THE CODEBREAKERS

by DAVID KAHN

  But this was child’s play in comparison with the greatest radio deception of them all.

  The Germans called it a “Funkspiel,” and they could not have named it better. “Funk” means “radio,” while “Spiel” means “play” or “performance,” with secondary meanings of “game,” “sport,” and “match.” Even all these together do not fully express the connotation of the German. As one writer put it, “The word implies a mysterious carillon that rings out in the ether, sounding a Lorelei tune to mislead or entrap men who listen to it.”

  Director of the funkspiel that achieved more spectacular results than any other in World War II was Major Herman J. Giskes, 46, a Rhinelander who had spent most of his adult life in the German Army. Giskes was chief of the Netherlands branch of Section IIIF (counterespionage) of the Abwehr, but though the Abwehr had its own efficient mobile radio-intelligence units, Giskes came to use the radio-intelligence section of the Ordnungspolizei, an occupation police force, for this funkspiel.

  The Germans began tugging on the rope of the great carillon when they recruited a bloated, lame, perspiring Dutchman named George Ridderhof as a V-man. The V-men, posing as patriots, wormed into the Dutch underground and fed information to the Nazis. For a few months, Ridderhof, who was called F2078 by Giskes, registered little progress in his reports as he sought to gain the confidence of a cluster of Dutch agents working in The Hague.

  Meanwhile, the Abwehr radio-intelligence units had been intercepting and solving messages sent five times a week from an underground transmitter with call letters UBX. Gradually the direction-finders closed in, and suddenly, at 8 o’clock one morning, UBX was raided. Captured were the operator, his assistant, their ciphering material, the transmitter, and espionage material.

  This was Section IIIF’s first major success in Holland, and Giskes immediately began bending his thoughts to see whether UBX could be “played back” in a funkspiel. The advantages of a funkspiel are great. With the Germans operating a radio set that the Allies believed to be still in the hands of the underground, the Abwehr would be able to learn a great deal about enemy intentions from instructions sent out by London. It could exploit this information to frustrate Allied military excursions and to break up other Resistance groups. It could lace Allied intelligence with false information in the expectation that when plans based on this data miscarried Allied commanders would lose confidence in their intelligence. A funkspiel works in the ether precisely as a double-agent does in person. Because of its value, the Abwehr subordinated all other considerations to the possibility of reversing a Resistance station. The underground, on its part, was well aware of the danger of a funkspiel, and, to discourage the Germans, would booby-trap doors and radios and leave half-emptied bottles of poisoned brandy standing about.

  But UBX was not reversed. Some details necessary to make the playback sound authentic were missing, and the operator refused to divulge them under interrogation. Two other afus—as the Germans sometimes dubbed the agent radios, from their own highly compact but powerful clandestine transmitter—were captured, but attempts at reversing them also failed. These failures whetted Giskes’ appetite for a success.

  The possibility of one began glimmering in January, 1942. Ridderhof reported that the network that he had penetrated was about to receive equipment from Britain via a parachute drop that had been arranged by radio. “Go to the North Pole with your stories,” Giskes wrote angrily on the report. “There is no radio communication between Holland and England.” A few days later, however, the FuB, or intercept station, of the Ordnungspolizei heard a new radio link between station RLS in south Holland and PTX in England, north of London—a location that communicated with many of Europe’s underground radio stations. Ridderhof confirmed that his network was operating RLS, and his Abwehr contact man, in reporting this to Giskes, referred slyly to “Operation North Pole.” Giskes laughed, and Funkspiel NORDPOL got its name.*

  Close surveillance of RLS began at once. The FuB soon established its transmission routine, and direction-finding pinpointed the afu in an apartment house on Fahrenheitstraat, The Hague. Ridderhof dribbled information into the net, items both false and true, one of which, for example, confirmed that the cruiser Prinz Eugen was undergoing repair at Scheidam. Within a month, Section IIIF had gained enough knowledge of RLS to attempt a funkspiel. A raid was set for the next regular transmission period, with a virtually simultaneous roundup of the other agents, as much to keep them from disclosing the funkspiel as to quash the network.

