TheCodeBreakers
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
transformed the Chinese ideographs to four-digit numbers for telegraphic
communication. After the Japanese seizure of Shanghai early in 1932,
Morikawa was sent there as chief of a cryptanalytic unit attached to the
3rd Fleet. He solved a Chinese message that corroborated a slightly
annaabi.ee 
