The military of North Korea invaded the South on 25 June 1950, and swiftly overran most of the country. The United Nations Command (UNC) was subsequently established following the UN Security Council's recognition of North Korean aggression against South Korea. The motion passed because the Soviet Union, a close ally of North Korea and a member of the UN Security Council, was boycotting the UN over its recognition of the Republic of China rather than the People's Republic of China. The UNC, led by the United States, intervened to defend the South, and rapidly advanced into North Korea. As they neared the border with China, Chinese forces intervened on behalf of North Korea, shifting the balance of the war again. Fighting ended on 27 July 1953, with an armistice that approximately restored the original boundaries between North and South Korea, but no peace treaty was signed. Approximately 3 million people died in the Korean War, with a higher proportional civilian death toll than World War II or the Vietnam War, making it perhaps the deadliest conflict of the Cold War-era. In both per capita and absolute terms, North Korea was the country most devastated by the war, which resulted in the death of an estimated 12–15% of the North Korean population ( 10 million), "a figure close to or surpassing the proportion of Soviet citizens killed in World War II," according to Charles K. Armstrong. As a result of the war, almost every substantial building in North Korea was destroyed. Some have referred to the conflict as a civil war, with other factors involved.