The Roman legions of Syria served as a buffer, protecting the Roman Empire not only externally from such threats as Parthia and the Sasanian Empire but also internally during the Great Jewish Revolt of 66 CE and the Bar-Kochba Revolt (132-135 CE). Located south of Cappadocia and west of Mesopotamia, Syria became a Roman province in 64 BCE. For the 1st and 2nd centuries CE, it was a single province, with only one legion stationed there most of that time. However, Roman emperor Septimius Severus (r. 193-211 CE) divided it into two: Coele Syria with Legio IV Scythica and Legio XVI Flavia Firma and Syria Phoenice with Legio III Gallica.
This is a companion discussion topic for the original content at https://www.worldhistory.org/article/1921/legions-of-syria/.