Description
The M-209 was a cipher machine invented by Boris Hagelin or AB Cryptoteknik at the beginning of WWII. As a pin-and-lug cipher machine, it did not require electricity. During the war, German cryptanalysts called the machine "AM-1" for "American Machine #1".
In 1942, cryptanalysts from the US and UK had a debate over this machine. The British were concerned that the Italians would be able to read American Hagelin traffic, as they had been able to read Italian Hagelin traffic. However, the US chose to ignore this- citing that breaking the M-209 would be too difficult and time-consuming for the Axis powers. As it turned out, the Germans were able to read ~10% of American Hagelin traffic. This was 6% due to cryptanalysis and 4% due to captured keys. However, this decryption usually took 7-10 days- often rendering the message old and not useful.