"Aristotle argued that the difference between horror and tragedy is plot.  Horror just happens, and we learn nothing from it; tragedy is morally insturctive because we follow the story of the tragic protagonist, and can see where he goes wrong and why."

I hesitate to put quotation marks about anything I can't cite properly, but I do not know the origin of this statement.  It is in a book of scraps I collect, and I failed to write down the author.  I am generally frustrated by misuse of the word "tragedy," and this explanation captured some of that.

We are hearing a lot of war stories today.  Contemporary war stories are more horror than tragedy.  We lack some of the narrative and legend that mark the tragedies of earlier wars.  WWI stories are particularly tragic -- or seem so to us, when they were horrifying to the people who were in them, because we do know what is going to go wrong and why.  We even know when.  It is usually after someone says Follow Me Boys.

I recently learned the story of Jack Kipling, Rudyard's only son, who was medically unfit for duty (not to mention 17) but who found a way in thanks to his father's political influence and cultural status.  He lasted about 40 days at the front, and was unidentified for years.  The remains in Jack Kipling's grave are uncertainly his, but there no drive to exhume and identify them.

Some lost soldier lies there.  Jack or not, it is still a tragedy.