After Muhammad's death, the expansion of Islam began and the unification of Arab tribes, by forming caliphates headed by religious leaders, caliphs, which began the spread of the Islamic territory. This also meant acquiring territories that were not completely Arabian. It should be kept in mind that Persia, the successor to the ancient Mesopotamia, and as such, largely contained the territory of ancient Mesopotamia, although not all. Thus, 25 years after Muhammad's death, the territories acquired included parts of Persia, Mesopotamia and Egypt.
