In 1915, the poster was intended to emotionally blackmail men who – like the person who commissioned it – didn't want to enlist. Today, another reading is seeing the father as someone who did serve, and who knows that his son's toy war is nothing like the reality…
This aspect was the subject of a programme on three men's family links to the Holocaust. It featured two sons of Nazi war criminals. One's glad his father, Hans Frank, was executed for his role as leader of the 'General Government (the bits of Poland that the Germans didn't annex). The other still thinks of his father, Otto Wächter, as someone who was basically good.*
That survives a visit to the ruins of the synagogue used by the third man's relations, and the field where several thousand Jews were massacred, one by one, and still lie buried today. Otto Wächter was ultimately in charge of the auxiliaries who carried that out.
But his son is not the only one who admires him: one of the other things he did was form an SS unit of Ukrainians, known for Nazi political reasons as a Galician division, and many Ukrainians see the Soviet Union as their main enemy in that era and have a 'my enemy's enemy is my friend' attitude to those years, despite the sort of 'friend' Nazi Germany was. (Of course, in the West, the British and Americans took the same attitude to Stalin, to the point of keeping quiet about Soviet war crimes until after 1945.)
And I suspect that many people who've been in a war have horror stories. I think I've mentioned one uncle who served in submarines and risked his own career to try to have his captain charged with ordering the killing of women and children on one Japanese boat they stopped and searched. Coming back full circle, another relation did not talk about what happened in the trenches, even aged eighty.
Perhaps the other reading is more accurate.
* I wasn't the one to tag the neutrality issues with the WP article, but it's got them…
Image courtesy of the Imperial War Museum's Non Commercial Licence – more info about it and the poster at the link.