War dogs - Greg Bear

The Gurus came in peace, bearing gifts.

They were a highly advanced, interstellar species who brought amazingly useful and sophisticated technology to the human race. There was, of course, a catch. The Gurus warned of a far more malevolent life form, beings who have hounded the Gurus from sun to sun, planet to planet, across the cosmos. Pundits have taken to calling them the Antagonists - or Antags - and they have already established a beachhead on Mars. In exchange for all they've done for us, the Gurus would now like our help.

Enter Master Sergeant Michael Venn, a veteran Skyrine (a Marine who is specially trained for off-world combat) who is dropped onto the Red Planet with his band of brothers on a mission to take down as many Antags as possible.

But from the moment they're dropped through the thin Martian atmosphere, their mission goes horribly, terribly wrong. From a group of female special ops Skyrines with secret orders, to mysterious humans who've settled on Mars, to the overwhelming and highly-reinforced Antags themselves, Venn and his brothers will face impossible odds just to survive - let alone make it home alive.