美日安保條約
In 1958 a Maoist group split from the Communist Party advocating violent revolution. In 1959 the Zengakuren, where the violent radicals had concentrated, broke into the Diet of Japan during discussions of the Treaty of Mutual Cooperation and Security between the United States and Japan, eliciting praise from a segment of the Japanese population. It was widely noted that the Old Left had not taken any such extreme measures, and thus the New Left began its ascendance.