Muhammed Bello, the second Sultan. Ribats were established, founding a number of new cities with walled fortresses, schools, markets, and other buildings. These proved crucial in expansion through developing new cities, settling the pastoral Fulani people, and supporting the growth of plantations which were vital to the economy. By 1837, the Sokoto state had a population of around 10-20 plus million people, becoming the most populous empire in West Africa. Decline European attention had been focusing on the region for colonial expansion for much of the last part of the 19th century. The French in particular had sent multiple exploratory missions to the area to assess colonial opportunities after 1870. French explorer Parfait-Louis Monteil visited Sokoto in 1891 and noted that the Caliphate was at war with the Emir of Argungu, defeating Argungu the next year. Monteil claimed that Fulani power was tottering because of the war and the accession of the unpopular Caliph Abderrahman dan Abi Bakar. However, following the Berlin Conference, the British had expanded into Southern Nigeria, and by 1901 had begun to move into the Sokoto Caliphate while simultaneous German efforts occurred in Cameroon. British General Frederick Lugard used rivalries between many of the emirs in the south and the central Sokoto administration to prevent any defense as he worked toward the capital, while the Germans conquered Adamawa. As the British approached the city of Sokoto, the new Sultan Muhammadu Attahiru I along with Muhammad bin Anabwani organized a quick defense of the city and fought the advancing British-led forces. The British force quickly won, sending Attahiru I and thousands of followers on a Mahdist hijra. Muslim supporters and officials moved from Hausaland, Segu, Massina and Adamawa towards to Burmi, a military station on the far-eastern border of the Empire. The mass migrations was foretold by Shehu Uthman Dan Fuduye a century before. The now shattered Caliphate was partitioned by Britain and Germany. On March 13, 1903, at the grand market square of Sokoto, the last Vizier of the Caliphate officially conceded to British Rule. The British appointed Muhammadu Attahiru II as the new Caliph. Fredrick Lugard abolished the Caliphate, but retained the title Sultan as a symbolic position in the newly organized Northern Nigeria Protectorate. This remnant became known as "Sokoto Sultanate Council". In June 1903, the British defeated the remaining forces of Attahiru I in an engagement where he was killed in action; by