[1] Caracalla's choice of contacting Vologases instead of Artabanus shows that the Romans still saw him as the dominant king.

He appointed a freedman named Theocritus as the leader of the invasion, which eventually ended in a disaster.

[1] Caracalla's choice to contact Artabanus shows that the latter was now considered the dominant king over Vologases, who would rule a small principality centered around Seleucia until 221/2.

A few years later (224), Ardashir I (r. 224–242), the founder of the Sasanian dynasty, defeated and killed Artabanus, thus putting an end to the Parthian Empire.

Over the next few years, Ardashir I further expanded his new empire, and must have driven out or defeated Vologases in Mesopotamia soon after 228.