Query: Who ignored the direct participation of the Soviet Union to prevent expanding the Korean War to the Soviet Union?
Context: Fearful of confronting the United States directly, the Soviet Union denied involvement of their personnel in anything other than an advisory role, but air combat quickly resulted in Soviet pilots dropping their code signals and speaking over the wireless in Russian. This known direct Soviet participation was a casus belli that the UN Command deliberately overlooked, lest the war for the Korean peninsula expand to include the Soviet Union, and potentially escalate into atomic warfare.