What is the theme in The Eye in the Door by Pat Barker?

The theme of trauma runs through the entire narrative. Primarily, combat-related trauma concerns most of the main protagonists in the story. Billy Prior, Charles Manning, and Siegfried Sassoon all suffer from war-related trauma. Each man's symptoms manifest differently, but they all share the experience of having been significantly altered by their combat experiences. Billy is physically wounded. Charles Manning's leg is damaged almost beyond repair in France and Siegfried Sassoon first becomes a victim of shell-shock and is subsequently shot.