U.S.

September 27, 2013

Military Intelligence – this week in history September 27

Tags:
Ruth Quinn, Staff Historian
USAICoE Command History Office
Courtesy Photo
The SIS used this analog of the Japanese Purple machine to decipher Japanese diplomatic messages in 1940.

Purple is much more than color for signals intelligence

The SIS used this analog of the Japanese Purple machine to decipher Japanese diplomatic messages in 1940.

Sept. 25, 1940
By the spring of 1939, William Friedman’s teams of cryptologists had already achieved partial success with the Italian and German code-systems and the Japanese army systems. At the same time, the Navy had managed to break a number of the Japanese naval codes. But the biggest puzzle of all was the Japanese diplomatic cipher system, used by the Foreign Office in Tokyo for its most secret communications with its ambassadors serving abroad. This system was nick-named “Purple” – and it became the most legendary encipherment system in the history of cryptography prior to the computer age.

The first few Purple messages were intercepted in 1937. It took awhile for there to be enough traffic for the Signals Intelligence Service, or SIS, to even attempt to decipher them. The team expected the solution to follow the same pattern as the Enigma machine that the Germans had been using since the 1920s. They were quickly dismayed to find that the Japanese had implemented numerous ingenious adaptations and improvements to the Enigma, multiplying the difficulties of deciphering its code.

Ronald Clark, in his book “The Man Who Broke Purple,” explains the difficulty faced by Friedman and his expert team of SIS cryptologists:
“The first step in what seemed to be the impossible task of decipherment lay in collecting a certain minimum of traffic sent on one day – or, at least, sent with the same keys in operation, which was initially the same thing. The next step was to decide which permutation and combination of wiring could have been used to produce such a set of enciphered messages. If the decision was correct all messages sent on that particular day could be deciphered to produce intelligible plaintext. If not, not; and for month after month it was always not.”

It was slow, painstaking work. But gradually, the SIS team built up bits and pieces of deciphered traffic. In February 1939, General Mauborgne, the Chief Signal Officer, ordered Friedman to drop all of his other duties, and he and his staff concentrated solely on solving Purple. It became Friedman’s consuming passion, conducted in total secrecy, for an excruciating eighteen months.

In August 1940, the SIS had a breakthrough, which allowed them to build a mock-up of the Japanese encryption machine – called an analog. The Purple analog allowed the SIS analysts, to produce its first major, ungarbled, translated “solutions” of two PURPLE messages on Sept. 25, 1940. Ironically, this major success occurred just two days before Germany, Italy and Japan signed in Berlin the Tripartite Pact pledging all 3 of them to mutual support, an event which led to an unexpected, but useful, cascade of Purple messages. The Americans not only had the ability to read the diplomatic traffic, they had plenty of it to read.

Of course, there were plenty of issues that slowed down the process, such as the physical delay in passing encrypted intercepts from the field to the cryptographers in Washington, the small number of trained analysts handling a huge volume of traffic, and finding people who could translate accurately the deciphered messages. In spite of these obstacles, William Friedman had handed his government a tool which would change the course of history. As Clark writes, “By the autumn of 1940 there was available for the State Department, and for the Chiefs of Staff, a continuing flow of top secret information from Tokyo in which the Japanese leaders outlined their plans for the future and the strategy and tactics with which they were to be carried out.”




All of this week's top headlines to your email every Friday.


 
 

 
Maranda Flynn

Sergeant Major of the Army talks Fort Huachuca’s leadership, success in Army’s future

Maranda Flynn Sgt. Maj. of the Army Raymond Chandler III speaks to Fort Huachuca, Ariz. Soldiers about battle buddy safety during a town hall meeting held at Cochise Theater, Aug. 20. As force reduction kicks into gear, Soldier...
 
 

Celebrating Women’s Equality Day — 2014

The Nation’s Annual Observance of Women’s Equality Day commemorates the addition of the 19th Amendment to the Constitution, which guarantees women the right to vote. This victory moved our Nation forward on the path towards equal civil and political rights for all Americans. The roles of women in the Army have changed dramatically since 1775....
 
 
Courtesy of the International Military Student Office

IMSO plays integral part in international students’ lives here

Courtesy of the International Military Student Office International military students meet U.S. Representative Ron Barber while taking a week-long trip to Washington D.C. The trip was organized by the International Military Stu...
 

 

New 35Q course offered at Fort Huachuca NCOA

The new Cryptologic Network Warfare Analyst Advanced Leader Course, ALC, resumed its second cycle of classes this month at the Noncommissioned Officer Academy, NCOA. The 288-hour, small group-led ALC prepares noncommissioned officers to assume supervisory roles in cyber analysis and operation elements. Upon completion, Soldiers should be able to apply critical thinking while supervising and...
 
 
Lisa Ferdinando

Army focuses on good energy stewardship to protect mission

Lisa Ferdinando Katherine Hammack, assistant secretary of the Army for Installations, Energy and Environment, speaks at a panel discussion in Washington, D.C., April 10, 2013. WASHINGTON — The Army is focused on being a good ...
 
 

Under Secretary challenges Army senior leaders to revamp Civilian career management

ARLINGTON, Va. — During a two-day session at the Pentagon last month, approximately 30 members of the Senior Executive Service, or SES, gathered to discuss how to improve Civilian career development. Army Under Secretary Brad Carson hosted the event, which was meant to help shape policy changes regarding how the Army hires, trains, develops and...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>


Directory powered by Business Directory Plugin