Rosemary Sutcliff 
Frontier Wolf [EPUB ebook] 

‘We are the scum and the scrapings of the Empire. They tipped out the garbage-bin of the Eagles to make us what we are.’In disgrace after a mistake that cost the lives of half his men, Alexios arrives in Castellum. It’s his first command, but it isn’t really a promotion. The Frontier Wolves who man this outpost in the far north of Roman Britain are a fierce and savage bunch, a far cry from the regular legions he’d served in before. Alexios will only survive if he learns to understand them and win their respect — and he’s determined to try.