<P> Darius III was taken prisoner by Bessus, his Bactrian satrap and kinsman . As Alexander approached, Bessus had his men murder Darius III and then declared himself Darius' successor, as Artaxerxes V, before retreating into Central Asia leaving Darius' body in the road to delay Alexander, who brought it to Persepolis for an honorable funeral . Bessus would then create a coalition of his forces, in order to create an army to defend against Alexander . Before Bessus could fully unite with his confederates at the eastern part of the empire, Alexander, fearing the danger of Bessus gaining control, found him, put him on trial in a Persian court under his control, and ordered his execution in a "cruel and barbarous manner". </P> <P> Alexander generally kept the original Achaemenid administrative structure, leading some scholars to dub him as "the last of the Achaemenids" Upon Alexander's death in 323 BC, his empire was divided among his generals, the Diadochi, resulting in a number of smaller states . The largest of these, which held sway over the Iranian plateau, was Seleucid Empire, ruled by Alexander's general Seleucus I Nicator . Native Iranian rule would be restored by the Parthians of northeastern Iran over the course of the 2nd century BC . </P> <P> Istakhr, one of the vassal kingdoms of the Parthian Empire, would be overthrown by Papak, a priest of the temple there . Papak's son, Ardašir I, who named himself in remembrance of Artaxerxes II, would revolt against the Parthians, eventually defeating them and establishing the Sassanid Empire or as it is known the second Persian Empire . </P> <P> The Achaemenid line would be carried on through the Kingdom of Pontus, based in the Pontus region of northern Asia Minor . This Pontic Kingdom, a state of Persian origin, may even have been directly related to Darius the Great and the Achaemenid dynasty . It was founded by Mithridates I in 281 BC and lasted until its conquest by the Roman Republic in 63 BC . The kingdom grew to its largest extent under Mithridates VI the Great, who conquered Colchis, Cappadocia, Bithynia, the Greek colonies of the Tauric Chersonesos and for a brief time the Roman province of Asia . Thus, this Persian dynasty managed to survive and prosper in the Hellenistic world while the main Persian Empire had fallen . </P>

How did persian rulers maintain a large empire