This is coolbert: We have all heard about the amazing success the allied powers had during World War Two [WW2] in reading the German Enigma cipher machine. It is said that the ability to read in real time the secret messages being passed between the German commanders drastically shortened the span of the war, saved a lot of casualties, and played a very major role period in the defeat of Germany.

Much less has been written about similar successes against Japanese Army cipher machines. And this does strike me as somewhat peculiar.

A LOT HAS been written about the U.S. Navy and their success with the Japanese Navy's code system [JN-25]. This Navy success was very instrumental in the defeat of Japan during the war in the Pacific theatre. But this was a code system as opposed to a cipher system.

And A LOT HAS been written about the Japanese PURPLE cipher machine. And how U.S. cryptanalysts were able to read secret messages enciphered using this machine. And how reading these messages contributed to success both in the Pacific and the European theatres during the war. However, it seems the Purple was primarily a diplomatic machine. And evidently other Japanese cipher machines were read both before and during the war also. These were [??] variations of the same Enigma machine used by the Germans, at least to my understanding. Beginning with RED, followed by PURPLE, and also JADE and CORAL, all being read by U.S. cryptanalysts. But these do not seem to be Japanese Army cipher machines.

For whatever reason, the Japanese Army version of the Enigma cipher machine was not read until 1943?? This is a surprise to me.

"Colonel Sinkov and his American staff worked on the high-level Japanese Army codes.

Central Bureau did not break any high level Japanese Army codes until mid-1943 with the Water Transport code. Later that year, one main line Japanese Army code was broken." [I believe in this context they are talking about cipher machine in contrast to code].

Why it was not until this late date that the Japanese Army cipher machine was read is not really commented upon. Even by much earlier than 1943 the British and Americans were able to read machine ciphers and do so quite regularly and with proficiency. Since most of these cipher machines work on the same general principles [it seems the Japanese RED machine was a version of the Engima, the PURPLE an advanced version of the RED, and the JADE and CORAL versions yet again of the Engima], it would seem that if you were able to read several cipher machines already, the Japanese Army machine would be an easy target. For some reason this does not appear to be so. Read about the "cracking" of these cipher machines by clicking here.

Perhaps it was the case that in the Pacific theatre, cryptologic matters were given only 10 % of the resources available for analysis. This was the general rule throughout the war, 90 % of the war effort aimed at Germany, the rest toward Japan.

And it must have been that the various allied powers were interested in the activities of the Japanese Army prior to the outbreak of war and did intercept and analyze Japanese Army secret radio traffic.

The British Far East Coordination Bureau [FECB] has been mentioned in a previous blog. Stationed in Singapore prior to the outbreak of war, this unit was based originally in Hong Kong. And excellent location to monitor Japanese radio traffic for the four years Japan was at war with China prior to 1941. There must have been a lot of secret Japanese radio traffic available for the British to analyze.

And H.O. Yardley, the famous American cryptologist, in his book, "The Chinese Black Chamber", describes his mis-adventure in China trying to teach the Nationalists the ways of cryptanalysis. Evidently the Chinese were novices at the science and hired Yardley as a "distinguished" advisor. Yardley was proficient as a cryptanalyst and boasts of having read nineteen different Japanese cipher and code systems during his sojourn in China. These were in all likelihood low level communications, but nonetheless, Yardley was able to demonstrate that the Japanese systems were exploitable. Yardley was later prior to the outbreak of the war contracted by the U.S. government to elaborate on his observations of the Japanese crypto systems, but this effort came to naught [it seems the U.S. was interested in Japanese diplomatic cipher machines without having any traffic of Japanese cipher machines to work on].

So why was it not until 1943 that Japanese Army cipher machines were read by the allied powers in the Pacific? It is a mystery to me?? Perhaps some web sites and histories have this subject covered more fully, but it so, I have not found them.

coolbert.