Wars of the Diadochi
The Persian provinces in what is now modern Afghanistan, together with the wealthy kingdom of Gandhara and the states of the Indus Valley, had all submitted to Alexander the Great and become part of his empire. When Alexander died, the Wars of the Diadochi ("Successors") split his empire apart; as his generals fought for control of Alexander's empire. In the eastern territories one of these generals, Seleucus I Nicator, was taking control and was starting to establish what became known as the Seleucid Empire. According to the Roman historian Appian, Seleucus,