The Letters from General Marshall to Governor Dewey, 25 and 27 September 1944
The Marshall-Dewey correspondence is so important in cryptologic history that I feel the whole of it should be included even in this brief history. When the letter was written, it was, of course, TOP SECRET and it was only under great pressure from certain members of the Joint Congressional Committee that General Marshall revealed its contents. Thus, it came into the public domain not only on the very day that General Marshall was forced to place it in evidence – its publication caused a great sensation in the newspapers – but also when the forty volumes of the hearings of that committee were published and put on sale by the Superintendent of Documents of the Government Printing Office. The disclosure of the contents of the Marshall-Dewey correspondence was indeed such a sensation that Life printed the whole of it in its issue of 17 December 1945, with the following introduction:
MARSHALL-DEWEY LETTERS
General Told Candidate We Had Broken Jap Code
During the 1944 election campaign General George C. Marshall wrote two letters to Republican candidate Thomas E. Dewey, telling him that Army cryptographers had broken the Japanese "ultra" code. This fact was first revealed in a story by Life Editor John Chamberlain, which appeared in Life, Sept. 24. Marshall's purpose, Chamberlain wrote, was to forestall Dewey's revelation of that fact in a possible attack on the Roosevelt administration's Japanese policy before Pearl Harbor. The actual text of the letters emained secret until last week, when General Marshall appeared before the Congressional committee investigating Pearl Harbor and made the letters public. They appear below.
When he had finished reading the first two paragraphs of the first letter, Governor Dewey stopped because, as the Chamberlain article reported, "the letter might possibly contain material which had already come from other sources, and that anyway, a candidate for President was in no position to make blind promises." General Marshall sent the letter back again with an introduction which relieved the governor of binding conditions. This time Dewey read the letter and after much thought and discussion decided not to make use during the campaign of any information he previously had.
First Letter
TOP SECRET
(FOR MR. DEWEY'S EYES ONLY)
25 September 1944
My Dear Governor:
I am writing you without the knowledge of any other person except Admiral King (who concurs) because we are approaching a grave dilemma in the political reactions of Congress regarding Pearl Harbor.
What I have to tell you below is of such a highly secret nature that I feel compelled to ask you either to accept it on the basis of your not communicating its contents to any other person and returning the letter or not reading it any further and returning the letter to the bearer.
I should have preferred to talk to you in person but I could not devise a method that would not be subject to press and radio reactions as to why the Chief of Staff of the Army would be seeking an interview with you at this particular moment. Therefore, I have turned to the method of this letter, to be delivered by hand to you by Colonel Carter Clarke, who incidentally has charge of the most secret documents of the War and Navy Departments.
In brief, the military dilemma resulting from Congressional political battles of the political campaign is this:
The most vital evidence in the Pearl Harbor matter consists of our intercepts of the Japanese diplomatic communications. Over a period of years our cryptograph people analyzed the character of the machine the Japanese were using for encoding their diplomatic messages. Based on this, a corresponding machine was built by us which deciphers their messages.
Therefore, we possessed a wealth of information regarding their moves in the Pacific, which in turn was furnished the State Department – rather than, as is popularly supposed, the State Department providing us with information – but which unfortunately made no reference whatever to intentions toward Hawaii until the last message before Dec. 7, which did not reach our hands until the following day, Dec. 8.
Now the point to the present dilemma is that we have gone ahead with this business of deciphering their codes until we possess other codes, German as well as Japanese, but our main basis of information regarding Hitler's intentions in Europe is obtained from Baron Oshima's message from Berlin reporting his interviews with Hitler and other officials to the Japanese Government. These are still in the codes involved in the Pearl Harbor events.
To explain further the critical nature of this setup which would be wiped out almost in an instant if the least suspicion were aroused regarding it, the Battle of the Coral Sea was based on deciphered messages and therefore our ships were in the right place at the right time. Further, we were able to concentrate our limited forces to meet their advances on Midway when otherwise we almost certainly would have been some 3,000 miles out of place.[46]
We had full information of the strength of their forces in that advance and also of the smaller force directed against the Aleutians which finally landed troops on Attu and Kiska.
Operations in the Pacific are largely guided by the information we obtain of Japanese deployments. We know their strength in various garrisons, the rations and other stores continuing available to them and what is of vast importance, we check their fleet movements and the movements of their convoys.
The heavy losses reported from time to time which they sustain by reason of our submarine action largely results from the fact that we know the sailing dates and the routes of their convoys and can notify out submarines to lie in wait at the proper point.
The current raids by Admiral Halsey's carrier forces on Japanese shipping in Manila Bay and elsewhere were largely based in timing on the known movements on Japanese convoys, two of which were caught, as anticipated, in his destructive attacks.
You will understand from the foregoing the utter tragic consequences if the present political debates regarding Pearl Harbor disclose to the enemy, German or Jap, any suspicion of the vital sources of information we now possess.
The Roberts report on Pearl Harbor had to have withdrawn from it all reference to this highly secret matter, therefore in portions it necessarily appeared incomplete. The same reason which dictated that course is even more important today because our sources have been greatly elaborated.
As a further example of the delicacy of the situation, some of Donovan's people (the OSS), without telling us, instituted a secret search of the Japanese Embassy offices in Portugal. As a result the entire military attaché Japanese code all over the world was changed, and though this occurred over a year ago, we have not yet been able to break the new code and have thus lost this invaluable information source, particularly regarding the European situation.
