by DAVID KAHN
It exploded on February 22, 1917. Unable to wait any longer, the British gave the cork a push. Hall, with Foreign Office approval if not under its orders, showed the Zimmermann telegram to Edward Bell, a secretary of the American embassy who maintained liaison with the various intelligence offices of the British government. He read an astounding tale of German intrigue against his country:
We intend to begin on the first of February unrestricted submarine warfare. We shall endeavor in spite of this to keep the United States of America neutral. In the event of this not succeeding, we make Mexico a proposal of alliance on the following basis:
Make war together, make peace together, generous financial support, and an understanding on our part that Mexico is to reconquer the lost territory in Texas, New Mexico and Arizona. The settlement in detail is left to you.
You will inform the President [of Mexico] of the above most secretly, as soon as the outbreak of war with the United States of America is certain and add the suggestion that he should, on his own initiative, invite Japan to immediate adherence and at the same time mediate between Japan and ourselves.
Please call the President’s attention to the fact that the ruthless employment of our submarines now offers the prospect of compelling England in a few months to make peace.
Zimmermann.
Bell did not believe it. The notion that anyone in his right mind would consider giving away a chunk of the continental United States was simply too preposterous. But Hall convinced him of its authenticity, and the two went over to Grosvenor Square. When Page saw the message, he realized at once that the entry into war on England’s side, which he had so single-mindedly pursued and the President had so obstinately opposed, was at last delivered into his hands. Hall, Bell, Page, and Irwin Laughlin, first secretary of the embassy, spent the day trying to decide how best to instill confidence in the telegram’s genuineness, to minimize incredulity, and to maximize its impact. They decided that the British government should officially present the telegram to Page, and in his room at the Foreign Office the next day Arthur Balfour, now secretary of state for foreign affairs, formally communicated it to Page in a moment that Balfour later confessed was “as dramatic a moment as I remember in all my life.”
Page worked all night to draft a covering message explaining how the telegram was obtained. At 2 a.m. February 24 he cabled, “In about three hours I shall send a telegram of great importance to the President and Secretary of State,” but it was not until 1 p.m. that the Zimmermann telegram, with his explanation, was transmitted. He gave the President the collection of half-truths that Hall had given him—for Hall naturally withheld the deep secret of British cryptanalytic ability, particularly since it might start the Americans wondering whether Britain was reading their code messages as well:
Early in the war the British government obtained possession of a copy of the German cipher code used in the above message and have made it their business to obtain copies of Bernstorff’s cipher telegrams to Mexico, among others, which are sent back to London and deciphered here. This accounts for their being able to decipher this telegram from the German government to their representative in Mexico, and also for the delay from January 19th until now in their receiving the information. This system has hitherto been a jealously guarded secret and is only divulged to you now by the British government in view of the extraordinary circumstances and their friendly feeling toward the United States. They earnestly request that you will keep the source of your information and the British government’s method of obtaining it profoundly secret, but they put no prohibition on the publication of Zimmermann’s telegram itself.
Page’s pilot telegram rattled the Morse sounders at the State Department at 9 a.m. Saturday, February 24, but the “telegram of great importance” did not arrive until 8:30 that evening. Frank L. Polk, counselor of the department and acting secretary in the absence of Secretary of State Robert L. Lansing, telephoned to ask the President to expect him and carried the four typewritten yellow sheets across the street to the White House. Wilson, Polk reported, showed “much indignation” on reading it, and wanted to make it public at once. But he agreed to Polk’s suggestion to await Lansing’s return from a long weekend.
On Tuesday, February 27, Lansing came back from White Sulphur Springs. Polk told him about the Zimmermann telegram and showed him an exceptionally long cable of 1,000 codegroups that he had found in the State Department files. It had come for Bernstorff in an American cablegram of January 17 from Berlin and was, Polk felt, almost certainly the coded original. (It was, in fact, the double-decker, which included the Zimmermann telegram.) At 11 that morning, Lansing, armed with this, discussed the whole situation with the President, who exclaimed “Good Lord!” several times at the outrageous German abuse of the cable privileges he had extended them. He consented to Lansing’s plan to release the telegram through the press, which Lansing felt “would avoid any charge of using the document improperly and would attract more attention than issuing it openly.” Accordingly, at 6 p.m. the next day, E. M. Hood of the Associated Press was called to Lansing’s home, given the message and some background details, and pledged to secrecy on the greatest scoop of the war.
