What is the main conflict in Word of Honor by Nelson DeMille?

Ben Tyson is on a train bound for his work when a book being read by a fellow commuter catches his eye. The book, "Hue: Death of a City," describes the actions of Tyson's platoon on a particular day during a battle in Hue, a Vietnamese city. The author, Andrew Picard, cites two unnamed members of Tyson's platoon and an unnamed nun as his sources of information. Tyson immediately realizes that the story is the account of the murders of several civilians by American troops under his command, and knows that under military law he can be held accountable for those crimes. The problem is that he can't be tried as a civilian for military crimes and so he is soon recalled to the Army and assigned to Fort Hamilton where he's placed under restriction to remain on post.