The Nilotic people of South Sudan—the Acholi, Anyuak, Bari, Dinka, Nuer, Shilluk, Kaligi (Arabic Feroghe), and others—first entered South Sudan sometime before the 10th century coinciding with the fall of medieval nubia. During the period from the 15th to the 19th centuries, tribal migrations, largely from the area of Bahr el Ghazal, brought the Anyuak, Dinka, Nuer and Shilluk to their modern locations of both Bahr El Ghazal and Upper Nile Regions, while the Acholi and Bari settled in Equatoria. The Azande, Mundu, Avukaya and Baka, who entered South Sudan in the 16th century, established the region's largest state of Equatoria Region.
The Dinka are the largest, Nuer the second largest, the Azande the third-largest and the Bari are the fourth-largest ethnic group in the country. They are found in the 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. In the 18th century, the Avungara sib rose to power over the rest of Azande society and this domination continued into the 20th century. Geographical barriers, including the swamplands along the White Nile and the British preference for sending Christian missionaries to the southern regions, including its Closed District Ordinance of 1922 (see History of Anglo-Egyptian Sudan), helped to prevent the spread of Islam to the southerners, thus enabling them to retain their social and cultural heritage, as well as their political and religious institutions. The major reasons include the long history of British policy preference toward developing the Arab north and its ignoring the Black south. After Sudan's first independent elections in 1958, the continued ignoring of the south by Khartoum (lack of schools, roads, bridges) led to uprisings, revolt, and the longest civil war on the continent. As of 2012 , peoples include Acholi, Anyuak, Azande, Baka, Balanda Bviri, Bari, Boya, Didinga, Dinka, Jiye, Kaligi, Kuku, Lotuka, Mundari, Murie, Nilotic, Nuer, Shilluk, Toposa and Zande.
Slavery had been an institution of Sudanese life throughout history. The slave trade in the south intensified in the 19th century, and continued after the British had suppressed slavery in much of sub-Saharan Africa. Annual Sudanese slave raids into non-Muslim territories resulted 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 18th century. In the 19th century, the Azande fought the French, the Belgians and the Mahdists to maintain their independence. Egypt, under the rule of Khedive Ismail Pasha, first attempted to control the region in the 1870s, establishing the province of Equatoria in the southern portion. Egypt's first governor was Samuel Baker, commissioned in 1869, followed by Charles George Gordon in 1874 and by Emin Pasha in 1878.
The Mahdist Revolt of the 1880s destabilized the nascent province, and Equatoria ceased to exist as an Egyptian outpost in 1889. Important settlements in Equatoria included Lado, Gondokoro, Dufile and Wadelai. European colonial maneuverings in the region came to a head in 1898, when the Fashoda Incident occurred at present-day Kodok; Britain and France almost went to war over the region. In 1947, British hopes to join South Sudan with Uganda, as well as leaving Western Equatoria as part of the Democratic Republic of the Congo, were dashed by the Rajaf Conference to unify North and South Sudan.
South Sudan has an estimated population of 8 million, but, given the lack of a census in several decades, this estimate may be severely distorted. The economy is predominantly rural and relies chiefly on subsistence farming. Around 2005, the economy began a transition from this rural dominance, and urban areas within South Sudan have seen extensive development.
The region has been negatively affected by two civil wars since Sudanese independence: from 1955 to 1972, the Sudanese government fought the Anyanya rebel army (Anya-Nya is a term in the Madi language which means "snake venom") during the First Sudanese Civil War, followed by the Sudan People's Liberation Army/Movement (SPLA/M) in the Second Sudanese Civil War for over 20 years. As a result, the country suffered serious neglect, a lack of infrastructural development, and major destruction and displacement. More than 2.5 million people have been killed and millions more have become refugees both within and outside the country.
A South Sudanese girl at independence festivities
Between 9 and 15 January 2011, a referendum was held to determine whether South Sudan should become an independent country and separate from Sudan. 98.83% of the population voted for independence. South Sudan formally became independent from Sudan on 9 July, although certain disputes still remained, including the division of oil revenues, as 75% of all the former Sudan's oil reserves are in South Sudan. The region of Abyei still remains disputed and a separate referendum will be held in Abyei on whether they want to join Sudan or South Sudan. The South Kordofan conflict broke out in June 2011 between the Army of Sudan and the SPLA over the Nuba Mountains.
On 9 July 2011 South Sudan became the 54th independent country in Africa and since 14 July 2011, South Sudan is the 193rd member of the United Nations. On 27 July 2011 South Sudan became the 54th country to join the African Union.
South Sudan was at war with at least seven armed groups in 9 of its 10 states, with tens of thousands displaced. The fighters accuse the government of plotting to stay in power indefinitely, not fairly representing and supporting all tribal groups while neglecting development in rural areas. Joseph Kony's Lord's Resistance Army (LRA) also operates in a wide area that includes South Sudan.
Inter-ethnic warfare that in some cases predates the war of independence is widespread. In December 2011, tribal clashes in Jonglei intensified between the Nuer White Army of the Lou Nuer and the Murle. The White Army warned it would wipe out the Murle and would also fight South Sudanese and UN forces sent to the area around Pibor.
In March 2012, South Sudanese forces seized the Heglig oil fields in lands claimed by both Sudan and South Sudan in the province of South Kordofan after conflict with Sudanese forces in the South Sudanese state of Unity. South Sudan withdrew on 20 March, and the Sudanese Army entered Heglig two days later.
Civil war (2013–present)
Military situation in South Sudan as of 1 April 2016
Under control of the Government of South Sudan
In December 2013, a political power struggle broke out between President Kiir and his former deputy Riek Machar, as the president accused Machar and ten others of attempting a coup d'état. Fighting broke out, igniting the South Sudanese Civil War. Ugandan troops were deployed to fight alongside South Sudanese government forces against the rebels. The United Nations has peacekeepers in the country as part of the United Nations Mission in South Sudan (UNMISS). Numerous ceasefires were mediated by the Intergovernmental Authority on Development (IGAD) between the Sudan People's Liberation Movement (SPLM) and SPLM – in opposition and were subsequently broken. A peace agreement was signed in Ethiopia under threat of United Nations sanctions for both sides in August 2015. Machar returned to Juba in 2016 and was appointed vice president. Following a second breakout of violence in Juba, Machar was replaced as vice-president and he fled the country as the conflict erupted again. Rebel in-fighting has become a major part of the conflict. Rivalry among Dinka factions led by the President and Malong Awan have also led to fighting. In August 2018, another power sharing agreement came into effect.
About 400,000 people are estimated to have been killed in the war, including notable atrocities such as the 2014 Bentiu massacre. Although both men have supporters from across South Sudan's ethnic divides, subsequent fighting has been communal, with rebels targeting members of Kiir's Dinka ethnic group and government soldiers attacking Nuers. More than 4 million people have been displaced, with about 1.8 million of those internally displaced, and about 2.5 million having fled to neighboring countries, especially Uganda and Sudan.