by DAVID KAHN
Deep in the Bougainville jungle, Yamamoto’s devoted aide found his admiral’s charred corpse still in its seat, its chin on a samurai sword. The body was extricated with care and solemnly burned. On May 21 a Japanese newscaster announced, in tones heavy with sorrow, that Yamamoto, “while directing general strategy on the front line in April of this year, engaged in combat with the enemy and met gallant death in a war plane.” Toward the end of the communiqué his voice became choked, as if through tears. As Layton and Nimitz had foreseen, Yamamoto’s death stunned the entire nation. On June 5, his ashes were interred with great pomp in Tokyo’s Hibiya Park in the presence of the government and an immense and silent crowd. The death of the great popular hero disheartened Japanese soldiers, sailors, and civilians. “There was only one Yamamoto, and no one is able to replace him,” said the man who succeeded him. “His loss is an insupportable blow to us.” Cryptanalysis had given America the equivalent of a major victory.
In forwarding a report of the Yamamoto operation to Admiral King, Nimitz noted that it took place “on a particularly high plane of secrecy” and recommended that “no publicity of any kind should be given this action.” The main reason was to keep Japan’s curiosity from being drawn to how the United States knew that Yamamoto was in a certain airplane. A secondary reason was that Lanphier’s brother was a Japanese prisoner of war and reprisals were feared. Thus Americans only learned of the admiral’s death from news stories based on the Japanese newscast.
Many wondered how it had happened. No major combat activity extensive enough to cause such a death had occurred in April. The armed forces, following Nimitz’ advice, blankly disclaimed any knowledge of the incident. One rumor speculated that Yamamoto had died in an air accident, another that he had committed hara-kiri because of increasing Allied successes. But the real story filtered into wider and wider circles, until soon much of official Washington was whispering at cocktail parties and dinners—probably right under those ubiquitous “The walls have ears” posters—about how cryptanalysis killed Yamamoto. So widespread did the talk become that one responsible citizen telephoned General Marshall and told him about it.
For Marshall, it was the latest headache in a long series. Security was always his most difficult problem in dealing with intelligence from cryptanalysis—MAGIC, or ULTRA, as it was sometimes called. Codebreaking successes are especially vulnerable to betrayal because of the ease with which a change of code can nullify them. The problem had existed since well before Pearl Harbor, when in his concern Marshall had ordered special zippered briefcases with padlocks, restricted the number of recipients, and generally tightened security on MAGIC. War aggravated the problem. The cryptanalytic agencies burgeoned, their output increased, the number of distributees rose.
Though the agencies insisted upon discretion as one of their prime recruiting criteria, the demand for personnel was so acute that some bad apples slipped into the barrel. Gossips, would-be big shots, and just plain thoughtless individuals bragged about how their work was winning the war. This reached a crescendo in the Yamamoto incident. Marshall had repeatedly sent oral requests through G-2 to F.B.I. Director J. Edgar Hoover to investigate the leaks, and particularly to nab some flap-jawed Army officer so that Marshall could make an example of him to discourage the loose talk. Hoover told Marshall that he was reluctant to probe another government agency for fear of being regarded as heading a Gestapo, but he did help. Unfortunately, the one strong case that they found was snagged by a legal technicality that would have prevented conviction.
The pre-Pearl Harbor policy of not indicating the source of communications intelligence disseminated to field commands was continued during the war. This extended to an ally, Russia. Related Marshall: “We have told them that we had good reason—not good reason—we had the best evidence that certain actions were going to be taken by the Germans against them, but we couldn’t tell them why, and there was quite a long debate as to whether we should not go into the whole thing, but that was felt most dangerous from two points of view. One was, we were spreading the thing out, and we didn’t know who all would become involved in it; and more particularly, they would probably get infuriated because they hadn’t had it from the start.”
