In 2001, an answer finally came to the supernatural mystery, and it came from an unlikely source: a 17-year-old high school student. Bill Martin was visiting the battlefield of Shiloh with his mother Phyllis Martin, a microbiologist at the USDA Agricultural Research Service. Hearing the story of the glowing soldiers, he thought about another story his mother had told him: the story of the bioluminescent bacteria Photorhabdus luminescens, which glows with a pale blue light. He and his friend John Curtis decided to conduct an experiment to find out if that little critter could be the culprit.

The students found that P. luminescens would indeed have been well-suited to surviving in the mud at Shiloh, but that the inside of the human body was probably too hot. However, they realized that since the soldiers would have been experiencing the cool Tennessee nights from the bottom of a mud puddle in the pouring rain, they may well have been experiencing hypothermia, which would lower their temperatures enough for the bacteria to thrive.

P. luminescens normally survives by hitching a ride on a parasitic nematode and chowing down on the insects that nematode infects. It’s a complicated and somewhat nauseating life cycle that starts up again by creating a glowing insect corpse that attracts more insects to infect. A crucial part of that process is when P. luminescens makes room for itself and for its parasitic host by cleaning up all of the other bacteria in its way. If this glowing duo happened to find its way into a human wound instead of the insects it normally hunts, it’d clean that wound right up. And since it’s not especially infectious to humans (although it certainly can be), P. luminescens is usually no match for our immune systems. There you have it: we wouldn’t recommend introducing a new parasite to fight your infections today, but as Civil War medicine goes, it’s certainly preferable to a field amputation.
There might not be any images of the glowing soldiers on that bizarre battlefield, but the American Civil War is still one of the first wars to be documented with the exactness of photography. Flip through “The Civil War: A Visual History” (put out by the Smithsonian) to see exactly what the brave soldiers of the Union went through. We handpick reading recommendations we think you may like. If you choose to make a purchase through that link, Curiosity will get a share of the sale.