In February 1942, General Rommel's Afrika Korps pummeled U.S. forces in North Africa, and the Americans became worried that their defeat would encourage fascist Spain to join the Axis alliance. Moreover, the Germans were amassing troops in Morocco, in preparation for cutting off the railroad from Casablance to Algiers — the sole supply line for Allied forces. A covert operation was needed to debilitate the German troops, break the momentum of the Axis, and save the Allied lifeline... This called for flies.

The plan was to weaken the enemy forces by using flies to spread a witch's brew of pathogens. Given the agency's inability to rear an army of flies, [OSS Research Director] Lovell decided to conscript the local vectors...

Lovell was a chemist, but he'd been out of the laboratory often enough to know that flies love dung. And with a bit of research, he discovered a key demographic fact: There were more goats than people in Morocco — and goat are prolific producers of poop. Lovell now had the secret formula: microbes + feces + flies = sick Germans. Now all he needed was a few tons of goat droppings as a carrier for laboratory-cultured pathogens.

The OSS collaborated closely with the Canadian entomological warfare experts to launch one of the more preposterous innovations in the history of clandestine weaponry: synthetic goat dung. Of course flies are no fools; they won't be taken in by any old brown lump. So the OSS team added a chemical attractant. The nature of this lure is not clear, but a bit of sleuthing provides some clues.

Allied scientists might have crafted a chemical dinner bell by collecting and concentrating the stinky chemicals that we associate with human feces (indole and the appropriately named skatole). While these extracts would have worked, the more likely attractant was a blend of organic acids, some of which had been known for 150 years. Two of the smelliest of these are caproic and caprylic acids, which, by no coincidence, derive their names from caprinus, meaning "goat." Etymologically as well as entomologically astute, Lovell named the operation Project Capricious. So with a scent to entice the flies, Lovell's team then coated the rubbery pellets in bacteria to complete the lures.

All the Americans had to do was drop loads of pathogenic pseudo-poop over towns and villages where the Germans were garrisoned, and millions of local flies would be drawn to the bait, pick up a dose of microbes, and then dutifully deliver the bacteria to the enemy. Lovell worried about keeping the operation clandestine. The Moroccans had to be persuaded that finding goat droppings on their roofs the morning after Allied aircraft flew over was a sheer coincidence. Presumably a good disinformation campaign can dispel almost any suspicion, or, as Lovell intimated, if the plan succeeded there would be very few people in any condition to raise annoying questions about fecal pellets on rooftops...

In the end, however, Lovell didn't have to worry about getting caught by either friends or foes, as the secret weapon was never deployed. Just as the OSS was gearing up to launch the sneak attack, the German troops were withdrawn from Spanish Morocco. They might well have preferred to take their chances with pathogen-laden flies, given that Hitler was sending them to the bloody siege of Stalingrad.