Touraj Daryaee. The Political History of Ērān in the Sasanian Period

The Sasanika Project, Late Antique Near East Project, pp - 36
Ardaxšīr I was able to defeat Ardawān (Artabanus IV) at the plain of Hormozgān in 224 CE and established the Sasanian Empire. From then on Ardaxšīr took the title of šāhān šāh King of Kings and began the conquest of a territory which he called Ērān.