Complex sentence: Emperor Caracalla elevated Palmyra into a Colonia between 213 and 216, but the Severan led Roman-Parthian war which lasted from 194 to 217 also played a part in Palmyra transition, as it influenced the regional security and affected the trade of the city.
Split into simpler sentences: Emperor Caracalla elevated Palmyra into a Colonia between 213 and 216. In addition to their favor, the Severan led Roman-Parthian war which lasted from 194 to 217 also played a part in Palmyra's transition, as it influenced the regional security and affected the trade of the city.