The Muslim social movement known as the fergo Nioro provides a case of popular elaboration of the message of a leader of jihad. Umar Tal's call to holy war led to the conquest of Karta in the mid-1850s, and his call to hijra resulted in the migration of perhaps 20,000 Senegal-valley Fulbe to form a Muslim settler community. In the years after Umar's departure from Karta in 1859, military leaders and others in the Fulbe settler community sent envoys to recruit additional settlers from the Senegal valley. At least 16,000 and perhaps as many as 30,000 Fulbe responded to this recruitment effort and left Bundu, Futa Toro and the lower Senegal valley between 1862 and 1890. Two periods of more massive migration coincided with the residence at Nioro of Amadu Sheku, Umar's son and designated successor. During the late 1860s and early 1870s, a cholera epidemic swept up the Senegal valley, claimed thousands of victims, and encouraged Fulbe to leave the region for Karta. During the mid-1880s, French policies in the Senegal valley, notably the emancipation of slaves and moves to halt Fulbe raids in the lower Senegal valley, influenced the social movement.
In both periods of large-scale migration and at other times, the Umarian envoys constructed an appeal which elaborated and even transformed Umar's call to hijra. Umar's insistence on holy war was a dominant theme in all periods, and resonated with the young men who left the valley in hopes of accumulating wealth through warfare. His condemnation of French influence in the Senegal valley was also expressed in the Arabic letters delivered by envoys. Umar's emphasis on the cutting of social bonds was not emphasized, as Fulbe settlers sought to attract relatives and neighbors to the new Fulbe communities in Karta.