This instruction from the Qur'an stands for the challenge of the faith to the order of state and society established in the Arab empire by the end of the ninth century. Over the next three hundred years Islam became the first worldwide civilisation, stretching beyond the borders of the Arab empire to Tropical Africa and the Far East at the height of the prosperity of Lombard's Golden Age of Islam. Politically, however, the tenth, eleventh and twelfth centuries were years of revolution, which saw the break-up of the Arab empire and the failure of successive attempts to reconstitute it. Both the break-up and the failures turned on the impossibility of keeping control of such a vast domain, as the Muslim population turned from a foreign minority into a native majority in all its provinces. But the attempts themselves were ideologically driven, and turned on the call of Islam to tribal peoples on the fringe of the community, ungoverned by the state but responsive to the faith. In Africa, successive uprisings, invasions and conquests by these peoples not only determined the history of North Africa and Egypt. In combination with the growth of trans-Saharan trade, they completed the transformation of the desert from a margin of the lands to the north and south into an active centre of the continent.