Japan Broke U.S. Code Before Pearl Harbor, Researcher Finds

Paul Krumviede pwk at acm.org
Sun Dec 9 01:50:11 EST 2001

while not really cryptography related, i'd suggest a reading of the chapter
"prologue to pearl harbor" of herbert bix's "hirohito and the making of
modern japan" before taking seriously anything other than the finding that 
japanese may have broken one (or more) american cipher.

comments on japanese surprise at the (long-standing) american insistence
on withdrawal from china seem akin to japanese hopes in mid-1945 that
somehow the soviets could be persuaded to intervene on their behalf
to avoid surrendering... (on this subject, richard frank's "downfall" has
some interesting analysis of what the americans were learning from the
various japanese ciphers in 1945, including the diplomatic and military


--On Friday, 07 December, 2001 11:09 -0500 "R. A. Hettinga" 
<rahettinga at earthlink.net> wrote:

> http://www.latimes.com/templates/misc/printstory.jsp?slug=la%2D120701codes
> http://www.latimes.com/news/nationworld/world/la-120701codes.story
> Japan Broke U.S. Code Before Pearl Harbor, Researcher Finds
> Asia: Discovery is based on papers unearthed in Tokyo. They show attack
> may have been prompted by belief that Washington had decided on war. By
> Times Staff Writer
> December 7 2001
> TOKYO -- Toshihiro Minohara made a startling discovery while digging
> through the U.S. National Archives in College Park, Md., last summer.
> While researching secret codes used prior to the attack on Pearl Harbor
> 60 years ago, the young Japanese American professor stumbled upon a
> document, declassified by the CIA about five years ago, that proved that
> Tokyo had succeeded in breaking the U.S. and British diplomatic codes. A
> few microfilmed documents, showing the Japanese translations of the
> telegrams, were attached.
> Minohara knew he was on to something important: For decades it was widely
> believed that Japan, then a developing country with a fierce rivalry
> between its army and navy, hadn't been up to measure when it came to
> code-breaking, particularly the documents of the Americans.
> "We are so . . . arrogant," said Donald Goldstein, a professor at the
> University of Pittsburgh and co-author of "At Dawn We Slept: The Untold
> Story of Pearl Harbor." "It's very possible they could have broken our
> code, so why shouldn't they have?"
> Research in Tokyo Confirms Findings
> Further research by a colleague in Japan confirmed the findings--and may
> shed light on the mind-set that caused Japan's last holdouts for peace to
> opt for war just weeks before the attack, Minohara said this week.
> When Minohara sent fellow Kobe University teacher Satoshi Hattori to check
> Japan's diplomatic archives in Tokyo, he wasn't optimistic: Most
> top-secret documents were burned after being read in wartime Japan. Those
> that remained were confiscated by the U.S. during the occupation that
> followed Japan's 1945 defeat; they are now housed in U.S. archives.
> But Hattori unearthed a folder marked "Special Documents," containing 34
> communiques that would have been easy to overlook--and apparently have
> been by other Japanese researchers numerous times. They are simple typed
> pages, written primarily in English, of U.S. and British diplomatic
> discussions and telegrams, many from U.S. Secretary of State Cordell Hull
> to various U.S. ambassadors.
> The contents of the documents have long been known to historians the world
> over, and some even pop up on the Internet. But their appearance in the
> Japanese archives reveals that Tokyo knew what was going on in Washington
> in the weeks before Dec. 7, 1941, when the Japanese attacked Pearl Harbor,
> killing more than 2,000 people.
> Minohara says his findings may shed light on why the few doves in the
> Japanese Cabinet--in particular, Foreign Minister Shigenori Togo--dropped
> their opposition to war.
> Japan Stunned by Hard-Line U.S. Edict
> The U.S., alarmed by the march of Japan's Imperial Army through Asia, had
> imposed an oil embargo on the nation and told it to get out of China,
> among other things. Togo had sent a conciliatory rebuttal, known as the
> "Five Points Plan," offering some concessions and seeking to continue
> discussions.
> Japan knew from the decoded cables that the U.S. had been seriously
> considering some of the compromises. But on Nov. 26, 1941, the Americans
> stunned Japan with a hard-line edict essentially ordering Tokyo's troops
> to get out of China and Indochina or face the consequences. This
> apparently convinced even Togo that the U.S. had decided on war.
> Many historians have speculated that President Franklin D. Roosevelt was
> looking for an excuse to get into the war in Europe; they posit that he
> knew Japan would attack but thought the target might be American forces in
> the Philippines or instead perhaps Malaya, then a British colony, which
> would prompt the U.S. to come to the aid of its ally.
> The newly revealed documents raise an interesting question, Minohara says.
> Had the American side accepted the compromises it was considering--lifting
> the oil embargo for three months, permitting Japanese troops to remain in
> Indochina and continuing discussions on Japan's occupation of
> Manchuria--would Tokyo have still gone through with the surprise attack on
> Pearl Harbor?
> Japan's war vessels had long before set sail for the Pacific, and the
> command "Climb Mt. Itaka" meant for Japanese troops to go forward with the
> attack on Pearl Harbor; but there was also a lesser-known command, "Climb
> Mt. Tsukuba," which meant return.
> "The big question is why the U.S. dropped the offer," says Minohara, 30,
> who did undergraduate work at UC Davis before moving to Japan for graduate
> school at Kobe University, where he now teaches.
> Togo wrote in his memoirs that, when he read the edict from the U.S., "I
> was shocked to the point of dizziness. At this point, we had no choice but
> to take action."
> Historians often wondered why he was so shocked. Minohara says Togo's
> raised expectations that a deal was in the offing led to his anger.
> Thomas G. Mahnken, a strategy professor at the U.S. Naval War College in
> Rhode Island who recently completed a book on U.S. intelligence on Japan
> in the years before World War II, says the knowledge that Japan was
> breaking the codes is "significant."
> Then again, Mahnken notes, the U.S. diplomatic telegrams "were not
> tremendously sophisticated," and a number of countries had even broken
> those used by military attaches.
> Neither Japan nor the U.S. had broken the other's military codes prior to
> Pearl Harbor, Minohara says.
> Japanese historians often claim that the U.S. misinterpreted some of the
> country's telegrams--for instance, that Togo's "Five Points Plan" was
> translated as a "final offer" when Togo never said that.
> Minohara says the Japanese "were doing the same thing. Even though there
> was no error in the translations, they were still misinterpreting the
> U.S.' intentions."
> For information about reprinting this article, go to
> http://www.lats.com/rights --
> -----------------
> R. A. Hettinga <mailto: rah at ibuc.com>
> The Internet Bearer Underwriting Corporation <http://www.ibuc.com/>
> 44 Farquhar Street, Boston, MA 02131 USA
> "... however it may deserve respect for its usefulness and antiquity,
> [predicting the end of the world] has not been found agreeable to
> experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'
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