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.
Ethnic federalism
South Sudan became independent of Sudan in July 2011, and initially the transitional constitution established 10 federal states and 79 counties, mostly based on ethnicity. Inter-communal conflict mounted, and there were calls from various groups for creation of further ethnocentric states and counties. Stephen Par Kuol, then minister of education in Jonglei state, opined in 2013 that "ethnic federalism" in his country had proved "divisive" and "expensive to run" and did not make for real democracy, and called for multi-ethnic states and counties to be created at least around the main cities.