A newly published World War I diary is considered to be one of the most accurate depictions of the horrors of war. Ernst Jünger, the German diarist, served for 3 years in the trenches on the Western Front. He was wounded 7 times. That he survived the combat theaters he was in at all was a 1 in 20,000 chance.
It is interesting to note that he did not suffer from PTSD. Der Spiegel has the details.
I believe there were two factors which contributed to the diarist’s lack of PTSD. One was the firm belief that what he was doing was right, noble and good. (While the Nazis revered him and tried to exploit his deeds, he himself refused to associate with them.) The other was that he kept a diary, which allowed him to mentally work through any issues as they happened or shortly thereafter.