General MacArthur, Commander in Chief of UN Forces, believed that the Chinese government’s threat to involve itself in the war in Korea was a bluff, but by 19 October 1950 some Chinese units were already in Korea. After UN forces consolidated their positions MacArthur ordered an advance along the front. The 8th Army advanced north for 24 hours until it was struck a massive blow mainly aimed at its right flank. Communist China ordered 200,000 troops of the People’s Volunteer Army to cross the border into Korea; UN forces were forbidden to undertake reconnaissance north of the Yalu River and failed to detect this move. Local attacks against UN positions began almost immediately, followed by a major counter offensive on the 25/26 November. UN forces retreated south, evacuating Pyongyang in early December and through the ports of Wosam and Hungnam in the northeast 10–25 December. On 17 December Kim Il-Sung was removed from command of Communist forces in Korea: China was now in command. The UN forces withdrew to a line approximately 130 miles (210 km) to the south of their November line of advance, approximately along the 38th parallel, which still included Seoul. The renewed Chinese-led offensive began on 1 January 1951; 400,000 Chinese and 100,000 North Korea troops attacked the 200,000-strong UN forces along the whole front. On 4 January Seoul changed hands for the third time. A combination of stubborn resistance by UN ground forces and air support from air forces operating from bases in Korea, Japan and the aircraft carriers of US 7th Fleet slowed the Communist offensive to a halt, reaching its furthest point south on 24 January 1951.
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