The French resistance and Allied bombers weren't the only threats that Hitler's Nazi soldiers faced in Paris during World War II. Turns out syphilis -- spread from dalliances with French prostitutes -- presented a more clandestine danger, reveals a new book.

To combat Nazi soldiers' temptations from the Parisian joie de vivre, Hitler gave the OK to manufacture blow up sex dolls as a more (ahem) hygienic alternative, reports The Herald Sun.

The sex dolls were apart of "the Borghild Project," a top secret 1940 mission inspired by SS chief Heinrich Himmler, who first alerted Hitler of the syphilis problem, according to The Daily Mail.

"The greatest danger in Paris is the widespread and uncontrolled presence of whores," Himmler reportedly wrote.

The project focused on creating smaller-than-life-sized dolls that would fit into a soldiers backpack. As for design, they first approached Hungarian actress Kathy von Nagy to see if she could serve as a model for the doll. But after her refusal, the Nazis unsurprisingly opted for a blue eyed blonde version to "comfort" their soldiers.

After endless tests by Nazi troops in Jersey, 50 were finally ordered up for Himmler's troops. But only two years later the project was reportedly canned when soldiers refused to carry the dolls in fear of embarrassment if captured.

Author Graeme Donald first discovered Nazi Germany's sex doll project while investigating the history of the American Barbie doll for his book Mussolini's Barber, which chronicles the most bizarre untold war tales.