British colonialism began under the pretense of policing the slave trade. Britain outlawed slavery in 1807 and pushed for forms of “legitimate commerce” such as palm oil and cotton, and in so doing developed an internal infrastructure to facilitate these markets. By the 1820s, the British had made connections with the Sokoto Caliphate, whose highly structured society, aristocracy, and religion struck colonial administrators as more “civilized” than the war‐torn groups they encountered in the South. With the discovery of quinine in the 1850s, colonial explorers and missionaries who had been unable to enter the southern interior due to risk of malaria began contacting a wider range of groups; the British then had treaties and trade policies in place throughout the North and the South.
In the 1850s, the British used trade policies to influence African politics, including deposing rulers who stood in the way of the lucrative palm oil trade. In the 1880s, competition with French colonial powers in Africa prompted a policy shift and in 1882 the northern and southern “protectorates” were established. During the Berlin Conference of 1884–1885, European leaders determined who had rights to what “spheres of influence.” The two protectorates were joined in 1914 under British governor‐general Frederick Lugard, and the Colony and Protectorate of Nigeria was established. 2014 marks Nigeria’s grand celebration of the 100th anniversary of the union between the northern and southern regions.
Lugard instituted a policy of indirect rule through native authorities, who collected taxes and performed other local administrative tasks. In the North, Lugard worked through the Fulani ruling classes, who used the British in order to retain their power and to acquire wealth. Because rulers were no longer accountable to their people, corruption and poverty spread.
Many Muslims began to see the Fulani leadership as pawns—a sentiment echoed today by members of Islamist movements towards northern leadership. British favoritism towards Muslims, combined with Hausa‐Fulani advances into the Middle Belt, led to widespread conversion to Islam.
At the same time, a rising African intelligentsia—graduates of Christian missionary schools—began to challenge British rule in the South. Christianity spread rapidly at the grassroots level from the 1860s onwards, in large part due to the mission education system. Colonial administrators encouraged conversion to Christianity in the South, especially Anglicanism, as part of their mandate to “civilize” Africa. Mission schools became training grounds for the intellectual, commercial, civic, and military elites, who tended to be promoted by the British colonial government and who would be at the forefront of the nationalist movement. However, at the insistence of Hausa‐Fulani leaders in the North, the British barred Christian missionaries from proselytizing there, which meant that Western education was limited to Nigeria’s South. It also resulted in a preponderance of Christians among Nigeria’s nationalists.
After WWII the British began to see that colonialism was no longer pragmatic in Nigeria, and responded to the protests from returned ex‐servicemen who had fought alongside the British in the war by instituting a series of changes meant to develop a federal government. In 1954, the Lyttleton Constitution cemented a federal system with three self-governing states under weak central control. This included a large northern state and smaller eastern and western states, which reflected the three regional units managed separately and differently by the colonial administration. While they loosely corresponded with major ethnic groups, the borders were not intended to demarcate ethnicity and they arbitrarily cut across ethnic and linguistic communities. As the British never prioritized fostering unity among Nigeria’s disparate peoples, colonialism left Nigeria deeply divided.
For Nigerians, access to colonial resources was determined by the relative strength of their identity groups in relation to British power, and this fostered competition. In the South, Nigerians had benefited from missionary education and saw economic growth, urbanization, and the rise of a skilled middle class. Christianity dominated, though there were significant Muslim and indigenous religious communities as well. The larger but more insular North had extensive agricultural production, little access to Western education and rampant poverty. Mutual distrust was pervasive on the eve of independence.
 Adiele E. Afigbo, “Background to Nigerian Federalism: Federal Features in the Colonial State,” Publius, Vol. 21, No. 4 (1991), pp. 13–29.
"Frederick John Dealtry Lugard, Vanity Fair, 1895," Vanity Fair, modified from Wikimedia Commons.