It's curious that this was marketed as a young adult novel--yes, the protagonist is young and the book is short (196 pages), but it's a regular novel that some teens would enjoy if they are advanced readers. It even has a brief mention of sex (that was Robert Heinlein's definition of his juvenile novels: short adult novels with no sex). In 4th century Britain, 23-year-old Centurion Alexios Flavius Aquila, in disgrace with his superiors, is exiled to take charge of the native Frontier Wolves. He grows into the command, gains the respect of the hardbitten Wolves, and makes friends with Cunorix, son of the local chieftain. It's really about career: recovering from failure, learning a new job, dealing with the stupidity of management (Praepositus Montanus comes to visit and starts a chain of tragic events)--also touching on friendship, betrayal, and courage. Sutcliffe has a knack of making the past live. Most of her books seem to feature stoic male protagonists and lots of battles; they fit seamlessly into the stiff-uppper-lip school of British boys' stories that I was weaned on.
Features the new-to-me word "kalegarth," which isn't even Googleable--now it is!--or in the OED. Looks like it's more commonly spelled "calgarth" and means "kailyard": "a cabbage garden, kitchen-garden, such as is commonly attached to a small cottage." Here's the context: "...this country that they knew as a man knows his own kalegarth."