In 1963, the government of Congo-Brazzaville was taken over by Alphonse Massamba-Débat https://en.wikipedia.org/wiki/Alphonse_Massamba-D%C3%A9bat, the first African head of state to identify as a Marxist. During his rule, the Congo began to industrialize and the people's standard of living improved.
However, Massamba-Débat attempted to form popular militia units with Cuban assistance, triggering military mutinies in mid-1966. There was a failed coup attempt; two years later, Massamba-Débat ordered the imprisonment of Captain Marien Ngouabi https://en.wikipedia.org/wiki/Marien_Ngouabi, only to be forced to provide amnesty to all his political opponents.
On 4 September 1968, Ngouabi overthrew Massamba-Débat in a coup, establishing the People's Republic of Congo. Massamba-Débat was later executed on 25 March 1977. #history