Quote Originally Posted by Thoros of Myr
With Brittania I was already fighting with the Dacians and Germania who they were enemies with so maybe they figured I would help them?
Ah-ha... After looking, I realised that in all three campaigns I've got going, I'm allied with their worst enemy. Ha! That'll teach me to look at my Allies panel more often. That makes sense, thank you very much Thoros!