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.
Juba Conference (1947)
This disparity lead to the First and Second Sudanese Civil Wars, eventually resulting, in 2011, in the Southern provinces becoming an independent state, the Republic of South Sudan.