South Sudan, which was the southern part of Sudan until 2011, has a history of friction with the regions to its north; the conflict in large part has been a result of religious differences with the Muslim-dominated north. Egypt, which had conquered Sudan earlier in the 1800s, began to colonize South Sudan in the 1860s. In the 1880s the region fell to the Mahdist uprising (see Madhi), but in both cases actual control over South Sudan was limited. The British established control after finally defeating the Mahdists in 1898, and the area became part of the Anglo-Egyptian Sudan. In 1924 the British separated the administration of N and S Sudan. The Juba Conference (1947) led to the rejoining of the two regions.
With the advent of independence in the mid-1950s, southerners, fearing domination by the Muslim north, started a revolt that lasted 17 years; the civil war left some 1.5 million southern Sudanese dead as a result of fighting, starvation, and disease. The rebellion was ended by an agreement between the government and the Southern-Sudan Liberation Front (whose military arm was known as Anya Nya) signed in 1972 at Addis Ababa, Ethiopia; under the accord the S Sudan received considerable autonomy.
A second civil war was begun in 1983 by the Sudan People's Liberation Army (SPLA), led by John Garang, when the Sudanese government revoked the 1972 agreement and then imposed Islamic law. In the 1990s the Sudanese army mounted offensives against the SPLA in S Sudan; several cease-fires were announced to allow the distribution of food to famine victims, but they did not hold. The Sudanese government and Sudan People's Liberation Movement (SPLM, the SPLA's political arm) agreed in July, 2002, to a framework for peace that called for autonomy for the south and a referendum on independence after six years; a truce was signed in October, and talks led to a peace agreement in 2005. Some 2 million people died during the second conflict, mostly from disease and starvation.
When S Sudan became autonomous in 2005, Garang became president of S Sudan and first vice president of Sudan; oil revenues from southern wells were split between the north and south. Garang died in July, 2005, and was succeeded in both his posts by the SPLM's Salva Kiir. Tensions continued between south and north, with occasional outbreaks of violence (especially in the disputed oil-rich border region of Abyei). There also was fighting between the SPLA and other southern militia groups, which in some cases continued after independence. Kiir was overwhelmingly reelected in Apr., 2010, but the election was marked by significant problems. In Jan., 2011, a referendum on the future of S Sudan resulted more than 98% of the population of the region voting for independence. The country was declared a separate republic on July 9, 2011, and Kiir became South Sudan's first president.
Abyei, inhabited mainly by Dinkas and Arabs, remains disputed between South Sudan and Sudan; it did not participate in the 2011 referendum, and in May, 2011, Sudanese government forces seized control of the region. Relations with Sudan have been difficult. There have been a number of disputes concerning the shipment of South Sudanese oil through Sudanese pipeline and port facilities; as a result, South Sudan shut down oil production in early 2012, which drastically reduced the nation's revenues.
Fighting between the Sudanese government and former allies of the SPLA has led to cross-border attacks at times by Sudanese and South Sudanese forces, with more significant border clashes in March and April of 2012 that also involved territory disputed between the two nations. The March–April fighting led to an AU-UN ultimatum that demanded an end to fighting and a resolution of the border issues. An agreement on restoring oil production and shipment and other issues was signed in September, but border issues and the status of Abyei remained unresolved and delayed implementation of the agreement. Despite the fitful progress toward implementation of the agreement, South Sudan resumed oil production in Apr., 2013. Both South Sudan and Sudan have been accused of arming each other's rebels.
In 2011–13 there were significant ethnically based cattle raids and deadly revenge attacks in E South Sudan. Also in 2012, South Sudanese troops were included in a planned four-nation African Union force led by Uganda to capture Ugandan rebel leader Joseph Kony. Kiir dismissed (July, 2013) Vice President Riek Machar and the cabinet in a shakeup designed to remove his political rivals from the government. In Dec., 2013, Kiir accused Machar of an attempted coup, and the situation quickly deteriorated into a murderous civil war, largely along ethnic lines, with Dinka supporting Kiir and Nuer backing Machar. Nuer forces captured an number of state capitals, but Kiir forces, with support at times from Uganda, regained control of those cities in Jan., 2014. Corruption is a significant problem in the young nation's government.