Vengeance (Star Legions: The Ten Thousand Book 7). Star Legions: The Ten Thousand, #7

The Black Legion bursts out of the Median Empire laden with riches and leaving a trail of death and destruction in its wake. As the exhausted men and women breathe a sigh of relief upon reaching the Free Colonies of Trebizond, they are stunned to find themselves in the middle of a war. A mighty coalition of local warlords and mercenaries, with the illicit support of the Median Empire has betrayed their neighbours and struck at the powerful Trebizondan fleet.
Large numbers of warships are poised to overwhelm the system and turn it into another fiefdom of the Empire. Sensing the danger, Xenophon hurls his contingent of ships into the fray to help his fellow Terrans. Trailing in the rear, the broken and battered ships of the Black Legion struggle to catch up. For the brave men of the Legion, this is more than a battle to save Trebizond. This will be their final act before the Legion disbands and they return to their homes.
For Xenophon this conflict is all that stands between him and vengeance against those that betrayed him, and murdered his family and friends. Vengeance is the seventh book in the Star Legions series by Michael G. Thomas, the bestselling author of the Star Crusades series.