…Antioch, where the official version of events…
296 CE
…Antioch, where the official version of events is made clear: Galerius is to take all the blame for the affair.
In Antioch, Diocletian forces Galerius to walk a mile in advance of his imperial cart while still clad in the purple robes of an emperor.
The message conveyed is clear: the loss at Carrhae is not due to the failings of the empire's soldiers, but due to the failings of their commander, and Galerius' failures will not be accepted.
(It is also possible that Galerius' position at the head of the caravan is merely the conventional organization of an imperial progression, designed to show a Caesar's deference to his Augustus.)