origin. After a period of withdrawal, the Middle Kingdom of Egypt conquered Lower Nubia from 2000 to 1700 BC. By 1900 BC, King Sesostris I began building a series of towns below the Second Cataract with heavy fortresses that had enclosures and drawbridges. Sesotris III relentlessly expanded his kingdom into Nubia (from 1866 to 1863 BC) and erected massive river forts including Buhen, Semna, Shalfak and Toshka at Uronarti to gain more control over the trade routes in Lower Nubia. They also provided direct access to trade with Upper Nubia, which was independent and increasingly powerful during this time. These Egyptian garrisons seemed to peacefully coexist with the local Nubian people, though they did not interact much with them. Medjay was the name given by ancient Egypt to nomadic desert dwellers from east of the Nile river. The term was used variously to describe a location, the Medjay people, or their role/job in the kingdom. They became part of the Egyptian military as scouts and minor workers before being incorporated into the Egyptian army. In the army, the Medjay served as garrison troops in Egyptian fortifications in Nubia and patrolled the deserts as a kind of gendarmerie, or elite paramilitary police force, to prevent their fellow Medjay tribespeople from further attacking Egyptian assets in the region. The Medjay were often used to protect valuable areas, especially royal and religious complexes. Although they are most notable for their protection of the royal palaces and tombs in Thebes and the surrounding areas, the Medjay were deployed throughout Upper and Lower Egypt; they were even used during Kamose's campaign against the Hyksos and became instrumental in turning the Egyptian state into a military power. After the First Intermediate Period of Egypt, the Medjay district was no longer mentioned in written records. Kerma; Egyptian Empire (1550–750 BC) Upper Nubia From the Middle Kerma phase, the first Nubian kingdom to unify much of the region arose. The Classic Kerma culture, named for its royal capital at Kerma, was one of the earliest urban centers in the Nile region and oldest city in Africa outside of Egypt. The Kerma group spoke either languages of the Cushitic branch or, according to more recent research, Nilo-Saharan languages of the Eastern Sudanic branch. By 1650 BC (Classic Kerma phase), the kings of Kerma were powerful enough to organize the labor for monumental town walls and large mud brick structures,