sentences:  The historian Ammianus Marcellinus, circa 320-395, is the only source detailing the initial invasion of Armenia.Southern (1999, 149) dates the invasion to 295; Barnes (1982, 17, 293) mentions an earlier, unsuccessful invasion by Narseh based on the fact that the title "Persici Maximi" was given to all four emperors; Odahl (2004, 59) concurs with Barnes and suggests that Saracen princes in the Syrian desert collaborated with Narseh's invasion.Narseh then moved south into Roman Mesopotamia, where he inflicted a severe defeat on Galerius, then commander of the eastern forces, in the region between Carrhae (Harran, Turkey) and Callinicum (Raqqa, Syria).