I've had to remove your question because the title is, well, unfortunate. We do try to keep it very safe for work here, which does include curse words. However, your question is easy to answer: It's not true. It has to do with media depiction rather than reality. The truth is that war, as a rule of thumb, messes people up. If you use your search function (and our list of popular question), you will see plenty of topics on PTSD throughout history.