Where to put your Saxons?

[Arturus Uriconium]

Having said that, I do agree with your ideas about what area the brothers were supposed to guard. Gildas' ideas about British defence seem overly engaged with explaining the 'why's' of the Saxon Coming, anyway. There's no evidence of any 'Pictish Wars' besides his sermon and lament, so they may have been the 'cooked-up' reason to explain why Vortigern and the British Council needed to get Germanic troops anyway. That these had been present in Britain since Julius Caesar brought the first would of course have been unknown to Gildas. And that many Roman soldiers from different parts of Germany had been present in the Late Roman forts of Britain would have maybe suprised Gildas too.

By Gildas' time all reports of any problems with Scotti and Picts could have been merged with stories from various parts of Britannia. They may both have been a problem in the north, circumventing the walls to raid south of it. It could have been Angles who were used here. The Saxons (or whatever they were as Saxon was a generic term) could have been guarding against Saxon pirates, although there's no report of them at the time. Who else do you need to defend yourself against on the southeast coast? Amoricans? Or were they worried about the Franks? Or did Gildas get something right when he said they were there to defend against a Roman threat, either real or imagined?

Maybe we're forgetting that all these peoples - Angles, Saxons, Scotti, Picts, and Britons of course - were seafaring pirates and if the threat was from the sea, who better to use than other excellent mariner warriors. Maybe they weren't landbound in general, but a replacement (or reinforcement) for the Classis Britannicae? (back to the old Saxon Shore question there - was it named after the Saxons who defended it or from them?) If the threat is external, then they're needed on the coasts. If the threat is internal - civitas against civitas or province against province - then they need to be inland as well as at river boundaries. If the problem is both...

Of course we mustn't forget the other part of the H&H story, and that's sending Hengis' two sons, Octa and Ebusa, north to attack the Picts and lay waist to Orkney? Truth? Another myth? Probably just Bede making the Saxons out to be the next Romans of Britannia and doing what they did. But if Pictish pirates did manage to attack Londinium, or even further north, then what better revenge than to attack the Pictish 'powerbase'?

And we don't need a war to need help, just bloody annoying, constant raids. But it all comes back to the question: if they were defending the southeast - Kent and the Thames estuary - who were they defending it from?