Magic (cryptography)
In World War II, Magic was the US codename for intelligence derived from the cryptanalysis of Purple, a Japanese foreign office cipher.
History
When Purple was broken by the US Army's beginning of the second week in December 1941, that was the last time anyone on the list saw that particular decrypt.
Decryption Process
There were several prior steps needed before any decrypt was ready for distribution:
- First, it had to be intercepted. The Japanese Foreign Office used both wireless transmission and cables to communicate with its off shore units. Wireless transmission was intercepted (if it was possible to do so) and any of several listening stations (Hawaii, Guam, Bainbridge Island in Washington State, etc) and the raw cypher groups forwarded to Washington. Eventually, there were decryption stations (ie, including a copy of the Army's Purple machine) in the Philippines as well. Cable traffic was (for many years before late 1941) collected at cable company offices by a military officer who made copies and started them to Washington. Cable traffic in Hawaii was not interecepted (illegality remember) until David Sarnoff of RCA agreed to allow it during a visit to Hawaii the first week of December 1941. At one point, intercepts were being mailed to (Army or Navy) Intelligence from the field!
- Second, the raw intercept had to be decyphered. This was done by either the Army or the Navy (depending on the day) and, because of the nature of the cypher and the break into it, was usually successful.
- Third, having obtained the plaintext, in Latin letters (!), it was translated. Because the Navy had more Japanese speaking officers, much of the translating burden fell onto the Navy. And because Japanese is a difficult language, leaving much meaning to context, effective translation required not only fluent Japanese, but considerable knowledge of the context within which the message was sent.
- Fourth, the now translated decrypt had to be evaluated for its intelligence content. For example, is the ostensible content of the message meaningful? If it is, for instance, part of a power contest within the Foreign Office or some other part of the Japanese government, its meaning/implications would be quite different than if it were a simple informational or instructional message to an Embassy. Or, might it be another message in a series whose meaning, taken together, is more than the meaning of any individual message. Thus, the forteenth message to an Embassy instructing that Embassy to instruct Japanese merchant ships calling at that country to return to home waters before, say, the end of November would be more significant than a single such message meant for a single ship or port. Only after having evaluated a translated decrypt for its intelligence value could anyone decide whether it deserved to be distributed.
In the period before the attack on Pearl Harbor, the material was handled awkwardly and inefficiently, and was distributed even more awkwardly. Nevertheless, the extraordinary experience of reading a foreign government's most closely held communications, sometimes even before the intended recipient, was astonishing. It was so astonishing, that someone (possibly President Roosevelt) called it magic. The name stuck.
One aspect of Magic remains controversial to this day - the amount of involvement, if any, the intercepts played in the issuing of United States Executive Order 9066, which lead to the internment of Japanese Americans living on the US West Coast. Those defending the internment, most notably author Michelle Malkin, point to Magic intercepts as being justification for the internment. The rationale for this is that several Magic intercepts discuss the development of a spy ring among Japanese Americans by the Japanese consulates, showing that the Japanese American community was an espionage risk.
Those in opposition point out that:
- the commanding officer who executed the internment, Lt. Gen. J. L. DeWitt, was not on the Magic intercept list,
- his superior, Secretary of War Henry Stimson, was on the intercept list, and
- Stimson requested justification for the internment from DeWitt (if Magic intercepts provided justification, why ask DeWitt for further justification?).
The issue has been inflamed recently due to the release of Malkin's recent book, In Defense Of Internment, in which the Magic intercepts play a major role in the defense of her thesis.
