Traffic analysis, as presented in this post, is based on the experience of members of the On-The-Roof Gang (OTRG) from its origin into World War Two, with one principal target – the Imperial Japanese Navy.

Actually, traffic analysis really starts on the intercept of the initial Morse code “dit” of any transmission.  The experienced intercept operator feels he needs to know the identity of the transmitting as well as the receiving station, the identity of the originator and addressees, the exact frequency used, time of day, operators’ sending qualities.  Some OTRG members had pet names and descriptions of some of the Japanese Navy radio operators who were referred to as those using their left feet on the transmitting key!).  In other words, some Japanese radio operators were very sloppy sending Morse code.

The OTRG intercept operators were trained to copy the Japanese Morse code in Katakana characters using a stick (pencil) or on a typewriter which printed the code into Romaji characters.  If the message was in plain language, and most were until the mid and late 1930s, the same operators, using a very complete Romaji dictionary, would translate those messages while on watch, if time permitted, or between watches.

It was not until shortly before the beginning of World War Two that specific groups were established solely for the purpose of providing traffic analysis.  At Station “C” in the Philippines, four OTRG intercept operators became the first organized Traffic Analysis team: Al Geiken (Class #4, Charlie Johns (Class #13), Ted Hoover, (Class #10 and Duane Whitlock (Class #20).  In Hawaii, shortly before the beginning of hostilities, five OTRG operators were assigned to the decryption center in Pearl Harbor section with their duties limited to sorting traffic for the cryptanalysts.  As best as can be learned, four were identified as Tony Ethier (Class #20), Dick Will (Class #8), Howard Cain (Class #20) and Leo Potvin (Class #14).

Source: NCVA/ Carl Jensen
Edited By Mario Vulcano