It was the expanding power of Abyssinia that led Rome to call in the Nubians from the western desert.  The Nubians had formed a strong league of tribes, and as the ancient kingdom of Ethiopia declined they drove back the Abyssinians, who had already established themselves at Meroe.

In the sixth century the Nubians were converted to Christianity by a Byzantine priest, and they immediately began to develop.  A new capital, Dongola, replaced Nepata and Meroe, and by the twelfth century churches and brick dwellings had appeared.  As the Mohammedan flood pressed up the Nile valley it was the Nubians that held it back for two centuries.

Farther south other wild tribes pushed out of the Sudan and began a similar development.  Chief among these were the Fung, who fixed their capital at Senaar, at the junction of the White and Blue Nile.  When the Mohammedan flood finally passed over Nubia, the Fung diverted it by declaring themselves Moslems.  This left the Fung as the dominant power in the fifteenth century from the Three Cataracts to Fazogli and from the Red Sea at Suakin to the White Nile.  Islam then swept on south in a great circle, skirted the Great Lakes, and then curled back to Somaliland, completely isolating Abyssinia.

Between the thirteenth and sixteenth centuries the Egyptian Sudan became a congeries of Mohammedan kingdoms with Arab, mulatto, and Negro kings.  Far to the west, near Lake Chad, arose in 1520 the sultanate of Baghirmi, which reached its highest power in the seventh century.  This dynasty was overthrown by the Negroid Mabas, who established Wadai to the eastward about 1640.  South of Wadai lay the heathen and cannibals of the Congo valley, against which Islam never prevailed.  East of Wadai and nearer the Nile lay the kindred state of Darfur, a Nubian nation whose sultans reigned over two hundred years and which reached great prosperity in the early seventeenth century under Soliman Solon.

Before the Mohammedan power reached Abyssinia the Portuguese pioneers had entered the country from the east and begun to open the country again to European knowledge.  Without doubt, in the centuries of silence, a civilization of some height had flourished in Abyssinia, but all authentic records were destroyed by fire in the tenth century.  When the Portuguese came, the older Axumite kingdom had fallen and had been succeeded by a number of petty states.

The Sudanese kingdoms of the Sudan resisted the power of the Mameluke beys in Egypt, and later the power of the Turks until the nineteenth century, when the Sudan was made nominally a part of Egypt.  Continuous upheaval, war, and conquest had by this time done their work, and little of ancient Ethiopian culture survived except the slave trade.