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.
Arabization
Sudan is an ethnically-mixed country that is economically and politically dominated by the society of central northern Sudan, where many strongly identify as Arabs and Muslims. The population in southern Sudan consists mostly of Christian and Animist Nilotic people. The Second Sudanese Civil War (1983–2005) is typically characterized as a conflict between these two groups of people. In the 2011 Southern Sudanese independence referendum, the latter voted for secession and became independent.