There's an Australian patriotic (or anti-war, depending on your attitude) song that addresses that, called "The Band Played Waltzing Matilda", about WWI soldiers in the battle of Gallipoli. The final verse is as follows:
Now ev'ry April I sit on my porch and watch the parade pass before me,
I see my old comrades how proudly they march, renewing their days of past glory
I see the old men so tired stiff and sore, the weary old heroes of a forgotten war,
and the young people ask "what are they marchin' for?"
And I ask myself the same question.
And the band plays Waltzing Matilda, as the old men still answer the call,
But year after year their numbers get fewer; someday no one will march there at all.
The ultimate tragedy would be if these men are "weary old heroes of a forgotten war." We are the guardians of their past, much as they were the guardians of our future.