TheCodeBreakers
in 1925 with the creation of an ultra-secret Tokumu Han ("Special
Section") in the 4th, or communications, Department of the Naval
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.
annaabi.ee 
