Explanation: In the past, PTSD was not necessarily well-known - while some of the symptoms were intermittently recognized by cultures throughout the years, there was never a particularly clear conception of PTSD like we have today, nor a united approach towards dealing with it. Things were particularly stark in WW1, as serious approaches towards mental health were beginning to emerge in modern states... just as officers sent mentally broken troops back into the trenches, or even executed them for daring to have breakdowns in the middle of a war.
By WW2, things were far from perfect (and things are honestly still pretty fucked today), but there was at least the recognition that PTSD was a serious condition that was not just some moral failing on a soldier's part. Unless you were Patton, but fuck Patton, that prick.