The murder of Severus Alexander by his soldiers and its aftermath which resulted in disturbances in Rome, motivated Ardashir to attack Rome again. In about the years 237–238, Ardashir took Nusaybin and Harran and attacked the city Dura; then he marched toward Hatra, which was a commercial city and the center of the traffic of commercial caravans. Hatra stood hard against the Persian siege and did not fall until April or September 240; it seems that Hatra was chosen as a point for pushing and operation against Roman Mesopotamia. The fall of Hatra might have been the cause of Gordian III's wars with Persia.