  At 6 p.m. Friday, March 6, 1942, four disguised police cars blocked off Fahrenheitstraat. In the back seat of one, a man in plain clothes heard the key-clicks of a nearby transmitter as he sought the exact frequency. RLS was trying to raise London. Giskes planned to burst in before the radio operator made contact, to prevent his warning London. But the operator, tipped off by the owner of the apartment house that several cars filled with men were outside, broke off his transmission, gathered his three enciphered messages, and fled. He was apprehended a few yards away, and the police, breaking into the flat, discovered a small trunk, with the radio set and various papers in it, resting across two lines of washing in the rear garden, where the wife of the apartment house owner had dropped it.

  The cat-and-mouse game now began. The radioman, Hubertus M. G. Lauwers, had been prepared for just such a situation in the spy school he had attended while training in England as an underground agent. The Nazis, he had been told, would try, first through persuasion and then through torture, to win the cooperation of the radioman on the key so that no change of fist would become apparent to England. And since it was desirable for an agent to avoid torture, to prevent his spilling really important secrets, such as names of other members of the ring, the agent was directed to pretend to cooperate—warning England, however, that he had been captured and his radio compromised. He was to sound a silent alarm by omitting his security check from his compromised transmissions.

  The security check was an authenticator that the agent was to include in every one of his messages to prove their validity. It might consist of a number group, inserted at a prearranged point in the ciphertext, that had been obtained by adding together the date and a special number belonging to that agent alone. It might consist of the insertion of an x after every tenth letter of plaintext. It could take many forms. When a message came in without this check, or with what appeared to be a wrong security check (for the Germans could be expected to be as familiar with the technique as the Allies), a tocsin was to ring in London.

  Then the Allies would be able to funkspiel a funkspiel. While the Germans thought that they were tricking London, feeding it false information and milking it of true, London would have turned the tables on them and engorged the Germans on false data while deducing, by contradiction, the Germans’ real plans from the phony ones they sent London. And the Abwehr’s respect for funkspiel information as being especially accurate and valuable promised the Allies commensurate rewards for contaminating it. This outfoxing of the foxes, this reversing of a reversed radio and double-crossing a double-crosser—all these spymasters’ dreams of glory entered the realm of possibility with the recognition of the missing security check.

  Thus, so long as the true check was kept secret, Lauwers had little to fear, and even much to gain, from disclosing his method of operation. And, as he had been told in security school, the Nazi soft-sell began first, starting even before he had been taken from the Fahrenheitstraat. The head of the FuB unit, Lieutenant Heinrichs, stated that he could cryptanalyze the three messages found on Lauwers. However, Lauwers recalled, “He wanted to give me an opportunity of saving my skin by handing over the particulars of my code voluntarily, and he added that I could save him a lot of trouble by doing this. To me it seemed reasonable to meet this proposal, and I promised that I would fall in with his wish if he were to succeed in deciphering one of the three messages which had been found on me. To my surprise he agreed at once. He sat down at a table, seemingly immersed in
his ‘game of patience,’ and after about twenty minutes declared triumphantly, ‘I see—the cruiser Prinz Eugen is lying at Schiedam—eh?’ ” This was the message that Ridderhof had planted and that Heinrichs had used as a crib to crack the system.

  Lauwers, astounded at this demonstration of omniscience, kept his word to hand over the details of the cipher, which consisted of a double transposition with a group of nulls at the head and tail. He kept silent about his security check, however, until Giskes shocked him at the end of one interrogation by asking, “And what kind of mistake do you have to make?” For Lauwers’ security check consisted precisely in making a deliberate error in the sixteenth letter of the plaintext. The error had to be one that could not occur by the accidental addition or omission of a single dot or dash in the letter’s International Morse equivalent. Thus, an s (···) was not to be transformed to an i (· ·) or an h ( ····), but to, say, a t (−).