The story broke in eight-column streamers in the morning papers of March 1. “Profound sensation,” Lansing noted. The nation gasped. In Congress, the House orated patriotically and passed by 403 to 13 a bill to arm merchant ships. But the Senate, more deliberate, wondered whether the whole thing was not just a crude Allied plot. This reaction had been foreseen. Lansing had asked Page to “Please endeavor to obtain copy of German code from Mr. Balfour,” but the British had told him that the code was “never used straight, but with a great number of variations which are known to only one or two experts here. They can not be spared to go to America.” This was, of course, another half-truth—the 0075 message was probably superenciphered (the “variations”) but the 13040 one was not. Polk, meanwhile, exerted tremendous pressure on Newcomb Carlton, the president of Western Union, and finally managed to get a copy of Bernstorff’s telegram to Eckardt despite a federal law protecting the privacy of telegrams. Lansing appended this code-text to the wire he sent Page at 8 p.m. the day of the exposé:
Some members of Congress are attempting to discredit Zimmermann message charging that message was furnished to this government by one of the belligerents. This government has not the slightest doubt as to its authenticity but it would be of the greatest service if the British government would permit you or someone in the Embassy to personally decode the original message which we secured from the telegraph office in Washington, and then cable to Department German text. Assure Mr. Balfour that the Department hesitated to make this request but feels that this course will materially strengthen its position and make it possible for the Department to state that it had secured the Zimmermann note from our own people.
The message, No. 4494, was received the next day, and by 4 p.m. Page cabled back: “Bell took the cipher text of the German messages contained in your 4494 of yesterday to the Admiralty and there, himself, deciphered it from the German code which is in the Admiralty’s possession.” In fact Bell wrote only a dozen or so plaintext groups before letting de Grey do the rest in his neat handwriting. Page then sent the German text as decoded by Bell and de Grey. But Lansing and the President had already sent up to the Senate a statement that the government possessed evidence establishing the telegram as genuine, and that no further information could be disclosed.
Everyone already had his own pet theory of how the United States had gotten it. Most popular was the spy story. Most farfetched was that four American soldiers had found it on a German agent trying to cross into Mexico. Most plausible was that the telegram had been found among Bernstorff’s effects when his baggage was searched at Halifax after his dismissal. Most amusing were the attacks by the British press on the inefficiency of their secret service and its inferiority to the American. (At least one of these was instigated by Hall himself to throw the theorizer
s off the scent.)
Wilhelmstrasse, too, wondered where the leak had occurred. Though the message as published in the papers did not carry either Bernstorff’s heading or his serial number, it did bear the significant date January 19. “Please cable in same cipher,” the Foreign Office purred at a quivering Eckardt, who had already tried to blame Bernstorff for the betrayal, “who deciphered cable dispatches 1 [the Zimmermann telegram] and 11 [ordering Eckardt to negotiate at once for the proposed alliance], how the originals and decodes were kept, and, in particular, whether both dispatches were kept in the same place.” Six days later, it picked up the clue that Hall had carefully planted: “Various indications suggest that the treachery was committed in Mexico. The greatest caution is indicated. Burn all compromising material.”
Eckardt mustered impressive details to exculpate himself: “Both dispatches were deciphered, in accordance with my special instructions, by [Dr. Arthur von] Magnus [the legation’s corpulent secretary]. Both, as is the case with everything of a politically secret nature, were kept from the knowledge of the chancery officials…. The originals in both cases were burned by Magnus and the ashes scattered. Both dispatches were kept in an absolutely secure steel safe, procured especially for the purpose and installed in the chancery building, in Magnus’ bedroom, up to the time when they were burned.” Three days later, he sent in his reserves: “Greater caution than is always exercised here would be impossible. The text of telegrams which have arrived is read to me at night in my dwelling house by Magnus, in a low voice. My servant, who does not understand German, sleeps in an annex…. Here there can be no question of carbon copies or waste paper.” The shrieks of hilarity that this occasioned Hall, Page, and Room 40 were not heard in Berlin. Its last doubts swept away by the low voice, the steel safe, the scattered ashes, and the non-German-speaking servant, the Foreign Office capitulated. “After your telegram it is hardly conceivable that betrayal took place in Mexico. In face of it the indications which point in that direction lose their force. No blame rests on either you or Magnus.”
Nigel de Grey transcribes the Code 13040 version of the Zimmermann telegram into plaintext for the skeptical Americans
“Exploding in his Hands.” Cartoon by Rollin Kirby in The [New York] World just after the Zimmermann telegram was made public
Meanwhile, the problem of authenticity, which had so troubled the Anglo-American officials and stirred uneasy questioning in the Senate and the press, had been eliminated by Zimmermann himself. Completely unexpectedly, he confessed: “I cannot deny it. It is true.” Knowledge of the plot had been blandly disavowed by the Mexicans, the Japanese, and Eckardt, and to this day no one knows why Zimmermann admitted it. His acknowledgment buried the last doubts that the story might have been a hoax.
