The first and overwhelming impression of Sudan is its physical vastness and ethnic variety, elements that have shaped its regional history from time immemorial. The nation encompasses virtually every geographical feature, from the harsh deserts of the north to the rain forests rising on its southern borders. Like most African countries, Sudan is defined by boundaries that European powers determined at the end of the 19th century. The British colonial administration in Sudan, accomplished in 1899, emphasized indirect rule by tribal shaykhs and chiefs, although tribalism had been considerably weakened as an administrative institution during the Mahdist time .This loosening of loyalties exacerbated problems in governmental structure and administration and in the peoples' identification as Sudanese. To this day, loyalty remains separated among family, clan, ethnic group, and religion, and it is difficult to forge a nation because the immensity of the land permits many of Sudan's ethnic and tribal groups to live comparatively undisturbed by the central government.

The Sudanese of the south are of African origin. Islam has made only modest inroads among these followers of orthodox religions and of Christianity, which was spread in the twentieth century by European missionaries, and Arabic has not replaced the various languages of the south. The strong regional and cultural differences have inhibited nation building and have caused the civil war in the south that has raged since freedom, except for a time of peace between 1972 and 1983. The distrust between Sudanese of the north and those of the south--whether elite or peasants--has deepened with the long years of hostilities. And the cost of war has drained valuable national resources at the expense of health, education, and welfare in both regions.