He was born in the small village of Nkolo, Boko District, French Equatorial Africa, in 1921, into a Kongo family and was a member of the Lari tribe. He attended missionary school and primary schooling at the Boko Regional School. He then received training as a teacher at the Edouard Renard school in Brazzaville. By the age of 13, he was a teacher and went to teach in Chad from 1945 to 1948. By 1940, he had joined the anti-colonialist Chadian Progressive Party and served as the general secretary of the Association for the Development of Chad in 1945. In 1947, he moved back to Congo and was principal of a school in Mossendjo from 1948 to 1953, then in Mindouli from 1953 to 1956. He was also the headmaster of Bakongo Secular School in Brazzaville in 1957 and joined the Congolese Progressive Party.
The government of Massamba-Débat attempted to undertake a political economic strategy of "scientific socialism." By July 1964 Massamba-Débat's government had declared one-party rule under the National Movement of the Revolution and a campaign of nationalizations began. Internationally Massamba-Débat aligned his country with the USSR and Communist China and he allowed nominally communist guerrillas to base themselves on Congolese territory. The ideology of his regime was on the left and the Congo was closing in on countries of a socialist nature, especially Cuba and China, while moving away from capitalist countries. Che Guevara comes to meet Massamba-Débat in January 1965. Diplomatic relations were severed with the United States. Relations are strained with the neighboring Democratic Republic of the Congo, whose political path is increasingly influenced by mobutist ambitions. Consequently, the Tshombe government expels the citizens of Congo-Brazzaville who live in the former Belgian Congo. The culmination of this atmosphere of "terror" is the kidnapping and murder in February 1965 of three judicial personalities whose positions are not to the liking of the regime, the president of the Supreme Court Joseph Pouabou, the prosecutor Lazare Matsocota and the director of the Congolese Information Agency Anselme Massoueme to whom their degree of participation cannot be corroborated. Massamba-Débat also attempted to form popular militia units and in 1966 with the help of the Cuban army. For 10 days in June and July 1966 members of the military attempted to overthrow his government after he had attempted to place the military under a single command. In the failed coup attempt several hundred Cuban troops sheltered members of Massamba-Débat's government and he was eventually able to return to power after giving in to some of the coup leaders demands. On August 5, 1968, the new National Council of the Revolution was formed, along with a new government, with 40 members including Massamba-Débat. In July 1968, he arrested Captain Ngouabi, dissolved the National Assembly and the Political Bureau of the MNR and suspended the 1963 Constitution. This resulted in a confrontation between supporters of the Civil Defense and part of the army. He was then forced to amnesty all political prisoners and deal with his opponents. Following the coup tensions remained between Massamba-Débat's administration and the military and on September 4, 1968 Massamba-Débat's government was overthrown by Marien Ngouabi, the chairman of the same party that had brought Massamba-Débat to power.
Following the bloodless coup of 1968 Massamba-Débat was forced to leave politics and Massamba-Débat returned to his home town. A few hours after Ngouabi's assassination Massamba-Débat was placed under arrest. When Ngouabi was murdered in 1977, many people were arrested and tried for plotting the assassination, including Massamba-Débat. Massamba-Débat was executed on the night of March 25, 1977, by firing squad.
