History of Sudan
The modern Republic of Sudan was formed in 1956 and inherited its boundaries from Anglo-Egyptian Sudan, established in 1899. For times predating 1899, usage of the term "Sudan" for the territory of the Republic of Sudan was somewhat anachronistic, and may have referred to the more diffuse concept of the Sudan.
South Sudan
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.