How did the Sokoto caliphate bring the Hausa states under one administration?

The Sokoto Caliphate unified the Hausa states by establishing a centralized politico-religious system under the leadership of Usman dan Fodio, who was proclaimed amīr al-muʾminīn ("commander of the faithful"). Following the success of the jihad, the former Hausa kingdoms were reorganized into autonomous emirates that pledged loyalty to the caliphate’s seat in Sokoto.12

To maintain this administration, the caliphate implemented several key structures:

• Administrative Oversight: Emirs were selected from the scholarly class and tasked with governing according to Islamic law.13
• Centralized Authority: While emirates enjoyed local autonomy, they contributed to the upkeep of Sokoto and referred internal or inter-emirate disputes to the caliph for settlement.1
• Division of Responsibility: In 1812, the administration was divided into two sectors: Muhammad Bello oversaw the eastern emirates from Sokoto, while Abdullahi dan Fodio managed the western emirates from Gwandu.32
• Communication: Officials frequently traveled between the capital and the provinces to oversee developments and ensure adherence to the caliphate's principles.1