Of course war-related trauma has always existed. The change has been cultural. In the past men were expected to "suck it up" and "be a man", meaning it was not masculine to show mental weakness. Now men can admit to having PTSD without society considering them weak or unmanly.
It was misunderstood but still viewed with sympathy:
That was a shell shocked soldier from WW1, ostensibly cured at end of video.
If you read the poetry at the time the cannon fodder knew exactly what was happening and how they were being used as pawns. They also describe how traumatised people (and themselves) are. 80,000 people dying in a day with no gain made, seeing friends choke on chlorine gas, seeing people's feet rotting from the water in trenches. Shit was horrible and they went over in the millions in the deluded belief that war was romantic - dulce et decorum est pro patria mori.