General Staff. It then numbered six persons, including clerks, and was located in the red brick Navy Ministry building in Tokyo. Among its early members were the young naval officer Hideya Morikawa, nephew of Chief of Staff Admiral Kanji Kato, and Morikawa's former superior, First Lieutenant Kamisugi, who had handled cryptography aboard the flagship Nagato. Captain Kowalefsky, the Polish cryptologist who had improved the codes that Yardley had solved, lectured on cryptanalysis, and the neophyte codebreakers cut their eyeteeth on the GRAY code of the U.S. Department of State, making their entry through the classic technique of identifying NADED as period.* *Whether this solution was made in cooperation or in competition with the Ango Kenkyu Han, the Foreign Ministry's cryptanalytic section, is not known. They also solved Chinese cryptograms during the Manchuria incident, primarily because these were based on a commercial codebook that
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