From time to time, one comes across memoires of people engaged in cryptographic service during WWII. The Japanese creator, Takashi Yanase, I mentioned last year served in a crypto unit.
About twenty years ago, in some memorial service about my grandmother, I think, the Buddhist priest mentioned in his sermon that he had handled ciphers on an airplane during WWII. (I regret I didn't dare interview him at the time!)
Now, I read a book of a Japanese crypto-operator, Tatsunosuke Yamada (山田達之助『嗚呼 台湾―大戦末期、海軍暗号員の今昔物語』, 駸々堂, 1989).
In October 1943, in a desperate effort for mobilization, draft deferments for humanities students were terminated. Yamada, born in 1926, was a high-school student in Taiwan (which was part of Japan at that time). Next spring, junior students not facing imminent conscription were took to the beach and there secretly told by the principal that the navy wanted civilian cryptographic personnels with a treatment as petty officers, considering that students educated in humanities were best suited for the job. Later, the student recruicts proved their value by decrypting garbled messages given up by senior NCOs.
Yamada volunteered and joined the Communication Corps at Kaosiung.
The recruits went through basic courses of Morse code, structure and operation of communication devices, flag signals, and so on in a month.
The advanced course was finished in a day. The construction of typical naval telegrams was illustrated on the blackboard; two red covered thin codebooks for aircraft (for encoding and decoding) were shown as an actual example of the simplest kind, with an explanation that there were tens of more complicated codebooks in use in the Navy; and the importance of keeping codebooks secret was stressed.
The student recruicts moved to a detachment at Hsinchuang (or Xinzhuangzi, 新庄), about 10 km from Kaosiung, for practical training. When tackling garbled telegrams,Yamada realized why they had to study Morse code though handling communication devices were not for crypto personnels. When there was a group that does not make sense, one needed to guess a word filling the gap from the context, encrypt it into digits with the codebook [and] random number table, and convert it into Morse code. If the resultant Morse code was similar to the garbled code group (e.g., the difference is only in one dot missing), the guessed word was adopted. Otherwise, another candidate had to be tried. Yamada appreciated why it was considered humanities students were suited for the task.
After one month of training, the student recruits came back to Kaosiung. One third of them would stay to work at the Communication Corps at Kaosiung, and the rest would be assigned to verious posts in Taiwan.
Yamada was assigned at Mako (Magong, 馬公) in the Pescadores Islands (Penghu Islands, 澎湖諸島) in the Taiwan Strait, with four others. Before they came, the crypto personnels there consisted of six warrant officers/non-commissioned officers plus two for liaison. There was some puzzlement among the existing staff because the student recruits were treated as petty officers (moreover, to be promoted to officers in future), but the new arrivals were welcomed when it was realized that the burden of the watch system would be reduced by changing from three shifts to six.
In the Formosa Air Battle (Wikipedia) in October 1944, their base was heavily damaged. Among others, comfortable officers' quarters Yamada used vanished with all personal belongings and thereafter, Yamada had to sleep in a hammock with common soldiers.
Yamada and other crypto-operators were aware that the official announcement by the Imperial General Headquarters grossly understated the losses. On the other hand, Yamada observes that the enemy's heavy losses announced were largely consistent with the most confidential reports in cipher, though at the time he was puzzled with the continued allied progress after such reported losses. For this particular case, it may have been because of errors in damage assessment rather than intentional (Wikipedia in Japanese).
