The Last Colony (The Old Man's War series, Band 3)

THEY MUST SAVE THEMSELVES - OR DIE TRYING
John Perry was living peacefully on one of humanity's colonies - until he and his wife were offered an opportunity these ex-supersoldiers couldn't resist. To come out of retirement and lead a new frontier world.

However, once on the planet, they discover they've been betrayed. For this colony is a pawn in an interstellar game of war and diplomacy. Humanity's Colonial Union has pitched itself against a new, seemingly unstoppable alien alliance, dedicated to ending all human colonization.

As this contest rages above, Perry struggles to keep his terrified colonists alive on the surface below - despite dangerous interstellar politics, violence and treachery. And the planet has yet to reveal its own fatal secrets.
'The most entertaining, accessible writer working in SF today'
Joe Hill

'Observant characterization, great dialogue, and some genuinely original science'
Guardian