The Korean War began on 25 June 1950 when the North Korean Korean People's Army (KPA) crossed the 38th Parallel to invade South Korea. Acting under United Nations (UN) orders, the Division moved from its base in Japan to Korea between 5–18 July 1950 to join the Eighth United States Army. The division, then under the command of Major General William B. Kean, successfully completed its first mission by blocking the approaches to the port city Pusan. For this action, the Division received its first Republic of Korea Presidential Unit Citation. The division participated in the breakout from the Pusan perimeter commencing on 16 September and Eighth Army then began a general offensive northward against crumbling KPA opposition to establish contact with forces of the 7th Infantry Division driving southward from the Inchon beachhead. Major elements of the KPA were destroyed and cut off in this aggressive penetration; the link-up was effected south of Suwon on 26 September. On 23 September the Division was assigned to the newly activated US IX Corps. The UN offensive was continued northwards, past Seoul, and across the 38th Parallel into North Korea on 1 October. The momentum of the attack was maintained, and the race to the North Korean capital, Pyongyang, ended on 19 October when elements of the Republic of Korea Army (ROK) 1st Infantry Division and US 1st Cavalry Division captured the city. The advance continued, but against unexpectedly stiffening resistance. The Chinese People's Volunteer Army (PVA) entered the war on the side of North Korea, making their first attacks in late October. The UN forces renewed their offensive on 24 November before being stopped by the PVA Second Phase Offensive starting on 25 November. The division was forced to carry out a systematic withdrawal and ordered to take up defensive positions on the south bank of the Chongchon River on 30 November 1950. Eventually, these lines failed and Eighth Army suffering heavy casualties, ordered a complete withdrawal to the Imjin River, near the 38th Parallel.