Ah, with your update it helps.
Of course he is completely concerned about his father. He is feeling helpless because he does not have control over this. He is afraid of the worst nightmare any child can have. Their parents will die. He can not save him. He is worried also that what will happen if something happens to YOU.
This is just as important of a conversation as what if his father is killed? He is keeping you in his sights, so he always know where you are. He probably thinks if he can see you or be next to you, nothing can happen.
Have you spoken with him about how you are safe? About how he is safe? Have you spoken about how moms used to be daredevil girls growing up but now that they are moms, they are extra careful so they can be healthy and hardy to take care of their children?
We live in the tiniest house. 2 bdrm/1 bath, but our daughter could easily get spooked even during the day. We purchased a pair of walkie talkies for her to use. These were no to be used at night. Night is for sleeping.
At night we played soft music or played a book on CD, so that she could clear her mind of the scary thoughts that ran through her mind. She is an extremely creative child so she could think of all sorts of horrible things.
We also used "Dream coins". These are magical talisman that when placed under his pillow will give him a good sleep. They protect him from scary thoughts and dreams. (purchase some foreign coins.. (have multiples in case they get lost). Give it to him during the day and have him place it under his pillow so tonight, he can see it is still there. He will be able to sleep with his hand under his pillow on the coin and know he is safe.
My mother used to relax our daughter when she was too antsy to sleep by turning off all of the lights and starting with her hand, soflty touch our daughters head and very slowly and calmly say, "it is time to rest, rest your head".. Then she would move to her "forehead, with a slight touch "it is time to rest your forehead.". She would continue all the way to her feet.. She did this each night our daughter slept over at her house..
Eventually my mother says once she got to our daughters chin, our daughter was out..
Therapy for all of you is going to help. This fear is real. I do not blame him. Remember to children, their parents are their whole world.
I think for adults if their husbands, wives or children are in the military, it takes a lot of effort to not shut down and want to sit in a corner and weep till their loved one comes home safe. So imagine the terror your son is feeling. He has not control over anything, except staying as close to you as possible. He needs some tolls to help him feel safe.
I agree with Linda. What exactly is he afraid of?
Sounds, the darkness, under the bed, the closet?
How long has this been going on?
How long has his dad been in Afghanistan?
How long have you been remarried?
How long have you lived in this house?
Did he just start school?
Is this week his first week of school?
Has something changed?
Once you have heard from your son and thought about what has changed.. then you may have a better idea of how to help him.
We need more info.