The alleged '571 Project' (
五七一工程, a homophone for 'armed uprising'
武起义) was a purported 1971 plan to assassinate Mao. After its failure, Lin Liguo, his father Marshal
林彪, and his mother
叶群 died in a plane crash over Mongolia on September 13, 1971 (
九一三事件) while reportedly fleeing to the Soviet Union — one of the most dramatic and disputed episodes of the Cultural Revolution.