  As it happened, however, the sixteenth letter in two of the three captured messages was the o of stop. Lauwers had accordingly changed one o (−−−) to an i (··) and the other into an e (·). This fortunate coincidence enabled him to produce a false security check that agreed with what Giskes appeared to know. He told the Germans that his security check consisted of changing the word stop once in every message into step or stip. The Germans accepted this,* and Lauwers agreed to work the RLS transmitter for them, contriving to do the enciphering himself to perpetuate the false security check. He was confident that the Dutch section of Special Operations Executive, the British organization that managed underground activities in Europe, would spot the warning and take the proper measures.

  The first regular transmission period after the capture on March 6 came at 2 p.m. on March 12, and Lauwers sent the messages that he had not sent the night of the raid, which, of course, had the correct security check but also the information he was going to send anyway. In subsequent messages, RLS, directed by Giskes, asked that the drop point for an already arranged parachute drop be shifted from near Zoutkamp, which RLS now said was too isolated, to a moor near Steenwijk. On the 25th, S.O.E. acquiesced and, two days later, broadcast the signal for the drop itself. This was the crucial test. S.O.E.’s own security check and encipherment details seemed to be all right, but perhaps S.O.E. was itself planning a trap. Would the plane deliver bombs instead of supplies, blowing up not only the Abwehr’s hopes for a funkspiel but also part of the Abwehr itself? Lauwers, who expected that S.O.E. would detect his false security check, hoped so. Giskes, though unaware of Lauwers’ silent alarm, could nevertheless not be absolutely confident of success.

  On the 27th, Giskes and the German team huddled in the juniper bushes on the moor, and soon after midnight they heard the drone of aircraft engines. The plane headed for the triangle of red and white lights that the Germans shone upwards, and suddenly in its wake five large black shadows blossomed and rushed earthward. From the parachutes swung heavy black containers, which hit the ground with a dull thud. The plane blinked its navigation lights and disappeared westward into the mist. The Germans, scarcely able to believe their luck, pressed one another’s hands in dumb joy. The first of many echoes had come back from the pealing of the great carillon.

  And the security check? Why had its alarm not gone off? Because of stupidity and incompetence within S.O.E., with a single factual condition as an alibi. This condition was the weakness of the agents’ radios and the agents’ poor abilities as operators. Consequently, messages seldom arrived with perfect accuracy. In some cases, the decipherers in the Dutch section of S.O.E. could not tell whether an error was a deliberate one to conform to the security check or just an ordinary garble. From 5 to 15 per cent of the messages were so unclear that the decipherers were happy if they could just read the text—with these, they were not concerned with security checks. But even granted this, the negligence of S.O.E. bordered on the criminal. The vast majority of messages in which there was no question but that the crucial security check was missing were regarded as bona fide by the organization. Some messages were even marked “Identity check [same as security check] omitted”; S.O.E. did not reject them. Thus, by disregarding the precautions which it had itself instituted, S.O.E. fell headlong into a funkspiel.

  NORDPOL’s first success was followed by others. A succession of air drops took place, each one increasing Giskes’ confidence in the success of his funk-spiel. Then, at the beginning of May, 1942, a series of Resistance mishaps, skillfully exploited by the Germans, delivered into their hands the radio links, and hence the control, of all underground networks in Holland. Two two-man rings, called TURNIP and HECK by the S.O.E., had been parachuted into Holland; their radios had been damaged in the drop, and they contacted group LETTUCE to report their problems to London. Meanwhile, the NORDPOL group, which was known as EBENEZER to S.O.E., was directed to contact LETTUCE to help an agent of still another ring, POTATO. The Nazis rounded up these agents before they could warn London, and on May 5, Giskes began operating the LETTUCE transmitter in a second funkspiel. In this one, a captured agent, Hendrik Jordaan, betrayed his security check.

