So let’s say that Alexander either never exists or never conquers the Achaemenid Empire. Maybe he dies at the Granicus River, or gets hit by a stray sling bullet at Gaza. Either way, the Achaemenid Empire survives intact. However, the Achaemenids had to deal with jealous satraps, disloyal subject peoples, a decreasing supply of gold, and troubles in the court. Without Alexander to bring the whole thing crashing down, how would the collapse of the Achaemenids play out? How much longer can it survive without Alexander? And what would happen after the Achaemenids fall?