The 12/7-9/11 Treadmill and Beyond
February 12 2009
last edited 3/26
Throughout November 1941, as US-Japanese negotiations were secretly segueing into war maneuvers, the Japanese Navy mobilized to strike out across the Pacific at British, Dutch, and American interests. The last was tasked to a mighty force that had been assembled in secrecy at the 4-mile-wide hammer-head shaped Hitokappu Bay in the southern Kuril Islands (just north of Japan’s Hokkaido Island). By the middle of the month, would have been bustling with the “mobile striking force,” or Kido Butai, under the command of Admiral Chuichi Nagumo in his flagship Akagi; he was backed by 2 battleships, 2 heavy cruisers, 9 destroyers, 3 submarines, 8 train vessels, and, most tellingly, 6 aircraft carriers with about 360 combat-ready aircraft.
On the 25th, Fleet Admiral Yamamoto issued to Nagumi the fateful Combined Fleet Operations Order No. 5, ordering the force to set off for its intended target: - Pearl Harbor, Hawaii, and the bulk of the US Pacific Fleet moored there. The source from which I take this is the Joint Congressional Committee on Pearl Harbor, part 2 of their final report, published in 1946 . Their telling reads as such:
”(a) The task force, keeping its movements strictly secret and maintaining close guard against submarines and aircraft, shall advance into Hawaiian waters and upon the very opening of hostilities, shall attack the main force of the United States Fleet in Hawaii and deal it a mortal blow. The first air raid is planned for dawn of X-day (exact date to be given by later order).
Upon completion of the air raid the task force, keeping close coordination and guarding against enemy counterattack, shall speedily leave the enemy waters and then return to Japan.
(b) Should it appear certain that Japanese-American negotiations will reach an amicable settlement prior to the commencement of hostile action, all the forces of the combined fleet are to be ordered to reassemble and return to their bases.
(c) The task force shall leave Hitokappu Bay on the morning of November 26 and advance to 42° N. And 170° E. (standing-by position) on the afternoon of December 4, Japan time, and speedily complete refueling. “
Clearly this order was crucial; it mentioned the target, the nature and location of the sneak attack, and the approximate date and time of day it would occur, just over two weeks later. If such information could have become available at that time to the US or to an ally inclined to share, the surprise could have been seen and pre-empted, or at least mitigated with some kind of proportional defense. None of this happened, of course, and the Kido Butai achieved total local surprise, which one may be tempted to accept as de facto evidence that the order remained hidden from American eyes at the time.
Such temptation should be resisted.
illustration using the given coordinates for stand-by position. This isn't quite right, as illustrated by the huge distance to travel the last leg. This probably means they modified the plan later, or had a further code in which one location actually mans another. A better map from Japanese sources can be seen at this page, and was used to make the more accurate and useful graphic below.
The Japanese Navy ordered the destruction of much of their records at war’s end, all copies of this order apparently being among the lost. Therefore, the Committee’s source for the wording they presented as evidence in 1946 would have to come from some other record(s) – hard copies that escaped the destruction order and fell into US hands, the memories of people who had written, read, or recieved the orders, or perhaps ‘our own copies,’ radio intercepts received by the US or an ally at the time but (presumably) decoded later.
In fact, the source the Committee cites is, essentially, anything but the third option. The order to sail is attributed to “Committee exhibit no. 8,” cited extensively throughout part two of their report when referencing Japanese plans or communications. Therein they explain:
“The chief sources of information concerning the attack are translations of captured Japanese documents, interrogations of prisoners of war, and reports submitted by general headquarters, supreme commander for the Allied Powers, comprising questionnaires filled out since VJ-day by former members of the Japanese naval high command. See committee exhibits Nos. 8, 8A, 8B, 8O, and 8D.” So it would seem that, even four years after the attack and the penetration of all Japanese codes, fuzzy memory and the odd scrap of paper was the best the Committee had access to. Apparently, we never got a copy of our own to decode and it was just lost into the ether. Admiral Edwin Layton concluded, after searching the available intercepts at the National Archive, “we evidently did not pick up Yamamoto’s 25 November sailing message” at all.  Note the judicious use of “evidently.”
The Pacific Fleet’s top intelligence officer at Pearl Harbor at that time, Layton published his own investigation at the end of his life, in the mid-1980s. Having found nothing of it in our archives, his source for the order to sail was “a reconstruction of events obtained from [the striking force’s] surviving commanders in 1945.” In particular, he cited the recollections of Capt. Mitsuo Fuchida, lead pilot of the actual air raid. This version is essentially the same as the above, with the exception of an “evening rendezvous” to refuel on Dec 3 Tokyo, not Hawaii time, and located at 40°N 170°E, two degrees south of the Committee’s findings. 
An Army Military History office document released in 1953 provides a whole string of communications surrounding the Kido Butai’s formation and intent, dating Nov 5 to Dec 2. While previous communications outlining the attack plan for Hawaii are recounted in great detail here, Yamamoto’s decisive Nov 25 order is provided only in a “general outline,” altering the standing-by position (from 165° to 170°) and ordering departure. Again, this document notes that “since all copies of these orders were destroyed prior to the end of the war, they have been reconstructed from personal notes and memory.” 
There is much debate among American researchers and little conclusive resolution as to how readable that code was to American cryptanalysts on December 7. The general mainstream consensus is that it was completely or essentially unreadable in the last days, as well as at the time of this pivotal order. The question of the code’s overall opacity as of November 25 1941 is one with no conclusive answer [hint - it was LESS likely to be readable on X-Day, and there are other nations whose own progress is uncertain]. The topic is shrouded in curiously dense secrecy and confusion (at least on my part), and will be the subject of a further post, or posts, after I’ve completed more research.
 Investigation of the Pearl Harbor Attack. Report of the Joint Committee on the Investigation of the Pearl Harbor Attack. July 20 1946. Part II. Page 56. online - backup
 Ibid. Page 53.
 Layton, Edwin T. with Roger Pineau and John Costello "And I Was There": Pearl Harbor And Midway - Breaking the Secrets. William Morrow & Co. December 1985. Page 207.
 Ibid. Page 207.
 Japanese Monograph No. 97. PEARL HARBOR OPERATIONS: General Outline of Orders and Plans. Prepared by Military History Section Headquarters, Army Forces Far East. Distributed by Office of the Chief of Military History
Department of the Army. 19 February 1953. link