treaty, gives two different versions of the treaty. The first has only Nubia sending slaves north, thus symbolizing its subservience to Egypt. The second version adds an obligation of the Egyptians to also send goods south including wheat and lentils in exchange for the slaves; this would put the two nations on a more equal footing. The second version is more reliable as it conforms with the Nubian version of treaty and further conforms with the results of the first and second Battles of Dongola. Context and consequences This treaty was unprecedented in the history of the Arab conquests, being more similar to the arrangements the Eastern Roman Empire sometimes made with its neighbours. It is also unmatched in that it largely blocked the spread of Islam and the Arabs for half a millennium. Spaulding reports that the exchange of goods was a common diplomatic arrangement in Northeast Africa and the Nubians would have had long experience with such agreements. The Baqt caused some controversy among Islamic theologians as there was disagreement over whether it violated the duty to expand the borders of Islam. History of Enforcement The Baqt was not always without controversy and conflicts between the neighbours were not unheard of. Abbasid period In the 830s, Egypt plunged into turmoil during the Fourth Fitna and King Zacharias III of Makuria halted payment of the Baqt. When the Abbasid government gained firm control of Egypt, the Abbasids demanded resumption of the Baqt and payment of arrears. Unable or unwilling to pay this large sum Zacharias sent his son and heir Georgios on a long journey to Baghdad in 835 to negotiate directly with the Caliph. This expedition was a great success; the arrears were canceled and the Baqt was altered so that it only had to be paid every three years. Fatimid period The closest relations were during the Fatimid period in Egypt. The Shi'ite Fatimids had few allies in the predominantly Sunni Islamic world, and Nubia was an important ally. The slaves sent from Nubia made up the backbone of the Fatimid army. Ayyubid and Mamluk periods Relations were worse under the Ayyubids and very poor under the Mamluks, with full-scale war eventually breaking out. Even after Makuria collapsed in the thirteenth century, the Egyptians continued to insist upon its payment by the Muslim successor kingdoms in the region. The Baqt finally ended in the mid-fourteenth century with