Mohamed Mahmoud entered the Mauritanian army in November 1960, the year of Independence and was trained in the French military academies. He then held various positions of responsibility in the government of Moktar Ould Daddah.
On April 6, 1979, Mohamed Mahmoud and Ahmed Ould Bouceif supported by Lieutenant-Colonel Mohamed Khouna Ould Haidalla and the new Military Committee for National Salvation (CMSN), overthrew Mustafa Ould Salek due to his loss of influence and power within the CMSN, and also due to many economic problems arising from the conflict in the Western Sahara and the growing gap between Arabs and black Africans in the country.