Answer:
Middle East and Northern Africa
Explanation:
The Muslim expansion started off with the prophet Muhammad. After Muhammad managed to unite the Arab tribes into one big force, the military campaigns started.
The surrounding areas were all relatively ease to conquer, as there were empires that were very weakened and on the decline, be it because of internal problems, or because of big losses from the plague. This was used by the Muslims and they rapidly managed to gain control over a very large territory.
The two regions that they managed to take over entirely were the Middle East and Northern Africa, and this can be easily seen even in modern times. There were conquests in other areas as well, but they were either short lasting, or in very small parts of a general region.
The rest of the territory where the Islam spread out was mostly through the trade routes and through preaching of the religion, such as Central Asia, South Asia, and Indonesia.
