The comment "why then do the army or police not provide their own units for vets with mental health problems ?"
Reminds me of my experience with someone close to me. I don't know about other countries, but the NZ army has a system and I've seen it work. My mate was in the NZ army for some years and served in Bosnia with the UN Peace Keepers and NATO, he had a particular role there so he came back 'messed up' and was so for some years. Fortunately support was (and still is) there to help him out.

In general, if a country expects people to fight and die, there should at least be quality support for those that return home.