Posted on 05/31/2007 7:32:57 AM PDT by doug from upland
DFU NOTE: if the New York Times had the same editors and owners they now have, this would have been an example of their reporting during WW II.
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PREVIOUS STORIES --
1 - NAVAJO CODE TALKERS
2 - MANHATTAN PROJECT
3 - OPERATION OVERLORD
4 - PLOT TO ASSASSINATE HITLER
5 - TOKYO BOMBING RAID
6 - ANNE FRANK
June 1, 1942 ("What if" in History - No. 7) NAVY BREAKS JAPANESE CODE
In an exclusive interview, a source from the Department of War has told the NEW YORK TIMES that American cryptanalysts have broken the Japanese code. In the late 1930s, Army Signal Intelligence Service(SIS) cryptanalysts succeeding in breaking the Purple code, also designated AN-1, which was the principal cipher Japan used to send diplomatic messages. (While the terms code and cipher are often used interchangeably, a code is a substitution of one character or string of characters for another; reading a cipher, however, usually requires application of some kind of mathematical operation specified by a cipher key; a simple cipher, for example, might require the decoder to subtract a designated value from a string of numbers to arrive at the true string of numbers that encodes a letter, word, or phrase.)
On June 1, 1939, the Japanese introduced what American cryptanalysts called JN–25. JN means simply Japanese Navy, and JN–25, consisting eventually of about 33,000 words, phrases, and letters, was the primary code the Japanese used to send military, as opposed to diplomatic, messages.
After Pearl Harbor, U.S. intelligence efforts focused on cracking JN–25. Leading the effort, code-named Magic, was the U.S. Navy's Combat Intelligence Unit, called OP–20–G and consisting of 738 naval personnel. The unit, housed in the basement of the 14th Naval District Administration at Pearl Harbor, was under the command of Commodore John Rochefort, who combined fluency in Japanese with single-minded dedication to the task.
Using complex mathematical analysis, IBM punch-card tabulating machines, and a cipher machine, Friedman had developed the ECM Mark III, the unit was able to crack most of the code by January 1942. The blanket name given to any information gained by deciphering JN–25 was Ultra, a word borrowed from British codebreaking efforts and stamped at the top of all deciphered messages.
The Combat Intelligence Unit worked tirelessly, but the unit had some help from the Japanese themselves. For example, messages, primarily radio transmissions, often began with such stylized phrases as "I have the honor to inform your excellency" and with the names of ships, locations, commanders, the time and date, and similar repeated information that could be easily verified; many referred to military and other officials by formal, stylized titles. These weaknesses, combined with the fact that the Japanese introduced changes to the code only every three to six months, gave American cryptanalysts a toehold into the code.
Soon they were able to read the code, which consisted of strings of five digits. Thus, for example, the string 97850 meant submarine, although because JN–25 was really a cipher, the cryptanalyst had to subtract a value from the string of digits to arrive at the correct meaning. Making this task somewhat easier for Americans, the Japanese changed their cipher key infrequently.
Armed with the ability to read Japanese operational messages, the U.S. Navy may be in a better position to turn back the Japanese advance in the Pacific. Our source has informed us that in April, decrypted messages revealed that Japanese forces were preparing for an assault on Port Moresby, an Australian base in New Guinea, in early May. In response, U.S. Admiral Chester Nimitz moved his fleet into the Coral Sea between New Guinea and Australia. While the ensuing two-day Battle of Coral Sea was considered a draw, U.S. forces inflicted enough damage on the Japanese navy to force it to withdraw, giving the United States and Australia time to reinforce Allied defenses in New Guinea.
Within days, the Navy is anticipating a battle that has been given the name the Battle of Midway. The plan of Japanese commander Admiral Isoroku Yamamoto is to assemble an aircraft carrier task force, launch a diversionary raid off the Aleutian Islands, and lure the U.S. Navy to Midway Island and into a decisive battle. The Japanese hope to destroy what remains of the American fleet after Pearl Harbor, an attack we brought on ourselves.
From decrypted messages, U.S. naval commanders know the general outlines of the plan, even the timetable. The messages, however, did not say where the Japanese intended to strike; the target was simply designated "AF."
It was Rochefort who proposed a ruse to determine what AF stood for. Suspecting that it was Midway Island, he arranged for American forces on the island to send out a radio message saying that they were running short of fresh water. Rochefort and his group waited anxiously to see if Japan would take the bait. Finally, codebreakers intercepted a Japanese message: AF was running short of fresh water.
Knowing that the assault is to come at Midway, the U.S. Navy will be ready. U.S. pilots hope to sink all four Japanese aircraft carriers in Yamamoto's task force and turn the tide in the Pacific.
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REAL HISTORICAL NOTE:
In a breach of wartime security, the Chicago Tribune actually did publish a story revealing that the navy had known about Japanese intentions in advance, in effect revealing that JN–25 had been broken. The Japanese never found out about the article.
Good thing Al Gore hadn’t invented the Internet yet.
Ping
I have no doubt that is what they'd print.
Another great one, and informative too - I didn't know a lot about breaking the Japanese codes during the Pacific campaign.
Brilliant!
I also have learned quite a lot doing this series.
i saw that after the fact...
last July when we Freeped the NY Slimes building (along with Firebrand and a few other Freepers)after they exposed a bunch more classified documents, some were wearing shirts which had the front page what the NY Times would look like if the invasion on D-Day were held today...it was in the spirit of my post and your thread...the shirts were great!!
Breaking the Japanese code offends their cultural sensibilities and self-esteem and we call on President Roosevelt to disband all such activities. Any attempts at stopping Japanese money laundering in Hawaii and elsewhere must also be stopped, because the Japanese self defense forces need to protect their homeland. Although we are at war we cannot debase ourselves with such activities. It is un-american to sniff at others mail and watch their money like greedy hawks.
Any torture, no matter how slight, on Japanese non-uniformed, non-idenified saboteurs must stop. We must not do anything to disturb their cultural awareness and give full Geneva Right to these insurgents even though they have not follow the protocol. It is only American.
Any observing of their shrines, in this country, must also be stopped for the same reason.
bump
Well, yes, but they would only do that because the invasion plan is hopeless and thousands of lives will be lost.
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