The UN resumed the offensive on 24 November, shortly before the PVA began their own Second Phase Offensive. The PVA 13th Army Group launched a series of surprise attacks on the night of 25 November, pushing the US Eighth Army back to the Chongchon River. The PVA inflicted heavy losses on the ROK and decimated the US 2nd Infantry Division on the right flank, as the US Eighth Army began a long retreat south. At the same time, the PVA 9th Army Group ambushed US X Corps near the Chosin Reservoir as the freezing winter weather set in. Although the US Eighth Army succeeded in avoiding encirclement, US X Corps had to be evacuated by sea from Hungnam during December 1950. MacArthur's forces were expelled from North Korea and withdrew to the 38th Parallel, where they sought to once again establish defensive positions. In reserve at the start of the renewed PVA offensive, the 27th British Commonwealth Brigade was spared the initial brunt. Yet the offensive soon forced the UN forces into a disorganised withdrawal. 3 RAR withdrew in nine days, arriving at Uijeongbu, north-east of Seoul, on 11 December 1950. There the British and Australians occupied defensive positions in an attempt to secure the northern approaches to the South Korean capital during the Battle of Uijeongbu.