The Imperial crusade, including Gaunt's Ghosts, are sent back to the planet Gereon to join forces with the Imperial defenders and liberate the planet from Chaos. However, the brutality of the 'liberation' pitches Gaunt into opposition with his commanders, who believe victory must be achieved at any price, no matter how cruel.
This book is part of the Gaunt's Ghosts: The Lost Books series and is book #3 in the series.