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.
Egypt–Sudan relations
Sudan and Egypt have enjoyed long-standing complex historical ties, centred on historical overlaps in antiquity when Nubian kingdoms (Nobatia, Makuria and Alodia) in Sudan controlled Egypt, and Egyptian dynasties invaded Sudan, as well as cultural ties and Egypt's quest for controlling the Nile's waters. Prior to Sudanese independence in 1956, Sudan was incorporated into Egypt in 1821 through the Muhammad Ali dynasty invasion and occupation of Sudan followed by the Mahdist Sudan national revolution in 1885 and the subsequent reconquest of Sudan under British rule in 1899.