Did the Soldiers who saw awful things on the battlefield at the start of the war then kill themselves four years later on a different battlefield?
No, but many of them came back home and killed themselves later.
While you are on the job you are on the job. It is only later when you try to forget the job and find that it is not possible that you begin to despair.
See post 29 or 31. The analysis in that article reports a figure of <1 per day, with caveats about incomplete information.