I read novel a kingdombuilding novel a couple years ago. It was about two brothers , one took back the kingdom/empire and was facing a strong enemy but the enemy got beaten by his brother soldier in a silver armory or something. The elder brother soldier slashed the enemy and killed it easily and saved the younger brother. And the elder brother was on a mountain with his troops waiting for enemy army.
I can't remember the novel and I would appreciate if you could tell it's name.