Synopsis: King Artabanus of Parthia gathers his forces to seek revenge on Rome. Usurpation and war gain the Sasanids control over the southern territory of Fars.
“Macrinus, seeing that Artabanus was exceedingly angry at the way he had been treated and had invaded Mesopotamia with a large force, at first of his own accord sent him captives and used friendly language, urging him to accept peace and laying the blame for the past on (Caracalla). But the other would not entertain his proposition, and furthermore bade him build up the forts and demolished cities, abandon Mesopotamia entirely and offer satisfaction in general, but particularly for the damage to the royal tombs. For, trusting in the large force that he had gathered, and despising Macrinus as an unworthy emperor, he gave reign to his wrath and expected that even without Roman consent he could accomplish whatever he wished.” – Cassius Dio, Rome, Book 78
Map of the Parthian Empire