As toilsome I wander'd Virginia's woods,
To the music of rustling leaves kick'd by my feet, (for 'twas autumn,)
I mark'd at the foot of a tree the grave of a soldier;
Mortally wounded he and buried on the retreat, (easily all I could understand,)
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After the Civil War, Whitman encounters the grave of a soldier and honors him, and long remembers this encounter in the woods.
Haunting. Whitman is absolutely haunted by the death of men in war. He shares these feelings with us so well that now we are haunted by that grave of a soldier found in an autumn stroll through the woods