Denzel Washington plays an officer in charge of a tank brigade during the war. The unit he commands is involved in a friendly fire accident that kills one of his own men. After the war he tries to take responsibility for his part in the accident, but his superiors won't allow him to.
Also in the movie Denzel Washington's character seems to have developed drinking problems and other family problems due to his guilt. Whether or not he is actually guilty of anything or not he is consumed by his guilt and states more than once that he just wants to get this investigation right. It is almost as if he feels he can get rid of his guilt by handling this properly.
The character who gets killed is Meg Ryan who doesn't share any screen time with Denzel. Also featured are Matt Damon and Lou Diamond Phillips; members of Ryan's unit.
The filming uses a little known technique known as the Rashomon technique where the versions of each of the unit members are related, and believe me do they conflict ! Watch the film to see to what extent and whether Denzel absolves himself.