On 25 June 1950, North Korea invaded South Korea, sparking the Korean War, the Cold War's first major conflict, which continued until 1953. At the time, the Soviet Union had boycotted the United Nations (UN), thus forfeiting their veto rights. This allowed the UN to intervene in a civil war when it became apparent that the superior North Korean forces would unify the entire country. The Soviet Union and China backed North Korea, with the later participation of millions of Chinese troops. After an ebb and flow that saw both sides facing defeat with massive losses among Korean civilians in both the north and the south, the war eventually reached a stalemate. During the war, Rhee's party promoted the One-People Principle (based on the German ideology of the ''Herrenvolk'') an effort to build an obedient citizenry through ethnic homogeneity and authoritarian appeals to nationalism.