This extreme caution cloaked MAGIC as far as it could go—to its very effects themselves. The third of four alternating red and black paragraphs printed on the cover of the Top Secret MAGIC summaries for European, Far Eastern, and diplomatic traffic stated: “No action is to be taken on information herein reported, regardless of temporary advantage, if such action might have the effect of revealing the existence of the source to the enemy.” This, of course, was a dilemma of the Yamamoto mission. So precious was MAGIC that the Allied command on occasion let convoys sail into the jaws of U-boat wolf packs rather than chance the Germans’ surmising that the Allies had a way of avoiding them. In the Pacific, American submarines were allowed to depredate Japanese merchant vessels on an ULTRA basis so uninterruptedly only because other intercepts showed that the Japanese thought that the vessel movements were reported to the Allies by coastwatchers; had they suspected cryptanalysis, the submarines would have had to hold off somewhat, for fear of losing long-term advantages.
In general, American security problems proceeded from MAGIC’s embarrassment of riches and its existence within a democracy. The first of these produced one of the three great security crises that plagued MAGIC during the war—the buzzing about the dramatically successful Yamamoto shooting. Democracy engendered the other two crises—one at the time of Midway, the other during a presidential campaign.
On the morning of Sunday, June 7, 1942, while Yorktown was still afloat and the Battle of Midway still, in a sense, in progress, the Chicago Tribune appeared on the streets with a column-long front-page story, headlined “Navy Had Word of Jap Plan to Strike At Sea.” Datelined “Washington, D.C., June 7,” it began:
The strength of the Japanese forces with which the American navy is battling somewhere west of Midway Island in what is believed to be the greatest naval battle of the war, was well known in American naval circles several days before the battle began, reliable sources in the naval intelligence disclosed here tonight.
The navy learned of the gathering of the powerful Japanese units soon after they put forth from their bases, it was said. Altho their purpose was not specifically known, the information in the hands of the navy department was so definite that a feint at some American base, to be accompanied by a serious effort to invade and occupy another base, was predicted. Guesses were even made that Dutch Harbor and Midway Island might be targets.
The story went on to describe the split-up of the Japanese armada into three forces and to give, in the greatest detail, the composition of these forces. It named the four carriers of the striking force and even went so far as to list—correctly—the four light cruisers that supported the occupation force. Near the bottom of the page, it asserted: “When it [the Japanese fleet] moved all American outposts were warned. American naval dispositions were made in preparation for the various possible attacks the Japs were believed to be planning.” The dispatch, which carried no byline, had been written by Stanley Johnston, a Tribune war correspondent who later authored Queen of the Flattops. Despite its dateline, he had written it in the Pacific.
At no point did the story refer in any way, even obliquely, to Japanese codes or to American communications intelligence. But the Navy feared that the Japanese would realize that its details could have come only from a reading of their coded messages. In August, the Justice Department appointed former Attorney General William L. Mitchell to direct a Chicago grand jury in determining whether the disclosure of confidential information violated the Espionage Act of 1917. The Tribune complained that it was being persecuted because the Secretary of the Navy, Frank Knox, published the rival Chicago Daily News. After a five-day closed inquiry, during which Johnston and the Tribune’s managing editor testified, the grand jury returned no true bill. None of The New York Times accounts o
f the investigation mentioned codes or suggested any reason for the nonindictment beyond Mitchell’s statement that “no violation of the law was disclosed.” However, it was widely recognized that the grand jury declined to indict because a trial would have called attention to something that, the authorities hoped, the Japanese might have missed. Their hope was fulfilled. The Japanese never saw it and never tumbled to the solution. Their switch to JN25d in August appears to have been unrelated.
After everything had been sewn up, a public indiscretion threatened to rip it open again. Representative Elmer J. Holland of Pennsylvania made a speech about the episode on the floor of Congress on August 31 which was carried far and wide by news stories. He was castigating the Tribune’s “unthinking and wicked misuse of freedom of the press.” “American boys will die, Mr. Speaker, because of the help furnished our enemies” by the Tribune, he declaimed. But in stating what this help was, he disclosed what the Tribune had not and trumpeted loud and clear what everyone was trying to hush up: “that somehow our Navy had secured and broken the secret code of the Japanese Navy.”
Fortunately, the Japanese missed that one too.
