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The Eureka-Rebecca compromises: another look at special operations security during World War II.

One month after World War II, Major General Sir Colin Gubbins, the Chief of the British Special Operations Executive (SOE), requested that the Washington Headquarters of the American Office of Strategic Services (OSS) search its captured German document collection for information regarding German wartime knowledge of SOE or OSS secret operations. Both the SOE and the Special Operations Branch of the OSS ran hundreds of clandestine operations during the war, parachuting agents far behind enemy lines. Yet, SOE's discovery in 1944 of the German security services' infiltration of SOE's Holland agent network, together with the beginning of acrimonious postwar debates about SOE's failure in Holland, necessitated Gubbins' investigation into German records. (1)

OSS Washington forwarded Gubbins' request to the OSS London office, then in the process of consolidating its operational files with the war now over. The London office produced four captured documents that dealt with Allied special operations, but none of the items proved pertinent to Gubbins' specific inquiries. One of these documents, however, would have interested any of the clandestine services during the war had it been forwarded to their air operations personnel. The document indicated that German army intelligence had issued a secret directive on the British Special Air Service (SAS). (2) Although the directive consisted only of a general, two-page narrative on SAS tactics, it indicated German familiarity with a special piece of electronic equipment carried by SAS, SOE, and OSS teams--a compact radar navigation homing beacon which those groups had considered a closely held secret. The Allies nicknamed this radar set Eureka, a Greek term meaning, "I have found it."

Recently declassified OSS records show the regular employment of Eureka radar beacons in clandestine drop zone (DZ) operations. (3) Allied special operations groups--the SAS, SOE, and the OSS--relied upon portable Eureka sets in all theaters because the ground-based, pre-positioned radar beacons enabled Allied aircraft, equipped with the Rebecca counterpart, to locate agent and supply DZs far behind enemy lines. Yet, deploying the highly classified beacons in enemy territory held substantial risk because these sets, if captured, could be activated to lure unsuspecting airborne agents and commando teams to certain capture. Although OSS documentation discloses the training, employment, and extreme secrecy surrounding Eureka-Rebecca system, these records also reveal that Allied special operations commands neglected to weigh the possible consequences whenever agents lost Eureka sets either accidentally during nighttime airdrops, or directly to the enemy. (4) Furthermore, the postwar inquiries into SOE's Holland disaster confirmed what may have been suspected--yet not circulated throughout the special operations community--that as early as 1942 the Germans had captured and activated Eureka beacons in order to manipulate Allied DZs. Due to these gaps in operational security, Allied commands continued to issue Eureka beacons throughout the war without modifications that would limit their vulnerability to further enemy exploitation.

More than sixty years later, historical assessments of enemy technical countermeasures to Allied special operations tend to concentrate on German Funkspiele or "radio games," that often deceived Allied special operations headquarters through the playback of captured agent radio transmitters. This paper builds upon that premise and suggests that, in certain cases, German manipulation of the Allies' Eureka-Rebecca system could not only in theory produce an effective countermeasure, but could also compromise an important layer of Allied security and provide Berlin the initial, technical capability to infiltrate Allied special operations. German manipulation of Eureka-Rebecca could theoretically simulate special operations DZs to establish a trap for the capture of Allied personnel, and to help provide a foundation for the subsequent radio games whose devastating impact ended so many clandestine operations. (5)

Early Compromises of the Eureka-Rebecca System

After the fall of France in 1940, London gradually introduced clandestine operations into the European Theater to destabilize the German occupation. Operations by air, however, had delivered only a few agents by 1942. This modest start reflected not only the beginnings of a new type of warfare, but also the constraints of successfully delivering agents by air during the limited full-moon period available each month. In 1941, following the Air Ministry's substantial success with defensive radar development and employment during the Battle of Britain, the British Telecommunications Research Establishment (TRE) developed a concept employing a small ground-based radar beacon that enhanced clandestine air navigation, particularly at night. TRE personnel nicknamed the ground portion Eureka, and the airborne counterpart Rebecca, and began developing test sets for some of the first British special operations. (6)

London fielded preliminary versions of an "Mk I" Eureka radar beacon in Holland and Czechoslovakia, where the devices first fell into German hands. In March 1942, the British Royal Air Force (RAF) dropped three SOE-trained Czech agents into German-occupied Czechoslovakia. This team, code-named Out Distance, carried one of these beacons. Out Distance's unique mission required the placement of the Eureka beside the Czech Skoda steel works, at that time producing weaponry for the German armed forces. The RAF planned to send bombers to home-in on the beacon, and destroy the factory. Like a number of the Czech teams dropped into Czechoslovakia in 1942, however, Out Distance found conditions there extremely hostile, and two of its three members quickly fell victim to the Gestapo (German Secret State Police). A Czech farmer subsequently found their Eureka beacon hidden on his farm and turned it over to the Gestapo. (7) Shortly after the neutralization of Out Distance, SS Lt. Gen. Reinhard Heydrich, the former Gestapo chief recently appointed acting Reichsprotektor of Czechoslovakia, wrote Adolf Hitler's aide, Martin Bormann. In his memo, Heydrich reviewed the recent capture of clandestine equipment in Czechoslovakia, and drew a link to reports he had read about similar "modern equipment" German intelligence recently discovered in Holland. (8)

