of the Pearl Harbor attack. The ads were headlined "Achtung, Warning, Alerte!" and showed an air raid shelter and a pair of white and black dice which, despite being six-sided, carried the figures 12, 24, and XX, and 5, 7, and 0, respectively. It was suggested that these could possibly be interpreted as giving warning of an air raid on day "7" of month "12" at approximate latitude coordinate "20" (Roman numeral "XX"). The board game was an actual product with sets sold during this time. Detection of Japanese radio transmissions en route Alleged detection by SS Lurline There are claims that, as the Kido Butai (the Striking Force) steamed toward Hawaii, radio signals were detected that alerted U.S. intelligence to the imminent attack. For instance, the Matson liner , heading from San Francisco to Hawaii on its regular route, is said to have heard and plotted, via "relative bearings", unusual radio traffic in a telegraphic code very different from International Morse which persisted for several days, and came from signal source(s) moving in an easterly direction, not from shore stations—possibly the approaching Japanese fleet. There are numerous Morse Code standards including those for Japanese, Korean, Arabic, Hebrew, Russian, and Greek. To the experienced radio operator, each has a unique and identifiable pattern. For example, kana, International Morse, and "Continental" Morse all have a specific rhythmic sound to the "dit" and "dah" combinations. This is how Lurlines radiomen, Leslie Grogan, a U.S. Navy reserve officer in naval communications, and with decades of maritime service in the Pacific identified the mooted signal source as Japanese and not, say, Russian. There are several problems with this analysis. Surviving officers from the Japanese ships state there was no radio traffic to have been overheard by anyone: their radio operators had been left in Japan to send fake traffic, and all radio transmitters aboard the ships (even those in the airplanes) were physically disabled to prevent any inadvertent or unauthorized broadcast. The Kido Butai was constantly receiving intelligence and diplomatic updates. Regardless of whether the Kido Butai broke radio silence and transmitted, there was a great deal of radio traffic picked up by its antennas. In that time period, it was known for a radio signal to reflect from the ionosphere (an atmospheric layer); ionospheric skip could result in its reception hundreds or even thousands of miles away. Receiving antennas were sometimes detected passively