During the liberation struggle in Mozambique, several actors competed to assert their leadership and vision on the future of the country, and some of them connected to diplomatic networks at continental and international level within the divisions of the decolonization processes in Africa and of the global Cold War. Thus, various political movements emerged before and after the formation of FRELIMO, and they aimed to be internationally recognized as legitimate representatives of the Mozambican people in the struggle against Portuguese colonialism. This article closely investigates the political trajectory that probably constituted the greatest challenge to FRELIMO as the ‘true’ and ‘authentic’ liberation movement in Mozambique: the path from the formation of the União Democrática Nacional de Moçambique (UDENAMO) to the constitution of the Comité Revolucionário de Moçambique (COREMO). This analysis enriches not only the historical framework of the liberation war, but also the scientific debate on nationalism in Mozambique and, therefore, on the cleavages that still undermine the political stability of the country.