WHY AMBROSIUS AURELIANUS WAS PUT IN BRITAIN: A MYSTERY SOLVED

[Another unfinished piece that was lurking in the 'unpublished drafts' of my blog site.  Just putting it out there, rather than allowing it to continue to stagnate.]

Emrys Wledig. A crude illustration from a 15th century Welsh language version of Geoffrey of Monmouth’s "Historia Regum Britanniae".

Although I have shown to my satisfaction why Ambrosius Aurelianus was not only wrongly placed in Britain, but put there at the wrong time, I've been asked a very good question by some of my readers:  "That's all well and fine, if we're talking about the tradition recorded in Nennius and subsequent sources (like Geoffrey of Monmouth's pseudo-history).  But what about A.A.'s appearance in Gildas?  How do you account for that?"

As it happens, that is an excellent question.  And not an easy one to answer.  But I will take a stab at it, in any case.

A.A. was Prefect of Gaul (and thus of Britain as well) c. 337-340.  We do not know when he died, but his son St. Ambrose (with whom he was conflated in Welsh legend) moved to Rome with his mother not earlier than 353 (https://books.google.com/books?id=sc49DwAAQBAJ&pg=PA7&lpg=PA7&dq=st.+ambrose+and+his+mother+went+to+rome&source=bl&ots=7w4smM9os3&sig=ACfU3U0AuKyqO3hjZIrPlxdpBvQVvfCZ5g&hl=en&sa=X&ved=2ahUKEwi_hL-SzqnpAhUOsp4KHZLYANQQ6AEwDHoECAgQAQ#v=onepage&q=st.%20ambrose%20and%20his%20mother%20went%20to%20rome&f=false).  Some have thought A.A. may have fallen at the same time as his Emperor Constantine II, who died in 340. 

In 343, Constantine's brother Constans, the new Western Emperor, visited Britain.  It is not known precisely why (see http://www.roman-emperors.org/consi.htm#9), but the reason is hinted at in Ammianus:

Book XX

1 1 Lupicinus, master of arms, is sent with an army to Britain, to resist the inroads of the Scots and Picts.

Such was the course of events throughout Illyricum and the Orient. But in Britain in the tenth consulship of Constantius and the third of Julian raids of the savage tribes of the Scots and the Picts, who had broken the peace that had been agreed upon, were laying waste the regions near the frontiers, so that fear seized the provincials, wearied as they were by a mass of past calamities. And Julian, who was passing the winter in Paris and was distracted amid many cares, was afraid to go to the aid of those across the sea, as Constans once did (as I have told),1 

1 In one of the lost books; it was in 343.

Let us suppose, for the sake of argument, that A.A. did not perish with Constantine.  That although he was no longer serving as Prefect of Gaul, he accompanied Constans to Britain in some capacity.  This is certainly not out of the realm of the possible.  Granted, Constantine I/the Great had made the praetorian prefecture a civil, rather than a military post.  But A.A. could have been replaced by another prefect, and found himself in another role as part of a major military expedition to Britain.  It's also not inconceivable that A.A. fled to Britain after Constantine II's death, although had that been the case we would have expected him to take his family with him.  

However it happened, if A.A. was in Britain at the time, how do we account for the sequence of events in Gildas?

Rather easily, I suspect.  The problem has to do with a simple confusion of the two emperors named Constans - the one who was in Britain in 343 and the Constans II, son of the Constantine III who had been proclaimed emperor in Britain in 407.  It is thought that Constantine III actually named his son Constans after the son of Constantine the Great.  

A very puzzling line in Gildas has not, to my knowledge, been analyzed.  It occurs in 25:2, and runs as follows:  "After a time, when the cruel plunderers had gone home, God gave strength to the survivors." These survivors, and those who flocked to them, had as their leader A.A.  On the surface, this would seem to be a nonsensical statement.  The Saxons invited in by Vortigern did not, in fact, go home.  Gildas had just previously told us that they had invited in more of their kind and proceeded to take over the island. We are told in Nennius that Vortimer pushed them to the Isle of Thanet, but that after he was slain they continued their depredations and conquest.  

So who went home when A.A. showed up on the scene?

I would propose that Gildas' account is here hopelessly confused.  The enemy that withdraws in this context was forced to do so by Constans I, perhaps accompanied by A.A., who conceivably may have held the military command.  We are probably talking about Scots and Picts, not Saxons.  What we appear to have here is a simple jumbling of fourth and fifth century events.