French colonization at the beginning of the 20th century brought legal prohibitions against slavery and an end to interclan warfare. During the colonial period, the population remained nomadic, but sedentary black Africans, whose ancestors had been expelled centuries earlier by the Moors, began to trickle back into southern Mauritania. As the country gained independence in 1960, the capital city of Nouakchott was founded at the site of a small colonial village. Ninety percent of the population was still nomadic. With independence, larger numbers of ethnic Sub-Saharan Africans (Haalpulaar, Soninke, and Wolof) entered Mauritania, moving into the area north of the Senegal River. Educated in French, many of these recent arrivals became clerks, soldiers, and administrators in the new state.

Moors reacted to this change by trying to Arabicize much of Mauritanian life, such as law and language. A schism developed between those who considered Mauritania to be an Arab country (mainly Moors) and those who sought a dominant role for the Sub-Saharan peoples. The discord between these two conflicting visions of Mauritanian society was evident during intercommunal violence that broke out in April 1989 (the "1989 Events"). It has since subsided. However, the tension between these two visions remains. A significant number from both groups, however, seeks a more diverse, pluralistic society.