Having lost a fiancé and many friends in Vietnam, and also working for the US Army most of my life, I learned that a 'war zone' changes a person extremely. There are many stress factors involved and some don't even want to talk about their tours... it's just too much to share with people who have never been in that environment.
He might feel that need to experience as much of life as possible before it's lost forever.
He might also be in conflict with himself and his beliefs and just does not know how to express it.
If possible, talk to some veterans about their relationships and how they adjusted to their roles.
Just a thought...
http://smileys.smileycentral.com/cat/15/15_9_16.gif Nothing works well at long-distance, it takes strength, trust and stamina, above all understanding.