Conan of Venarium — Harry Turtledove

On the verge of adulthood, young Conan of Cimmeria confronts disaster in his homeland: an attack by the Aquilonian Empire. Conan burns to join the fight, but he's deemed too young. Then comes the grim news: Cimmeria's defenses have collapsed, and the Aquilonians have smashed through and will rule as they please. Soon their forts dot the countryside. Their settlers follow after, making homesteads of other men's land.

Every Cimmerian longs to put the invaders to the sword, but the Aquilonians have promised savage reprisals. Then, intolerably, the Aquilonian commander takes an interest in the young lady who has young Conan's eye. The forces of Aquilonian imperialism have no idea what they're about to go up against....