What is the true meaning of the song, "The Night They Drove Old Dixie Down?"?

The lyrics tell of the last days of the American Civil War and its aftermath. Confederate soldier Virgil Caine "served on the Danville train", the main supply line into the Confederate capital of Richmond, Virginia. General Robert E. Lee's Army of Northern Virginia is holding the line at the Siege of Petersburg. As part of the offensive campaign, Union Army General George Stoneman's forces "tore up the track again". The siege lasted from June 1864 to April 1865, when both Petersburg and Richmond fell, and Lee's troops were starving at the end ("We were hungry / Just barely alive"). Virgil relates and mourns the loss of his brother: "He was just eighteen, proud and brave / But a Yankee laid him in his grave".