From the mid-1950s, TANU and then, after independence in 1961, the government of Tanganyika (from 1964 Tanzania) supported the liberation of Africa from colonial domination and white-minority regimes. Dar es Salaam became then a key center of international politics around the national liberation struggles in Southern Africa in the 1960s and 1970s. In this way Nyerere intended to provide greater security to his country, and strengthen the political legitimacy of his government both at home and internationally. After analysing the particular diplomatic entanglements that developed around TANU and the government in Dar es Salaam, this chapter looks specifically at the role they played in relation to the liberation struggle in Mozambique. It examines the contested process of formation of FRELIMO in Dar es Salaam, the role played by Tanganyika/Tanzania and by the Liberation Committee of the Organization of African Unity in establishing FRELIMO as the only “authentic” liberation movement in Mozambique, and the dialectical relationship between the institutions of the “state in the making” of FRELIMO in Dar es Salaam and those of Nyerere’s government. In doing so, this chapter highlights not only the confluence of interests between the Tanganyikan/Tanzanian institutions and those of FRELIMO, but also the contradictions of this relationship and its intertwining with the variety of international interests that converged in Dar es Salaam.