Also via naraht. Maybe earlier than what you're looking for, but I enjoy Diana Gabaldon's Lord John series (late 18th century) because it's m/m and NOT romance - there are romantic encounters, but the stories are mystery/adventures, not romances. (I also don't like romance as a genre, but give me m/m adventure with an incidental relationship and I am all over it.)

And, way earlier than what you're looking for, but Rosemary Sutcliff's version of Arthurian history, Sword at Sunset, has a canonical m/m warrior couple as minor characters.