Savage by Nature — Jan Domagala

After the events that took place in The Blackstar Gambit General Sinclair is given a new posting given to him by President Takagi. He is to head up the new Offworld Special Intelligence group.
Learning what they had from Tartaran, the planet that the Colonial Confederation and The Elysium Alliance went to war over, the OSI is tasked to find more answers about who was behind the experiments performed on the indigenous life.
Captain Jon Savage, a highly decorated Recon Delta Marine veteran is on vacation with his family when they are attacked by a strange creature. Savage, after seeing his wife and daughter brutally slaughtered succumbs himself to wounds inflicted in the battle.
As Sinclair takes command of his new post he is informed of Savage's condition as his troops had taken his body to their base on Mars where they found something incredible.
Savage had been altered by his contact with the creature.
Where had the creature originated from?
Did the same species who performed experiments on Tartaran have anything to do with this creature, was it too an experiment?
During the search for answers Sinclair and Savage learn something of the race behind it all but they also learn a terrible truth about human history.