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.
Flag of South Sudan
From the outset, the southern Sudanese felt discriminated against by the Islamic north. The southerners fought a drawn out and bloody civil war to gain their independence, followed by a peace agreement in 2005 that included a referendum on independence in the south. The referendum was passed with overwhelming support in 2011, and South Sudan became officially independent on July 9 that same year. In the 1990s, during their struggle with the north, the southern Sudanese had created a banner of independence, which would become the new national flag.