Space War 2,
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This review is from: Lines of Departure (Frontlines Book 2) (Kindle Edition)
Two penal battalions are shipped into space and dumped on an ice planet where it is thought that they can't do much damage. This is a mistake - disaffected beforehand, they mutiny when ordered to take over the colony. Of course, that order is illegal - they are meant to be there in suppport of the civilian authorities.
Things go rather more piriform when an enormous, invulnerable alien vessel is detected in the star system. It wipes out one Earth vessel without even slowing down.
Then a fleet of starships is detected...
Very realistic space opera - you can believe the characters and the technology described. Miguel Alcubierre (the famous Mexican astrophysicist) must be delighted to see his theories at work...