evidence: After two months, the Republic of Korea Army (ROKA) and its allies were nearly defeated, holding onto only the Pusan Perimeter. In September 1950, however, UN forces landed at Inchon, cutting off KPA troops and supply lines. They invaded North Korea in October 1950 and advanced towards the Yalu River—the border with China. On 19 October 1950, the Chinese People's Volunteer Army (PVA) crossed the Yalu and entered the war.[39] UN forces retreated from North Korea in December, following the PVA's first and second offensive. Communist forces captured Seoul again in January 1951 before losing it two months later. Following the abortive Chinese spring offensive, they were pushed back to the 38th parallel, and the final two years of the fighting turned into a war of attrition.