In Britannia 600 AD field armies are 12 elements (plus camp follower) in DBA or 24 AP in HOTT. The army lists below allow much larger numbers than this for two reasons. Firstly and mainly, to allow choice. Secondly, to allow a larger than normal field armies to be used for a more involved campaign.
I have tweaked the DBA army lists, partly because some of them don’t really match what we know about the protagonists, and partly to support fantastic elements suitable for a HOTT campaign. After a general discussion of the Common Elements, both Realistic Troops (DBA + HOTT) and Fantastical Troops (HOTT), I then look at the specific national army lists. For our purposes there are only five types of armies: Welsh, Picts, Saxon, Irish, and Scots.