alternatehistory.com

What if Count Theodosius after becoming Comes Britannia install his son as Dux? With the defeat and end of the great conspiracy, how would father and son's ambitions pan out.

This is in conjunction with the POD death of Valentinian I against the Alamanni at the battle of Solicinium where instead of surviving he dies during the brutal battle. Leaving his son Gratian behind in Augusta Trevororum instead of taking him across the Rhenus.

Severus & Jovinus, the men who most scholars say went to Britain to quell the rebellion in this scenario never went and merely were reconnaissance for the armies of Valentinian to gauge an appropriate response to the issue in Britain, survive and with Jovinus on the northern shore against Saxon and Frankish invaders whilst Severus maintained the border between Rome and the Alamanni and others. With a surviving Gratian under one of their guardianship also.

What impact and implications does this have for the empire?

Apologies for how this is written guys, the idea just popped in my head for a story.
Top