Islam expansionTo what degree of the beliefs of islam, distinct from other aspects of Arab culture between 600 and 50 C.E, appear to have motivated Muslims to expand the territory under their...
In response to other questions you've asked, I've tried to call attention to the value of Google Books and Google Scholar. Rather than repeating myself here, I'll simply run searches in both places concerning the question you raise here. Here are the results of those searches:
I hope these links are helpful to you!
I would say that it was a relatively small degree. Islam taught that all people should accept Islam and that therefore it was important to spread out and expose more people (whether voluntarily or not) to the faith.
It is hard to say, though, that Arabs would not have been motivated to expand had it not been for Islam. It seems that all strong peoples try to expand at some point.
So, I would argue that Islam helped to unify the Arabs and make it possible for them to expand. But it is hard to argue that a unified Arab people would not have wanted to expand if they had not been Muslim.
To expand on #2, it could be argued that without the original unifying force of Muhammed, the disparate Arab tribes would not have unified for many years. With the power of a religious standard, a solid and concrete faith to cling to beyond tradition, the tribes were better able to form larger governmental structure, laws, and culture. With Muhammed's death, the inevitable conflict over interpretation arose, and factions that could not live with the centralized believers spread out to find their own regions.
Any of the major religions is explicitly evangelistic in the sense of wanting to convert and persuade others to follow their creeds and beliefs. I am not too sure if your question relates to the explicit missionary strand that is part of Islam or whether you are relating this to political control, but it is clear that a key responsibility of Muslims is to share their faith and to try and convert others.
Religion often leads empires to expand. Most religions want their members to collect converts. The quickest way to do so is by expanding and conquering. By conquering other regions, you can force them to convert or convert them to your religion.