In chapter 7 Bruno is talking to his mom about Harr Roller, also known as Franz. Bruno dismisses him as crazy because he fights with his shadow and invites cats to tea. However, his mom tells him not to laugh. She says:
It's nothing to laugh at. You have no idea what the young men went through back then. Their suffering (68).
This is an example of dramatic irony in relation to the larger idea of the book. At this point in the novel we have not seen the entire significance of Brono's proximity to a concentration camp, but from what we know about history in general we can understand the irony of this statement.
Bruno's mother is sad because Franz used to be a great dancer, and clearly someone she thought was charming. She says it is sad that this happened to him, that such a wonderful person was destroyed. She calls it the Great War because World War I was called the Great War before World War II, and since WWII is the setting of the novel we can directly draw the connections between her sorrow for what happened during the first war into what happened in the second. However, she herself does not see the parallels.
Her comment of sympanthy for the victoms of WWI should extend into sympathy for the victoms of WWII, but because she is living in that moment she can not see the parallels.