A recent speech in Congress by Representative Harness would clearly suggest to the Japanese that we have been reading their codes though Mr. Harness and the American public would probably not draw any such conclusion.
The conduct of General Eisenhower's campaign and of all operations in the Pacific are closely related in conception and timing to the information we secretly obtain through these intercepted codes. They contribute greatly to the victory and tremendously to the saving of American lives, both in the conduct of current operations and in looking toward the early termination of the war.
I am presenting this matter to you, for your secret information, in the hope that you will see your way clear to avoid the tragic results with which we are now threatened in the present political campaign. I might add that the recent action of Congress in requiring Army and Navy investigations for action before certain dates has compelled me to bring back the corps commander, General Gerow, whose troops are fighting at Trier, to testify here while the Germans are counterattacking his forces there. This, however, is a very minor matter compared to the loss of our code information.[47]
Please return this letter by bearer. I will hold it in my secret file subject to your reference should you so desire.
Faithfully yours, G.C. Marshall
Second Letter
TOP SECRET
(FOR MR. DEWEY'S EYES ONLY)
27 September 1944
My Dear Governor:
Colonel Clarke, my messenger to you of yesterday, Sept. 26, has reported the result of his delivery of my letter dated Sept. 25. As I understand him you (A) were unwilling to commit yourself to any agreement regarding "not communicating its contents to any other person" in view of the fact that you felt you already knew certain of the things probably already referred to in the letter, as suggested to you by seeing the word "cryptograph," and (B) you could not feel that such a letter as this to a Presidential candidate could have been addressed to you by an officer in my position without the knowledge of the President.
As to (A) above I am quite willing to have you read what comes hereafter with the understanding that you are bound not to communicate to any other person any portions on which you do not now have or later receive factual information from some other source than myself. As to (B) above you have my word that neither the Secretary of War nor the President has any intimation whatsoever that such a letter has been addressed to you or that the preparation or sending of such a communication was being considered.
I assure you that the only persons who saw or know of the existence of either this letter or my letter to you dated Sept. 25 are Admiral King, seven key officers responsible for security of military communications, and my secretary who typed these letters.
I am trying my best to make plain to you that this letter is being addressed to you solely on my initiative, Admiral King having been consulted only after the letter was drafted, and I am persisting in the matter because the military hazards involved are so serious that I feel some action is necessary to protect the interests of our armed forces.
(The second letter then repeated substantially the text of the first letter except for the first two paragraphs.)
Life failed to note that the last two sentences in the penultimate paragraph of the "First Letter" were omitted from that paragraph in the "Second Letter," but there is no explanation for the omission.[48] Perhaps it was simply for the sake of brevity, but this seems improbable.
In my first lecture I called attention to the fact that the account given in the Time article gives credit to Army cryptanalysts for providing the secret intelligence "which enabled our navy to win such spectacular battles as those of the Coral Sea and Midway, and to waylay Japanese convoys," whereas the credit for the communications intelligence which enabled our navy to win those battles was produced by Navy cryptanalysts. One cannot blame the editors of Time for making such a bad error because the source of the error can be traced directly to General Marshall's letter itself. Several years ago I asked my friend Colonel Clarke, who, you will recall, carried General Marshall's letter to Governor Dewey, how such an error had crept into General Marshall's letter and was told that the letter that had been prepared for General Marshall's signature did not meet with the General's wholehearted approval and that the General himself had modified it. Perhaps that is how the error to which I have referred crept into it. One could hardly expect General Marshall to be entirely familiar with the technical cryptanalytic details involved in what he wanted to tell Governor Dewey, nor should one criticize him for not being able, in his very busy days and under very heavy pressure of events, to bear in mind or even to know about the differences between the enemy systems worked upon by the respective and separate Army and Navy cryptanalytic organizations. It is of course possible, indeed it may be, that in the cases of certain important naval operations valuable COMINT came from messages read by Army cryptanalysts, and this may be what confused General Marshall in implying that all the credit belonged to them because of their solution of the Japanese highest-level diplomatic cryptosystems, the one that used the so called "Purple Code," which wasn't a code but a cipher machine.
Since the period during which the disclosures of the joint congressional investigation were made, disclosures which were disastrous so far as the important accomplishments of the two services before and after the Pearl Harbor attack in the field of communications intelligence, much has been written and is now in the public domain regarding those accomplishments, but fortunately no technical details of significance have been disclosed.
[43] While I have no recollection of the Boston business. I shall never forget the Lisbon incident. – W.F.F.
[44] "A few days later..." But note that the first letter is dated 25 September 1944, the second, 27 September. It is possible that Colonel Clarke was unable to deliver the letter, but my recollection is that he did deliver it the very next day.-W.F.F.
[45] So far as I am aware it has neither been ascertained nor disclosed, if known, who gave Governor Dewey the information. But it is a fact that as a patriotic citizen, he acceded to General Marshall's request – he made no use whatever of the vital secret information during the campaign or after it.Time's account specifically states that Dewey "held his tongue. The War Department's most valuable secret was kept out of the campaign". I know this to be true.-W.F.F.
[46] In regard to this and the succeeding four paragraphs, see my comment below (p.129).
[47] The last two sentences in this paragraph were omitted from the Second Letter. See footnote 6.
[48] The sentence beginning "I might add. . ." and the one beginning "This, however is. . ." were omitted.