The Wrong Side of Space by Britt Ringel
Lt. Commander Heskan and Komandor Lombardi have only one thing in common - the will to survive.
Bitter rivals for over a century, the Brevic Republic and the Hollaran Commonwealth are at war. Cultures that shared a common Terran ancestry have been separated for generations. Now, Heskan's escort ships must protect Lombardi's heavy cruisers as they are forced to run together into unexplored space from a devastating, new threat. Each commander faces dissension in the ranks, even as they try to unite their fleets and find some way to escape the fate of so many of their fallen comrades. For the duration of the tenuous truce, there is a singular objective... make it home.
Yet there can be only one destination at the end of their journey, and only half of the fleet will be safe, if they can reach the Republic or Commonwealth at all. If the warring governments cannot be trusted to secure safe passage of the allied crews, how can the two commanders trust each other?
Author's Note: This is Book 3 in the This Corner of the Universe series, continuing the story of the original crew of BRS Anelace and her captain.