Omar

After the prophet Mohammed died, the first caliph, Abu Bakr, was elected, in whose reign Muslims were able to unite the many tribes of Arabia. Omar followed, and during his time Muslims launched their conquest out of Arabia on the two main civilizations of that ancient world, the mighty Persian civilization in the East, with which battles took place in what is now Iraq, and the Roman civilization, with which battles took place in the Levant and North Africa, including Egypt. The scale of this simultaneous conquest was unprecedented.