period of nearly one thousand years. Arab nomads continually wandered into the region in search of fresh pasturage, and Arab seafarers and merchants traded at Red Sea ports for spices and slaves. Intermarriage and assimilation also facilitated Arabization. After the initial attempts at military conquest failed, the Arab commander in Egypt, Abd Allah ibn Saad, concluded the first in a series of regularly renewed treaties with the Nubians that governed relations between the two peoples for more than six hundred years with only brief interruptions. This treaty was known as the Treaty of Baqt. So long as Arabs ruled Egypt, there was peace on the Nubian frontier; however, when non-Arabs, the Mamluks for example, acquired control of Egypt, tension arose in Nubia. The Arabs realized the commercial advantages of peaceful relations with Nubia and used the Baqt to ensure that travel and trade proceeded unhindered across the frontier. The Baqt also contained security arrangements whereby both parties agreed that neither would come to the defense of the other in the event of an attack by a third party. The Baqt obliged both to exchange annual tribute as a goodwill symbol: the Nubians sent slaves and the Arabs sent grain. This formality was only a token of the trade that developed between the two. It was not only a trade in slaves and grain but also in horses and manufactured goods brought to Nubia by the Arabs, and in ivory, gold, gems, gum arabic, and cattle carried back by them to Egypt, or shipped to Arabia. Acceptance of the Baqt did not indicate Nubian submission to the Arabs; however, the treaty did impose conditions for Arab friendship that eventually permitted Arabs to achieve a privileged position in Nubia. Arab merchants established markets in Nubian towns to facilitate the exchange of grain and slaves. Arab engineers supervised the operation of mines east of the Nile in which they used slave labor to extract gold and emeralds. Muslim pilgrims en route to Mecca traveled across the Red Sea on ferries from Aydhab and Suakin, ports that also received cargoes bound from India to Egypt. Traditional genealogies trace the ancestry of the Nile Valley's area of Sudan mixed population to Arab tribes that migrated into the region during this period. Even many non-Arabic-speaking groups claim descent from Arab forebears. The two most important Arabic-speaking groups to emerge in Nubia were the Ja'alin and the