In the Name of Honour by Richard North Patterson
The McCarrans and the Gallaghers, two families with deep ties to the military, have been close for decades, ever since Vietnam. Now a new generation of soldiers is fighting on a distant battlefield, and Lt. Brian McCarran, the distinguished general's son, has recently returned from a harrowing tour in Iraq. Traumatized by his war-time experiences, Brian depends on his lifelong friendship with Kate Gallagher, who happens to be married to Brian's commanding officer in Iraq, Capt. Joe D'Abruzzo. But Kate is dealing with trauma of her own: since coming home, D'Abruzzo seems a changed man, and lately he's become paranoid and abusive.
Tragedy strikes when Brian shoots and kills D'Abruzzo on their army post in Virginia. Brian immediately confesses but claims self-defense-D'Abruzzo, a black-belt martial artist, came to his quarters, accused him of having an affair with Kate, and attacked him. Or so Brian says and now he faces a high-profile court martial. Before the case is over, they will all learn that families, like war, can break the sturdiest of souls.