War dogs

"They came in peace, bearing gifts. The Gurus were a highly advanced species who brought amazingly useful and sophisticated technology to the human race. There was, of course, a catch. They warned of a far more malevolent life form, beings who have hounded the Gurus across the cosmos. The media have taken to calling them the Antagonists -- or Antags -- and they have already established a beachhead on Mars. For all they've done for us, the Gurus now need our help. Enter Master Sergeant Michael Venn, a veteran Skyrine who is dropped onto the Red Planet with his band of brothers on a mission to turn back the Antag tide. But the Skyrines will face impossible odds just to survive -- let alone make it home alive. "--