Radko's War. Radko's War, #1

Commander Finn Radko and the crew of the HMCS Vimy Ridge, lone survivors of the greatest massacre in human history, begin a perilous journey through the mysterious attacking armada in the desperate hope of preventing another catastrophe. Undermanned and unprepared for battle, Sergeant Freyja Sigurdsson and her garrison scramble to man their defenses as the unthinkable unfolds: an invasion. Marching through the blowing snow, an alien horde; their identity unknown, their capabilities devastating.
As the galaxy burns, Radko and Sigurdsson face the destruction of all they know and love, and must pull together a coalition of unlikely allies with the fate of humanity resting on their shoulders. One ship against an armada. Thirty soldiers against an army. The future of the human race hangs in the balance.