Why did Islam become the undoubted ruler of the Mediterranean?
Have you ever thought how the Arabs, a nomadic people, managed to rule the Mediterranean and beyond? How did they expand beyond their small (by comparison) region in the Middle East and occupied areas such as North Africa, Spain and the Eastern Mediterranean?
Most scholars agree that one of the main factors that allowed the Arabic conquests was the tendencies towards their political unification and centralization of power. Allah, the one and only God to whom they believed, in a way made this unification possible. It also gave them the impetus to spread the divine word to other areas and thus make their religion universal. Islam itself preached a message of social and political unification and, thus, united the Arabs. Through prayer and religious fervour the new Arabic nation knew no boundaries, by divine intervention. Islam doctrine affected deeply the political decisions of the rulers, provided guidance and gave them greater political and social authority.
Religious beliefs obviously played an important role in securing the loyalty of the individuals to the new unifying state. There have been, though, also other means to give incentive to the Arabs to remain firmly loyal. One of the most powerful ones was booty that followed looting during wars. Military expeditions in the past were an excellent way to pay for the expenses of the armies. In many cases, military leaders would pay for the wages of the soldiers until after the battle, thus ensuring their participation. Booty was an added bonus that ensured the loyalty of the troops.
In addition, the organization of a centrally controlled army united the Arabs and weakened their tribal links. Tribesmen started feeling that they belonged to the central state. Lines of command cut across different tribes and overcame the older tribal identities. The prophet, Muhammad, placed great emphasis on the importance of settlement (hijra) and the abandonment of the nomadic life. Although the identities of being and nomad and being a Muslim were not in conflict, one seemed to be more powerful than the other.
In order to reduce the power of the tribes the reigning elite recruited nomads into the centralised army. In order to ensure the loyalty of these tribesmen to a central Muslim cause, they transported them away from their desert homes into garrison towns. Consequently, on one hand the political and military power of the tribes was reduced, while the Islamic state became even more powerful. At the same time, the Arabic rulers made certain that very few men of fighting age were left back in their homes; this way they ensured that there would be no pockets of resistance to their decisions.
Apart from the internal factors that led to the rise of Islam, there have been also external factors. By the time of the Prophet, the Byzantine empire and its counterpart, the Sassanian empire, have already lost their political strength and military prowess. Both empires were facing internal political strife and insecurities when it came to the inheritance of the throne. At the same time, opposing religious factions eroded religious unification and caused widespread riots (or even wars) over several centuries. These problems were a distinct advantage for the united and powerful Islam. As if these problems were not enough, the weather has also conspired against the Sassanians. Immense floods in southern Iraq became responsible for material destructions on a very large economic scale.
On the whole, the rise of Islam was the result of a combination of internal and external factors. The attempts to centralise the Arabic State, the creation of a new Arabic identity based on religious doctrine, and the timely deterioration of the political power of the Sassanians and the Byzantines were fundamental causes.
I suppose its a case of what came first – the empire or the religion. To me, I think the Arab empire arose in a similar way to all previous empires and that religion/dogma followed later. A sort of backfilling to justify the existence of that empire?