  Eventually the Giskes-Schreieder combine was running fourteen funk-spiels with S.O.E. Hitler himself was regularly reading reports on it that gave the texts of many of the messages; these were submitted by Himmler. The all-important security check continued to be omitted from many of the transmissions—Lauwers alone transmitted checkless messages for seven months. S.O.E. actually bestirred itself a few times to wonder whether the Dutch operations had been penetrated and should therefore be terminated. Each time it decided to continue them because it felt that the security checks were “inconclusive as a test.” The full scale of the Dutch section’s bungling is displayed in the fact that the fourteen transmitters were operated by only six FuB radiomen, who were so overworked that Giskes sought to eliminate some sets by reporting that they had been knocked out by German action. S.O.E. had obviously either never recorded its agents’ fists before sending them out or never bothered to check their supposed transmissions against any transcriptions that they might have made. On the other hand, many of the messages did have the correct security check. Credit for much of the authenticity of many of these messages must go to Schreieder’s cryptologic specialist, Ernst Georg May, a corpulent, crew-cut Prussian in his late thirties, who thoroughly studied the Resistance cipher systems and the recurrent “mistakes” therein.

  Keeping NORDPOL going involved a good deal more than thinking up fairy tales to put on the air. What was to be done about orders received from S.O.E.? How could the Abwehr maintain S.O.E.’s confidence that its underground networks were all operating healthily? Giskes resorted to a variety of elaborate charades, excuses, and, in a few cases, actual aids to the Allies. Most of the latter involved helping downed airmen escape to Spain. When these reached England, they extolled the help given them by GOLF, one of the Dutch Resistance groups. They never realized that GOLF’s extraordinary success was due to its direction by a German officer, and S.O.E., confronted by proof positive of GOLF’s efficacy in the form of living Allied airmen, suspected nothing. In another case, when S.O.E. ordered EBENEZER to blow up an Occupation antenna complex, Giskes reported that a minefield had thwarted their attempt. S.O.E. accepted the excuse, saying that the defense was unforeseeable. When one new agent parachuted into Holland and found himself in the Abwehr’s arms, he told his captors that unless he sent the code message THE EXPRESS LEFT ON TIME by 11 a.m. S.O.E. would know that he had been nabbed. Giskes, thinking fast, signaled London through another funkspiel that the agent had landed heavily and was unconscious. Four days later, S.O.E. was told that he had died without gaining consciousness. Giskes even went so far as to sabotage a barge in Rotterdam harbor before an audience of thousands of cheering Dutchmen—and then, after reporting it as a Resistance coup, planted stories in the German-controlled newspapers in the hope that they would get to England and corroborate his reports.

  Lauwers, on the other hand, was going frantic. After thin
king at first that London had reversed the Abwehr radio, he finally realized that there had been a serious slip, and he began to look for other means of alerting S.O.E. He first sent the word caught by altering the Morse equivalents of the radioman’s standard Q-code signal QRU (−−·−·−· ··−), meaning “I have nothing further for you,” to cau, (−·−· ·−· ·−), and the Morse of his call-sign, which he himself could select and which followed QRU, to ght. Though he slipped this past the German operators, developments gave no indication that London had recognized the cue. He then tried to spell out caught by altering a likely five-letter ciphertext group and adding on the single dash for a t; to increase the chance of a suitable group appearing, he used C, G, and H almost exclusively as his nulls. He then transmitted CAUGHT as if it were an error, repeating this error several times in pretended self-irritation so that it would be picked up several times in England, and finally sending the text correctly. No response.

  With agents falling like flies into the hands of the Nazis, Lauwers and his cellmate, Jordaan, the operator who had betrayed his check, determined to try once more with a scheme that was more difficult but that might show up more clearly in England. They would make a warning message out of the nulls at the head and tail of two messages. The Germans prohibited the use of vowels in the nulls at the head and tail of their plaintexts, so the Dutchmen had to use consonants in place of the vowels of their clandestine message, follow these consonants through the two transposition blocks, mentally reconvert them to vowels in the cryptogram, and then transmit these vowels as if they were errors for the consonants. The two practiced this difficult process in their cell and managed to pass the first part of their message. But then Giskes changed procedure: a German operator read the cryptogram off letter by letter, perhaps to prevent just such tricks, and the second half was never sent. It probably didn’t matter anyway: the first part went unheeded.