A good day to die - Keith R. A DeCandido

Newly inducted into the prestigious Order of the Bat'leth, Captain Klag, son of M'Raq, leads the crew of the Gorkon into the unexplored Kavrot Sector in search of new planets on which to plant the Klingon flag. There they discover the Children of San-Tarah, a species with a warrior culture that rivals -- and perhaps exceeds -- their own.
Klag could call in Gneeral Talak's fleet to bring the world under Klingon domination -- but the San-Tarah offer a challenge he cannot refuse. The Gorkon crew and the San-Tarah will engage in several martial contests. If the Klingons lose, they will undertake never to trouble the planet again. But if Klag and his men are victorious, the San-Tarah will cede themselves to the Empire, and Klag will have single-handedly conquered an entire world.
This is the first tale in a glorious adventure that will be remembered in song and story throughout the Empire...