Suddenly, Americans in the middle of the continent who could not get excited about the distant poppings of a European war jerked awake in the realization that the war was at their border. Texans blinked in astonishment: the Germans meant to give away their state! The Midwest, unmoved because untouched by the submarine issue, imagined a German-officered army crossing the Rio Grande and swung over to the side of the Allies. The Far West blew up like a land mine at the mention of Japan. Within a month, public opinion crystallized. Wilson, who three months before had said that it would be a “crime against civilization” to lead the nation into war, decided that “the right is more precious than peace” and went up to Capitol Hill on April 2 to ask Congress to help make the world safe for democracy. He cited the Zimmermann telegram in his address:
“That it [the German government] means to stir up enemies against us at our very doors, the intercepted note to the German minister at Mexico City is eloquent evidence. We are accepting this challenge of hostile purpose…. I advise that the Congress declare the recent course of the Imperial German Government to be in fact nothing less than war against the government and people of the United States, that it formally accept the status of belligerent which has thus been thrust upon it.”
The Congress did. Soon the Yanks were coming. The fresh strength of the young nation poured into the trenches of the Western Front to rescue the exhausted Allies. And so it came about that Room 40’s solution of an enemy message helped propel the United States into the First World War, enabling the Allies to win, and into world leadership, with all that that has entailed. No other single cryptanalysis has had such enormous consequences. Never before or since has so much turned upon the solution of a secret message. For those few moments in time, the codebreakers held history in the palm of their hand.
10
A WAR OF INTERCEPTS: I
RADIO, envisioned by its inventor as a great humanitarian contribution, was seized upon by the generals soon after its birth in 1895 and impressed as an instrument of war. For it immeasurably magnified the chief military advantage of telegraphy: instantaneous and continuous control of an entire army by a single commander. By eliminating the need for physical linkage by wire, radio speeded communication between headquarters, joined through the ether units that could not connect by wire because of distance, terrain, hostile forces, or rapid movement, opened communications with naval and air forces, and eased the economic burden of producing immense quantities of wire.
But few blessings are unmixed. Just as the telegraph had made military communications much more effective but had also increased the possibility of interception over that of hand-carried dispatches, so radio’s vast amplification of military communications was accompanied by an enormously greater probability of interception. The public, omnidirectional nature of radio transmissions, which makes wireless communication so easy to establish, makes it equally easy to intercept. It was no longer necessary to gain physical access to a telegraph line behind the enemy’s front to eavesdrop upon his communications. A commander had only to sit in his headquarters and tune his radio to the enemy’s wavelength. Radio thereupon introduced two revolutionary factors in the interception of communications: volume and continuity.
Communications are intercepted, of course, so that they may be submitted to cryptanalysis. Now cryptanalysis has a potential that cryptography does not. Cryptanalysis can alter the status quo. Cryptography can at best conserve it. Cryptanalysis can bring countries into war, engender naval battles and win them, compel besieged cities to yield, condemn queens to death and prove innocent the unjustly accused. Cryptanalysis hammers upon the real world. Cryptography does not.
Consequently, the telegraph, which affected only cryptography, had had a wholly internal influence upon cryptology. That a hierarchy of special systems had arisen to displace the nomenclator interested only cryptologists; it did not matter to generals or statesmen. And although the telegraph greatly increased the volume of communications, wiretapping could produce intercepts only at rare and irregular intervals. Cryptanalysis could exercise only transient and haphazard effects. Its potential remained largely unfulfilled. Kerckhoffs accurately regarded it as an auxiliary to cryptography, a means to the end of perfecting military codes and ciphers. Cryptanalysis during the telegraph years was interesting but inconsequential, intriguing but academic—an ideal topic to pass a Victorian tea-time, perhaps, but not much more.
The radio, however, turned over to the commander a copy of every enemy cryptogram it conveyed. It furnished a constant stream of intercepts. And with these, cryptanalysis could bear continually upon operations, could be depended upon for information, could affect events decisively. The generals and the statesmen took notice. This was no longer a polite trifling discussion; this had become a weapon, a pursuit entailing all the savagery of warfare and life against death. Radio made cryptanalysis an end in itself, elevating it to an importance coordinate with that of cryptography, if not superior to it. Radio’s impact upon cryptology reverberated in the outside world.
Wire and wireless thus complemented one another. The telegraph created modern cryptography; the radio, modern cryptanalysis. The one developed cryptology internally, the other externally. The telegraph had
given cryptology shape and content; now the radio carried it out into the arena of life. One gave it form; the other, meaning. The radio completed the work that the telegraph had begun. And so it was that radio, first widely used in the Great War of 1914 to 1918, brought cryptology to maturity.
On the Western Front, only France was ready. Her prewar activities, more extensive and better conceived than those of any other nation, had prepared her. Posts that had intercepted German radiograms in peace simply continued to do so in war. The cipher system approved by the Commission on Military Cryptography went into effect. The cryptologic section set up by Cartier at the War Ministry was quickly fleshed out with mobilized personnel. His assistant, Major Marcel Givierge, arrived alone at general headquarters to set up a cryptologic section—and a week later had six assistants working round the clock. For the first few days, there was little to do, but when the invading Germans crossed the frontier early in August, passing beyond the wires of their telegraph network, their messages filled the air.
