Of the South Sudanese ethnic groups, the Dinka are the largest, Nuer the second largest, the Zande the third-largest and the Bari are the fourth-largest.

They are found in today's Maridi, Yambio, and Tombura districts in the tropical rainforest belt of Western Equatoria, the Adio of Azande client in Yei, Central Equatoria and Western Bahr el Ghazal.

Slavery has been an institution of Sudanese life throughout history.

The slave trade in the south has intensified in the nineteenth century, and has continued after the British have suppressed slavery in much of sub-Saharan Africa.

Annual Sudanese slave raids into non-Muslim territories result in the capture of countless thousands of southern Sudanese, and the destruction of the region's stability and economy.

The Azande have had good relations with the neighbors, namely the Moru, Mundu, Pöjulu, Avukaya, Baka and the small groups in Bahr el Ghazal, due to the expansionist policy of their king Gbudwe, in the eighteenth century.

In the nineteenth century, the Azande fight the French, the Belgians and the Mahdists to maintain their independence.

Egypt, under the rule of Khedive Isma'il Pasha, first attempts to control the region in the 1870s, establishing the province of Equatoria in the southern portion.

Christian missionaries, who operate schools and medical clinics, provide limited social services in southern Sudan.

The earliest Christian missionaries had been the Verona Fathers, a Roman Catholic religious order that had established southern missions before the Mahdiyah.

Other missionary groups active in the south include Presbyterians from the United States and the Anglican Church Missionary Society.

There is no competition among these missions, largely because they maintain separate areas of influence.

The government eventually subsidizes the mission schools that educate southerners.

Because mission graduates usually succeed in gaining posts in the provincial civil service, many northerners regard them as tools of British imperialism. 

few southerners who receive higher training attend schools in British East Africa (present-day Kenya, Uganda, and Tanzania) rather than in Khartoum, thereby exacerbating the north–south division.

The economic development of the Sudanese south, although it is potentially a rich agricultural zone, suffers because of the region's isolation.

Moreover, a continual struggle goes on between British officials in the north and south, as those in the former resist recommendations that northern resources be diverted to spur southern economic development.

Personality clashes between officials in the two branches in the Sudan Political Service also impede the south's growth.

Those individuals who serve in the southern provinces tend to be military officers with previous Africa experience on secondment to the colonial service.

They usually are distrustful of Arab influence and are committed to keeping the south under British control.

By contrast, officials in the northern provinces tend to be Arabists often drawn from the diplomatic and consular service.

Whereas northern provincial governors confer regularly as a group with the governor general in Khartoum, their three southern colleagues meet to coordinate activities with the governors of the British East African colonies.

British authorities treat Sudan's three southern provinces as a separate region.

The colonial administration, as it consolidates its southern position in the 1920s, detaches the south from the rest of Sudan for all practical purposes.

The period's "closed door" ordinances, which bar northern Sudanese from entering or working in the south, reinforces this separate development policy.

Moreover, the British gradually replace Arab administrators and expel Arab merchants, thereby severing the south's last economic contacts with the north.

The colonial administration also discourages the spread of Islam, the practice of Arab customs, and the wearing of Arab dress.

At the same time, the British make efforts to revitalize African customs and tribal life that the slave trade had disrupted.

Finally, a 1930 directive states that blacks in the southern provinces are to be considered a people distinct from northern Muslims and that the region should be prepared for eventual integration with British East Africa.

Some British colonial officials in southern Sudan had responded to the Sudan Administrative Conference by charging that northern agitation had influenced the conferees and that no voice had been heard at the conference in support of retaining the separate development policy.

These British officers had argued that northern domination of the south would result in a southern rebellion against the government.

Khartoum had therefore convened a conference at Juba to allay the fears of southern leaders and British officials in the south and to assure them that a post-independence government would safeguard southern political and cultural rights.

Despite these promises, an increasing number of southerners express concern that northerners will overwhelm them.

In particular, they resent the imposition of Arabic as the official language of administration, which deprives most of the few educated English-speaking southerners of the opportunity to enter public service.

They also feel threatened by the replacement of trusted British district commissioners with unsympathetic northerners.

After the government replaces several hundred colonial officials with Sudanese, only four of whom are southerners, the southern elite abandons hope of a peaceful, unified, independent Sudan.

The hostility of Sudan's southerners toward the northern Arab majority surfaces violently when southern army units mutiny in August 1955 to protest their transfer to garrisons under northern officers.

The rebellious troops kill several hundred northerners, including government officials, army officers, and merchants

The government quickly suppresses the revolt and eventually executes seventy southerners for sedition, but this harsh reaction fails to pacify the south, as some of the mutineers escape  to remote areas and organize resistance to the Arab-dominated government of Sudan.

In particular, they resent the imposition of Arabic as the official language of administration, which deprives most of the few educated English-speaking southerners of the opportunity to enter public service.

They also feel threatened by the replacement of trusted British district commissioners with unsympathetic northerners.

After the government replaces several hundred colonial officials with Sudanese, only four of whom are southerners, the southern elite abandons hope of a peaceful, unified, independent Sudan.

The Sudanese electorate gives a plurality in both houses to the Umma and an overall majority to the Umma-PDP coalition.

The NUP, however, wins nearly one-quarter of the seats, largely from urban centers and from Gezira Scheme agricultural workers.

In the Sudanese south, the vote represents a rejection of the men who had cooperated with the government—voters defeat all three southerners in the preelection cabinet—and a victory for advocates of autonomy within a federal system.

Resentment against the government's taking over mission schools and against the measures used in suppressing the 1955 mutiny contributes to the election of several candidates who had been implicated in the rebellion.

Southern Sudanese leaders had in 1963 renewed the armed struggle against the Sudanese government that had continued sporadically since 1955.

The rebellion has been spearheaded from 1963 by guerrilla forces known as the Anyanya (the name of a poisonous concoction).