Potentially the most explosive situation stewed in the cauldron of national politics in the late summer of 1944. Republicans were preparing to run Thomas E. Dewey for President. High among their issues was the charge that inexcusable administration laxity had permitted the Japanese attack at Pearl Harbor to succeed so cruelly; there were even hints that President Roosevelt had deliberately invited the attack to get the country into “his” war over strong isolationist sentiment. Buttressing the charge was the knowledge, circulating secretly among many high officials, that the United States had cracked Japanese codes before Pearl Harbor. From this, many Republicans concluded that the decrypted messages had warned Roosevelt of Pearl Harbor and that he, with criminal negligence, had done nothing about it. This was false, but evidence to the contrary was not available and many men believed it.
As the campaign warmed up, bits and hints about MAGIC began to appear in political speeches. Representative Forest A. Harness of Indiana, for example, told the House on September 11 that “the Government had learned very confidentially that instructions were sent out from the Japanese Government to all Japanese emissaries in this hemisphere to destroy the codes.” The chief of Army intelligence, Brigadier General Clayton L. Bissell, reported these incidents to Marshall, who saw the danger of further revelations in the heat of contention for the greatest office of all. Bissell suggested that Marshall go to the President for help in squelching the talk. Marshall didn’t think that would do, and slept on it. Next morning he dictated a three-page, single-spaced letter to the Republican candidate pointing out the extreme danger of disclosing the MAGIC information. Because he felt that the success of his appeal depended on Dewey’s conviction that it was nonpolitical, he did not discuss the matter with either the President or the Secretary of War, and he began his letter, “I am writing you without the knowledge of any other person except Admiral King (who concurs).”
An Army security officer, tall, slim Colonel Carter W. Clarke, flew out West in a B-25 bomber to deliver the letter to Dewey, who had just given his first campaign speech devoted entirely to an attack upon the national administration. Clarke gave the sealed letter to Dewey on the afternoon of September 26 in a hotel in Tulsa, Oklahoma. Under “Top Secret” and “For Mr. Dewey’s eyes only,” its second paragraph stated: “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 this letter or not reading any further and returning the letter to the bearer.”
From a paragraph lower down, the word “cryptograph” leaped to Dewey’s vision. At once he guessed the subject of the letter, and since he had already learned the basic codebreaking secret from a number of individuals, and felt in any case that as a presidential candidate he was “not in a position to make blind commitments,” he stopped reading and returned the letter to Clarke.
When Clarke got back to Washington, Marshall discussed Dewey’s rejection with him and Bissell. They decided that the matter was so important that they had to try again, so after redrafting the first part of the letter, he sent Clarke—in civilian clothes this time—to Albany. Dewey, who was then governor of New York State, received him in the Executive Mansion on September 28, but declined to discuss the subject or read the letter except in the presence of one of his closest advisors, Elliott V. Bell, State Superintendent of Banks. He wanted to have corroboration of the occurrence in case something happened to Marshall, and for the same reason insisted upon keeping the letter, though Marshall had asked to have it returned. Clarke telephoned Marshall, who agreed to these conditions, and Dewey then came on the wire and promised to keep the letter locked up in his most secret file. He then read the most revealing single document in the annals of cryptology:
TOP SECRET
For Mr. Dewey’s eyes only.
27 September 1944.
MY DEAR GOVERNOR: Colonel Clarke, my messenger to you of yesterday, September 26th, has reported the result of his delivery of my letter dated September 25th. 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 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 knowledge 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 September 25th 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.
I should have much 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, with which Admiral King concurs, to be delivered by hand to you by Colonel Clarke, who, incidentally, has charge of the most secret documents of the War and Navy Departments.
In brief, the military dilemma 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 the information—but which unfortunately made no reference whatever to intentions toward Hawaii until the last message before December 7th, which did not reach our hands until the following day, December 8th.*
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 a
s well as Japanese, but our main basis of information regarding Hitler’s intentions in Europe is obtained from Baron Oshima’s messages 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 set-up 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 few ships were in the right place at the right time. Further, we were able to concentrate our limited forces to meet their naval advance on Midway when otherwise we almost certainly would have been some 3,000 miles out of place. 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 result from the fact that we know the sailing dates and routes of their convoys and can notify our submarines to lie in wait at the proper points.
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 of Japanese convoys, two of which were caught, as anticipated, in his destructive attacks.
