By the 6th century, fifty states had emerged as the political and cultural heirs of the Meroitic Kingdom. Nobatia in the north, also known as Ballanah, had its capital at Faras, in what is now Egypt; the central kingdom, Muqurra (Makuria), was centred at Dunqulah, about 13 kilometres (10 miles) south of modern Dunqulah; and Alawa (Alodia), in the heartland of old Meroe, which had its capital at Sawba (now a suburb of modern-day Khartoum). In all three kingdoms, warrior aristocracies ruled Meroitic populations from royal courts where functionaries bore Greek titles in emulation of the Byzantine court. A missionary sent by Byzantine empressTheodora arrived in Nobatia and started preaching Christianity about 540 AD. The Nubian kings becameMonophysite Christians. However, Makuria was of the Melkite Christian faith, unlike Nobatia and Alodia.
After many attempts at military conquest failed, the Arab commander in Egypt concluded the first in a series of regularly renewed treaties known asAlbaqut al-sharim (pactum) with the Nubians that governed relations between the two peoples for more than 678 years. Islam progressed in the area over a long period of time through intermarriage and contacts with Arab merchants and settlers, particularly the Sufi nobles of Arabia. Additionally, exemption from taxation in regions under Muslim rule were also a powerful incentive for conversion. In 1093, a Muslim prince of Nubian royal blood ascended the throne of Dunqulah as king. The two most important Arab tribes to emerge in Nubia were the Jaali and the Juhayna. Today’s northern Sudanese culture often combines Nubian and Arabic elements.
During the 16th century, a people called the Funj, under a leader named Amara Dunqus, appeared in southern Nubia and supplanted the remnants of the old Christian kingdom of Alwa, establishing As-Saltana az-Zarqa (the Blue Sultanate), also called the Sultanate of Sennar. The Blue Sultanate eventually became the keystone of the Funj Empire. By the mid-16th century, Sennar controlled Al Jazirah and commanded the allegiance of vassal states and tribal districts north to the Third Cataract and south to the rainforests. The government was substantially weakened by a series of succession arguments and coups within the royal family. In 1820, Muhammad Ali of Egypt sent 4,000 troops to invade Sudan. His forces accepted Sennar’s surrender from the last Funj sultan, Badi VII.
Info from https://en.wikipedia.org/wiki/Sudan