As the Roman Empire expanded further eastward, annexing territories that were once the domain of the Parthians, the legions of Mesopotamia, Cappadocia, and Arabia were called upon to safeguard these newly acquired territories. Mesopotamia had two permanent legions, I Parthica and III Parthica, Cappadocia was the home base of XII Fulminata and XV Apollinaris, while III Cyrenaica was stationed in Arabia.
This is a companion discussion topic for the original content at https://www.worldhistory.org/article/1988/legions-of-mesopotamia-cappadocia--arabia/.