Before Alexander the Great died he had ordered Nearchus to prepare a fleet and army in preparation for the invasion of Arabia. However he died before the conquest can take place and the effort was called off. But, what if he lived just long enough for the attack to take place, while dying shortly afterwards? Would Arabia become a fourth Diadochi Successor state or just become part of the Seluecid Empire? And who will be the leader? Nearchus?
Any thoughts?
The main problem is Arabia had not belonged to the Achaemenid Empire. And Alexander the Great did not conquer such countries in OTL.
The pattern of his conquest was, his message was:
- 'before you were ruled by the Achaemenid shahinshah and the Persians, now I will be instead the shahinshah and the Macedonians will replace the Persians; everything else will stay the same'.
That is of course a simplification, but close.
But the Arabian entities had never been ruled by a foreign power, they had never been a part of any Empire.
And from what we know they were fiercely independent.
So the old pattern of Alexander won't work here, no way. These are different circumstances. Different pattern.
This is not about having new Macedonian overlords instead of previous Persian ones. That is about losing your freedom. And usually that's a long and painful process, with setbacks and rebellions.
So the most probable scenario is - the richest coastal parts of Arabia are conquered by Alexander the Great: some after fierce resistance and huge losses for the invaders and the invaded, some without fight horrified and overwhelmed by the Grand Army and the Grand Fleet.
They are properly taxed and the Macedonian/Greek garrisons are placed in the most strategically important places.
The moment Alexander the Great dies all Arabia is in revolt and most of the Macedonians/Greeks are massacred.
You know the diadochi fought against other diadochi mostly; meaning those who win get the territory; those were the rules of the game.
In Arabia it won't be that way, there you have to conquer the country anew. It's not worth the effort.
So the Arabian polities will get independent again.
The only way for Arabia to stay inside the Hellenistic World is heavy Hellenization of the peninsula by Alexander the Great, the Greeks settled there in huge quantities, making them more numerous than the locals.
But that's not too probable, because you know Arabia is rich and is favorably situated, but what makes it better than say Mesopotamia or Syria or any other prosperous part of the Empire?