Although it sounds reprehensible, battlefield plundering was a common -- and often necessary -- practice during the War Between the States. As the conflict dragged on, equipment wore out or was lost, and replacements were often not forthcoming. Re-outfitting ragged, shoeless soldiers was an especially difficult task in the Confederate Army. The Union blockade had slowed the flow of manufactured goods such as arms and other military equipment to a mere trickle, despite the best efforts of the blockade runners to keep the government supplied with what it needed. Confederate manufacturing was simply incapable of making up for what the blockade runners failed to bring in.
Just as weapons and ammunition were taken from the dead and wounded during battle, so were shoes, boots, overcoats, rifles, haversacks, canteens, and food taken from those who no longer needed them in the aftermath of a battle. Other items, such as the locket that is the subject of this song, were taken either as personal trophies or with an eye toward resale or barter with the sutlers who followed the armies.
"O! Touch Not My Sister's Picture"