The scene where Col. Grady's wife pleads with him to stop the attack
At this point there must have been some considerable doubt in Col. Grady's mind if he was doing the right thing or not. He already heard from someone who sounded like the President ordering him to turn around. Now he's hearing his wife's voice pleading to him to stop.
One thing they should have done is have the wife mention things, personal details that only she and Col. Grady would have known between each other to convince him to stop.