Throughout the post-classical era, several religions rose to prominence - and Islam stands out as the fastest growing religion during this time. In a few centuries, the originally Arab-centered religion grew to cover the expanses of western, eastern, and northern Africa, as well as huge territories in Eurasia. There are many explanations on how Islam was able to spread so quickly, but all must agree that for this growth to occur, the conditions of the world at the time had to be perfect. Everything was in such a condition so as to allow Islam to expand over continents. From its humble beginnings in the middle of Arabia, the Islamic religion began a ceaseless and rapid growth across Afro-Eurasia largely in part to the powerful Muslim armies and rulers, the simple Koranic messages of equality which trumped the local beliefs, and the ability of Muslim traders to spread out from the Islamic empire and spread the ideas of Islam around the world.
The early foundations of the Islamic empire were sown by powerful armies that brought everyone under the rule of a unified Islamic government. Once the Bedouin tribes of Arabia had been unified, their skills as fighters were used by the caliphate in order to gain more territory. These armies successfully drove through Northern and Eastern Africa, establishing territories of the caliphate as they went. The army also turned north and conquered most of the Persian Empire. This original rapid expansion took only a century, and allowed the Islamic empire to establish itself as a power on the world stage. The success of the military was largely in part to the weakness of surrounding empires such as the Byzantium Empire and the Persian Empire. In the case of Egypt, there was already an existing loathing of their Byzantine conquerors who governed from far away. This resentment allowed the territory to be easily turned over to Islamic hands. The initial ability of Islam to muster large armies and conquer vast expanses across Afro-Eurasia formed the base of the mighty empire, but once out of the hands of the army, it was the job of the caliph to supervise these areas.