The basic concept is to write the dream out as a story. Get it down on paper as soon as possible after having the dream. If it is a recurring dream, you can probably write it anytime. Then, you rewrite the most traumatic part and change it just a little so that it is less traumatic. For example, if in your dream you are in a car accident that killed someone. Keep everything the same in the dream, but instead of the person dying, they get critically injured. So the accident still happens, just the most traumatic part is changed a little. Read this new story each night before you go to bed until you start dreaming the dream with the changed event. (This usually takes a couple of weeks.) Then, change it again, just a little more. Maybe the person is injured, but only goes to the hospital and then is released. Keep changing it little by little until the dream is tolerated better. It can be a long process but is a way you can control what happens in your dreams.
This is the main concept Allen has followed. However, instead of changing the parts of his dream, he puts in self affirming terms that help him realize he is safe. For example, Allen has a recurring dream of the night he was injured by the IED. He spent time writing it out and has started to reread it. When he feels that first tinge of anxiety, he puts something in that spot in the document that says, "You are safe now," or "You are back in the States," or "this is just a dream." He has several phrases he has come up with to write into those places that first start his rise in anxiety in reading his story. He then highlights them, puts them in a box, or makes them bold to make them stand out. They are the words he is initially drawn to when he reads through the dream. This process took him several days to be able to get through it without having a break down. But, he did it. Now he tries to read through it through out his day so that he is comfortable with it. It now isn't causing the feelings and anxiety it originally was creating. His nightmare has also been much less intense since doing this.
He now is creating a dream journal on his desktop to keep track of his nightmares and where he can do this with each one as he experiences it. He has several that seem to recur. This is neither a quick or easy process but Allen has experienced some success with it. Just thought I'd share.