Despite, or in the reading of several scholars partly because of, the hostility its exclusivity requirement provoked from established orders, the Tijaniyya became the largest Sufi order in West Africa within a few generations of its founding, a growth historians attribute in part to the same requirement that had made it controversial. A convert who could hold no competing affiliation became, in effect, wholly identified with the Tijani network into which they were initiated, and the order's specialized modern history describes this as producing unusually cohesive regional communities bound by a single shared chain of initiation rather than by overlapping and sometimes competing loyalties. Nineteenth century figures including al Hajj Umar Tal, whose West African campaigns are documented in the Corpus of Early Arabic Sources for that region's history, carried Tijani affiliation across Senegal, Mali and neighboring territory, and in the twentieth century the Senegalese teacher Ibrahim Niasse built on that same exclusive structure to make the order a mass movement reaching well beyond its original North African base. The order remains, by most estimates cited in modern scholarship on Sufism in the region, the largest single Sufi affiliation in West Africa today, a scale scholars connect directly to the disciplined, non overlapping membership its founder's exclusivity requirement produced from the order's earliest years in Fez.