evidence: The following month saw U.N. forces crossing the 38th parallel into North Korea, capturing Pyongyang, the capital of North Korea, and advancing to the Yalu River, the northern boundary of North Korea and China. In late October 1950, Chinese forces crossed into North Korea to aid their ally. By January 1951, Chinese and North Korean forces recaptured Seoul. [...] No peace treaty was ever signed between North and South Korea and in the decades since the Korean War, North Korean forces have conducted numerous cross-border incursions and other acts of aggression.