Vietnam War

My dad had a friend who was drafted into this war. He took his secrets to his grave about a year ago. Because of his choice to hide the truth, the world will never have true understand from his perspective about what really happened over there. I don’t know if talking about it was just too difficult or if he took an oath to conceal the truth but it seems strange to me that he would cover for a nefarious government so that left me feeling like he personally did something so shameful he couldn’t bear repeating it.