Recently I was reading stories about the Norwegian resistance during the Nazi occupation of Norway in the Second World War. Many of the activities of the resistance were quite funny, borderline childish. For example there was one operation that involved coating condoms in itching powder before distributing them to German soldiers. The result of this particular operation was an inundation of soldiers (and presumably women as well) at Trondheim hospital who thought that they had contracted an STI. However, the story that most caught my attention was a plot to induce mass diarrhea among the u-boat crews when the Battle of the Atlantic was at its height.
On April 9th, 1940 Adolf Hitler sent the Wehrmacht into Norway in what amounted to a (relatively) bloodless regime change. A puppet government was set up under Vidkun Quisling and his Nasjonal Samling (the Norwegian Nazi party). By the winter of 1940 the Norwegian resistance had begun organizing an intelligence network across the whole country. This network was so successful that the Norwegian resistance soon gained a reputation for being the most efficient and ruthless of all the resistance movements of occupied Europe. However, being in the resistance was not a full-time occupation. The vast majority of Norway’s coastal community were largely subsistence fishermen and of course had to continue supplying their families with food, the most common of which were sardines, as it had been for centuries. Consequently the Norwegian government’s decision, at the behest of the Nazis, to requisition the entire sardine catch came as a huge blow to the Norwegian resistance. However, thanks to their extensive intelligence networks, the Norwegian resistance soon learned the reason behind the mass acquisition of their precious sardines. The sardines were to be sent to the port Saint-Nazaire in Western France, the home of the U-boat wolfpacks that were raiding the shipping lanes to intercept supplies coming from the US and Canada to Britain in an attempt to starve the latter into surrender. The sardines were to be used to supply the U-boats with easily stored food for their long voyages at sea.
Seeking revenge for the theft of their main staple food, the Norwegian resistance contacted the intelligence services in London and requested a shipment of the largest amount of croton oil possible. Croton oil is an extremely powerful laxative from a plant called the Hogwart (yes, like Harry Potter’s school). London complied and the oil was smuggled into every canning factory in Norway where the oil was used to replace the vegetable oil that is usually used to can sardines (the tangy flavour of sardines was also a convenient disguise for the strange flavour of the croton oil). These spiked sardines were then dutifully handed over to the Germans and sent to the U-boat crews. Now diarrhea is bad at the best of times but suffering it in a confined space with a bunch of guys, all of whom are suffering the same thing, must have been a truly hellish experience.
British intelligence were so impressed by the success of the mission that they started to put together their own diarrhea based campaign. In a document titled “Evacuation against evacuation” the British sought to use a substance called carbachol to spike German supplies. Bottles of carbachol were also to be dropped over German defensive positions with labels attached explaining that the German soldiers should drink it to induce illness and so get out of fighting (a less painful, albeit messier, variation of the famous “shooting yourself in the foot” that was used in WWI). However, this plan was never adopted by British command.
Croton oil would also have a rather strange earlier usage in the US navy. Alcohol was banned from US warships in 1914, however, early torpedoes were fueled by ethyl alcohol which was 80% proof. The sailors would therefore use the torpedo fuel, flavoured in various different ways, to get pissed. Naturally this began to worry the US navy. Their first preventative measure was to mix the ethyl alcohol with methanol. Despite telling their crewmen of the danger that methanol can make you blind this did not prevent the torpedoes being frequently tapped for their fuel. Croton oil was seen as the solution to this problem; The crew might not mind going blind but they wouldn’t dare go near anything that would give them diarrhea. Unfortunately they were wrong and the sailors learnt that they could remove the oil by boiling the fuel.