When Brière de l'lsle arrived in Senegal as governor in 1876, Senegal was still largely a collection of commercial posts, but France ruled about 200,000 people. The population of the communes was almost twice what it had been in 1848, trade had increased, and peasant production was expanding on the mainland. French trade with Kajoor hit 3 million francs a year in 1874. Millet, cotton and peanuts were being traded in the upper Senegal river area. Brière picked up where Faidherbe left off. In a series of military and diplomatic efforts, he tightened control over the Senegal river, the peanut basin and the Guinea coast. He also initiated a railroad project that began the occupation of the Sudan.

Early in 1880, Naval Minister Admiral Jauréguiberry asked the Chamber of Deputies to approve construction of three linked railroads: one from Dakar to Saint Louis, a second connecting the Senegal and Niger rivers, and a third linking the other two railroads. Work was to start almost immediately on the first two. Going through areas not under French sovereignty, these projects required military control.