Ranks of Bronze

Ranks of Bronze is a science fiction novel by David Drake.

A defeated Roman legion is sold into slavery to alien traders seeking low tech soldiers to be used in conflicts to secure trading rights on alien planets. Their new masters soon learn that the Romans are the best low tech fighters that can be found. Given their worth as soldiers and success on the battlefield, the Romans' alien masters provide them with everything, including near immortality. However, the Romans want only one thing, and that is to go home.