First of all, I would suggest that you look at real correspondence from people in real wars which has been preserved. Original sources are important to look at with this question. Many records exist with personal correspondence from soldiers from the Civil War through the wars with Iraq and Afghanistan. Personally, I would want to tell my family that I loved them, that I hated being away from them, and that I hated missing them and what was happening with them. I also think that if I were writing to my spouse, I might share my ideas and fears for the future, and my determination to help my country survive the war and its challenges. If the war were being waged on my country's soil, as opposed to across the ocean, I would be trying to help my family cope with the fear of the war coming near them.