During the period of the War to Resist US Aggression and Aid Korea, why did Mao Zedong say that the United States threatened to use atomic bombs as a "paper tiger"?

{"v":1,"info":{"title":{"content":"抗美援朝时期，毛泽东为何说美国威胁动用原子弹就是“纸老虎”？","en":"During the period of the War to Resist US Aggression and Aid Korea, why did Mao Zedong say that the United States threatened to use atomic bombs as a \"paper tiger\"?"},"description":{"content":"中国人民志愿军在朝鲜战场上的第一次战役即将结束时，志愿军司令员兼政治委员彭德怀判断以美国为首的“联合国军”可能重新组织进...","en":"Chinese the first battle of the Volunteer Army in Korea was coming to an end, Peng Dehuai, commander and political commissar of the Volunteer Army, judged that the \"United Nations Army\" led by the United States might reorganize into ..."}},"items":[]}