[1] Since the end of the 3rd or the beginning of the 2nd century BCE, Pars has been ruled by local dynasties subject to the Hellenistic Seleucid Empire.

[2] These dynasts held the ancient Persian title of frataraka ("leader, governor, forerunner"), which is also attested in the Achaemenid-era.

[2] The frataraka were shortly afterwards replaced by the Kings of Persis, most likely at the accession of the Arsacid monarch Phraates II (r. 132–127 BC).

[5] A son of Dara II named Sasan (called "the elder") fled to India and lived there in exile until his death.

[5] According to the medieval Iranian historian Al-Tabari (d. 923), Pabag was the son of Sasan and a princess named Rambihisht, who was from the Bazrangid family, a dynasty of rulers in Pars.

According to the Roman historians Agathias and George Syncellus, Sasan was the biological father of Ardashir, while Pabag was his stepfather.

[7] A Greek variant of Agathangelos' work calls Ardashir "son of Sasanus, which is the origin of the Sasanian name of the Persian kings descended from him".

[7] Ardashir, in his coin engravings and inscription on Naqsh-e Rostam, claims to be the son of "divine Pabag, the king".

[8] The modern historian Marek Jan Olbrycht suggests that Sasan was an Indo-Parthian prince who married a Persian princess and gave birth to Ardashir.

[14] The Iranologist Touraj Daryaee argues that the reign of Vologases V was "the turning point in Arsacid history, in that the dynasty lost much of its prestige.

However, Daryaee considers this statement unlikely, and states that it was in reality the eldest son Shapur who helped Pabag capture Istakhr, as demonstrated by the latter's coinage, which has portraits of both of them.

[14][13] In an act of defiance, Ardashir left for Ardashir-Khwarrah, where he fortified himself, preparing to attack his brother Shapur after Pabag's death.