Some enterprising Chinese alchemists invented gunpowder in the 9^th century. The formula is simple: saltpetre, sulfur and charcoal.  It helps if you have millions of bats because guano (dried bat feces) breaks down into saltpetre—  or potassium nitrate to you chemists. 

Texas has millions and millions of bats and hundreds of bat caves. Bracken Cave, near San Antonio, is home to 20 million Mexican free-tailed bats every summer. It’s the largest Mexican free-tailed bat colony in the world that’s open to the public. The second largest such bat colony in the world is west of Bracken, near Concan in Uvalde County, where the Frio Cave is home to another 10 million or so bats.

These two Texas caves and a couple of dozen others became defacto ammunition plants during the Civil War because 30 million bats produce massive amounts of guano which can produce a lot of gunpowder. The Confederacy needed that in the worst way after a Union blockade cut off virtually all Confederate supplies. 

The Hill Country was also well-suited to produce saltpetre (pronouced and sometimes spelled saltpeter) not only because of its millions of bats and the tons of guano they produced but because enterprising souls in the Hill Country knew how to make charcoal by burning cedar. 

An item in the Richmond Times Dispatch of Dec. 30, 1861, noted the sudden interest in saltpetre:  “The Houston (Texas) Telegraph learns that an effort is being made in Burnet to manufacture gunpowder, and that it is likely to prove successful. A cave was discovered, not long since, in Burnet County, which was said to contain saltpetre in an almost pure state. A Mr. Foster of Burnet visited the cave, taking with him a few pots, and in about two weeks he returned with 150 pounds of pure saltpetre. He at once set about the manufacture of powder and we are promised a specimen of the result.” 

Frio Cave is a good example of how the local industrialists of the day mined saltpetre, and it’s one place where you can see evidence of this particular enterprise in the form of ruins from the drying kilns that were used in the process.  A narrow-gauge railway with mule-drawn cars hauled guano from the cave, and workers dug pits to make charcoal. They saved one room of the cave as a corral for the mules. Local farmers later mined the cave’s guano for fertilizer until cheaper and more efficient fertilizers came along that didn’t require mucking around in guano all day. 

Eighty years after the Civil War, the U.S. Army again eyed the Hill Country bats for a major war effort, World War II. The Army no longer needed guano to make gunpowder but certain strategists thought it would be cool to turn the bats themselves into tiny incendiary bombs and drop them on Japan. The bat bombs would set Japan on fire and demoralize the Japanese people. Genius! All the Army needed was enough bats to burn down Japan.  

The plan involved refrigerating the bats into hibernation and then outfitting them with tiny parcels of napalm and itty-bitty parachutes and dropping them from airplanes on Japanese cities, which would burn to the ground as the bats flew hither and yon, sparking small explosions wherever they went. 

It would’ve worked if only…actually, it never had a chance. 

The first problem was getting the bats to go into and emerge from hibernation on schedule. Also, the itty-bitty napalm bombs needed to be even smaller and the parachutes needed to be a wee bit bigger. During a trial run in the states, most of the bats hit the ground without ever waking up.  A few bats survived the free fall and flew into the nearest buildings, as expected.

Unfortunately, the nearest buildings were airport hangars at a brand-new U.S. airfield. One disoriented but combustible bat flew into a general’s car, and the idea of bat bombing Japan went up in smoke. The army instead turned its attention to another secret weapon, the atomic bomb, and the bats resumed their peaceful pursuits.