During 1962–1965 a factional conflict surged within the Arab Nationalist Movement. Ibrahim was part of a tendency a within the Arab Nationalist Movement, including Nayef Hawatmeh, Mohammed Kishli, Bilal al-Hasan and Abdel Fattah Ismail, that became increasing inspired by the Cuban, Chinese and Vietnamese revolutions and began to gear towards Marxism. The radical group, to which Ibrahim belonged, stressed that national and social struggles should not be separated from each other. In 1966 the group around Ibrahim began publishing articles in Al-Hurriya, the organ of the Arab Nationalist Movement, that were critical of the government of the United Arab Republic. Ibrahim was the editor of Al-Hurriya. However, until 1967 the tendency of Ibrahim remained committed to Nasserism. The defeat of Egypt in the 1967 Six-Day War aggravated the divisions within the Arab Nationalist Movement, with the tendency of Ibrahim, Hawatmeh and Ismail moving from nationalism to Marxism-Leninism. In 1968 Ibrahim founded the Organization of Lebanese Socialists, which in 1970 merged with the group Socialist Lebanon to form the Communist Action Organization in Lebanon (OACL). In 1975 Ibrahim was named general secretary of OACL (hitherto the organization had a collective leadership), a post he was to occupy until his death.
