The region is mostly desert and mountainous, so any large scale military activity is unpractical, considering the logistical issue. This is one of the reasons why Egypt had such a large casualty rate in its 1960s military adventurism in Yemen, leading to over 30,000 Egyptian army deaths.
Harsh terrain, limited supplies, poor water availability, poor resources.
The Persian Empire , as a civilization power purposely evaded the desert states since it provided no natural resource or economic incentive. Rather, Persia conquered Assyria, Mesopotamia, Egypt, Bacteria, Greece, and Asia Minor , all of which were resource rich , population rich areas.
Interestingly enough, in the 12th century when the Mongol Empire invaded the Middle East , it conquered the capital of Baghdad, the seat of power of the Abbasid Caliphate. When the Khan was asked if he wanted to seize Arabia, he said "no" because of the poor terrain. There are no economic incentives.
I was raised Christian, but a new convert to Islam, my friend.
It took me 10 years, but i had been studying Islam for a very long, long , long time.