of 25 October, the ROK 1st Infantry Division had captured Unsan. But with the UNC spread thinly across Korea, a gap was left between the US 24th Division and ROK 1st Division, leaving the ROK left flank unprotected. Simultaneously, the bulk of the 40th Corps, together with the PVA 38th Corps and one division from the 42nd Corps, would attack and destroy the ROK 6th and 8th Infantry Divisions at the east of Unsan. To obscure troop movements and to prevent UNC air raids, the Chinese also started several forest fires around the end of October. ==Battle==

Initial skirmish On 25 October at 10:30, the ROK 1st Infantry Division attacked north with its 12th Regiment on the western bank of Samtan River while the 15th Regiment was trying to reach the eastern bank. The South Koreans first believed the resistance to be the last remnants of the KPA, but the perception soon changed with the capture of the first Chinese prisoner of the war. The prisoner revealed that there were 10,000 Chinese soldiers waiting to join the fight north of Unsan. The South Koreans soon found themselves in a seesaw battle with the PVA 360th Regiment during the night of 25 October. The next day, the PVA 39th Corps arrived at the west of Unsan, while cutting the road between Unsan and Yongsan-dong, completely surrounding the ROK division. Despite the warnings given by Brigadier General Paik Sun Yup, commander of the 1st Infantry Division, With the fighting reached a stalemate at Unsan, General Walton Walker of the Eighth United States Army ordered the US 8th Cavalry Regiment of the US 1st Cavalry Division to resume offensives north by relieving the ROK 12th Regiment. By the time the US 8th Cavalry Regiment reached Unsan on 29 October, the ROK 11th Infantry Regiment, 1st Infantry Division, was also pulling out of Unsan. Unsan had now become a northern salient in the UN line containing only the US 8th Cavalry Regiment and the ROK 15th Infantry Regiment. The Chinese plan called for the PVA 117th Division to attack from the northeast, the 116th Division to attack from the northwest and the 115th Division to attack from the southwest. The lack of UN manpower, however, created a gap between the 1st and 2nd Battalions. ambushing the UN forces at the road junction by 02:30. abandoning most of their vehicles and heavy weapons along the way. A surprise attack set many vehicles on fire, while causing numerous casualties among the Americans, most of whom were still sleeping. By the time the confusing fighting ended, the 3rd Battalion had been squeezed into a wide perimeter by the PVA 345th Regiment, 115th Division. The US 5th Cavalry Regiment made repeated attempts to rescue the 3rd Battalion by attacking the PVA 343rd Regiment at Bugle Hill, but after suffering 350 casualties, the 5th Cavalry was forced to withdraw under orders from Major General Hobart Gay, commander of the US 1st Cavalry Division. The trapped 3rd Battalion endured days of constant attacks; the survivors managed to break out of the perimeter by 4 November. By the end of the battle, less than 200 men of the 3rd Battalion managed to reach UN lines. ==Aftermath==

Immediately after the success at Unsan, the rest of the Chinese forces advanced across the US lines, intending to push the US forces back across the Ch'ongch'on River and into Pyongyang. But food and ammunition shortages soon forced the Chinese to disengage on 5 November, thus ending the Chinese First Phase Campaign. In return, the Chinese had suffered 10,700 casualties by the end of the Chinese First Phase Campaign. The Battle of Unsan has been considered to be one of the most devastating US losses of the Korean War. The Chinese victory at Unsan was as much of a surprise to the Chinese leadership as it was to the UN forces. The accidental encounter between the Chinese and US forces at Unsan eased the fear of the Chinese leadership about intervening in Korea, while the performance of the US 1st Cavalry Division was studied in great detail by Chinese commanders. PVA Commander Peng Dehuai incorporated the lessons from Unsan for the upcoming Second Phase Campaign, while General Douglas MacArthur launched the Home-by-Christmas Offensive under the assumption that only a weak Chinese force was present in Korea, resulting in the decisive battles at the Ch'ongch'on River and the Chosin Reservoir later that year. ==Notes==