During World War II, some British colonial officers questioned the economic and political viability of the southern provinces as separate from northern Sudan. Britain also had become more sensitive to Arab criticism of the southern policy. In 1946 the Sudan Administrative Conference determined that Sudan should be administered as one country. Moreover, the conference delegates agreed to readmit northern administrators to southern posts, abolish the trade restrictions imposed under the "closed door" ordinances, and allow southerners to seek employment in the north. Khartoum also nullified the prohibition against Muslim proselytizing in the south and introduced Arabic in the south as the official administration language.

Some southern British colonial officials 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 argued that northern domination of the south would result in a southern rebellion against the government. Khartoum 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 postindependence government would safeguard southern political and cultural rights.

Despite these promises, an increasing number of southerners expressed concern that northerners would overwhelm them. In particular, they resented the imposition of Arabic as the official language of administration, which deprived most of the few educated English-speaking southerners of the opportunity to enter public service. They also felt threatened by the replacement of trusted British district commissioners with unsympathetic northerners. After the government replaced several hundred colonial officials with Sudanese, only four of whom were southerners, the southern elite abandoned hope of a peaceful, unified, independent Sudan.

The hostility of southerners toward the northern Arab majority surfaced violently when southern army units mutinied in August 1955 to protest their transfer to garrisons under northern officers. The rebellious troops killed several hundred northerners, including government officials, army officers, and merchants. The government quickly suppressed the revolt and eventually executed seventy southerners for sedition. But this harsh reaction failed to pacify the south, as some of the mutineers escaped to remote areas and organized resistance to the Arab-dominated government of Sudan.

Data as of June 1991