In March 1942, the counterintelligence service of the German armed forces high command, the Abwehr, began Operation "North Pole," a long-term penetration and manipulation of SOE's Holland agent network. By 1944 the Abwehr in Holland, under the direction of Maj. H. J. Giskes, would capture more than fifty British agents, most of Dutch nationality, which London had sent back into the Netherlands for sabotage operations. In one of the longest and most disastrous radio games of the War, the Abwehr teamed with the German SS Security Service (SD), to force captured agents to radio false messages to SOE's Dutch section in London. They intended to deceive SOE into continuing additional DZ operations that would also fall under German control. Berlin could then neutralize or manipulate Allied clandestine operations in the country. (9) In May 1942, Giskes' team, with the assistance of Dutch police impersonating resistance agents, captured SOE's Beetroot team on their own DZ, along with the team's Eureka beacon. SOE had recently trained the two Dutch operatives of Beetroot on the Eureka system, in order that they could then instruct other agents in Holland on its use. German radio experts, when they first analyzed Beetroot's Eureka, concluded the set was some type of aircraft beacon device; but the Abwehr did not understand its true use until told by Beetroot's agents under interrogation. The German Abwehr essentially received a description of the Eureka's operation by experts specifically trained to teach Eureka use to Allied agents. (10)

The Eureka beacon presented a unique problem for Allied designers, because the secret system had to be employed behind enemy lines. While the range and frequencies of the Eureka system remained classified until the end of the war, the Allies considered the fact that their agents used such a device, secret through most of 1943. To avoid compromise of Eureka beacons, therefore, Britain's TRE engineered security features into the beacon design. Yet these protective measures failed in both Czechoslovakia and Holland. The Eureka's passive frequency design (the beacons activated only when prompted by friendly aircraft emitting Rebecca's interrogating frequency), intended to deny enemy electronic "direction-finding" operations against active beacons, could prove irrelevant. For instance, the Gestapo captured intact Out Distance's Eureka hidden away at a farm; and the Abwehr's radio game with SOE put Beetroot's DZ (and their Eureka) directly in German hands. In both cases, the assumed electronic countermeasure difficulties against a passive system like the Eureka never materialized. In addition, the lack of an agent's supplemental flashlight signal, typically required to assure approaching Allied aircraft that the beacon was in friendly hands, proved irrelevant in Holland. On his first attempt to use the Eureka in Holland, Giskes took the beacon to a known Allied DZ, and waited until late evening to activate the set. Giskes' team heard an approaching RAF aircraft, but never sighted the plane in the pitch-black sky and never attempted a supplemental flashlight signal; but Giskes did receive a drop of six Allied equipment containers intended for Dutch resistance. Giskes' first employment of his captured Eureka required no supplemental security whatsoever. (11)

Giskes continued to capture additional Eureka radar beacons until 1944, when London had deduced the German penetration of its Holland agent network. (12) During this period German counterintelligence managed as many as thirty false DZs in Holland to entrap parachuting agents. The Abwehr's correct employment of captured Eurekas at many of these DZs permitted the continued deception of SOE's Dutch section in London. Eureka manipulation became a ruse critical to the success of Berlin's main deception effort against Allied special operations--the subsequent playback of captured radio sets, the disastrous impact of which is widely acknowledged today. After London's postwar investigation into the Holland debacle, British intelligence could certainly conclude that the Eureka was compromised. But during the War, there appears to have been no recommendation to change the frequencies of new Eureka production models, and Eureka technology carried no warning about its potential compromise when in early 1943 design plans for the British Eureka-Rebecca system arrived in Washington for mass production by American industry. (13)

In early 1943, Britain's TRE briefed U.S. Army Signal Corps officers on the operation of the Eureka-Rebecca system. The Signal Corps saw immediate use for the Eureka beacon in U.S. airborne operations, and arranged priority shipment to the War Department of design plans and samples of the British Eureka beacon and the airborne interrogating component, Rebecca. (14) But the War Department had already tested the Eureka-Rebecca system. A few months earlier the Signal Corps had ordered one of its TRE-trained Signal Corps officers to fly from London to Gibraltar to brief the OSS, which planned to employ the Eureka beacon for the impending November 1942 Allied landings in Algeria, North Africa, codenamed Torch. In late October, as Capt. Gordon Browne of the OSS, sat at his communications post in Gibraltar, he received orders to attend a secret meeting at the British governor's Gibraltar residence. Upon his arrival, a Signal Corps officer laid out an Mk I Eureka beacon on the governor's living-room floor and instructed Browne on its use. Browne's mission was strategic: he was to courier the Eureka to Morocco and, shortly before the November 8 invasion, smuggle the secret device into Algeria and activate the beacon near airfields just outside of Oran. U.S. Army Air Forces (AAF) C-47 transport aircraft originating from England were then to home-in on the Eureka beacon, and drop American paratroopers to capture the airfields from Vichy French forces. (15)

One month after the Torch landings, Browne sent a copy of his after-action report to the OSS chief, Col. (later General) William A. Donovan. Browne recommended immediate adoption of the Eureka beacon for OSS clandestine DZ operations. In Washington, Donovan forwarded Browne's report to his communications branch. These officers also recommended OSS acquisition of the Eureka system, and warned that "Because of the extreme secrecy surrounding this apparatus," OSS procurement should be handled only at the highest channels. Eureka secrecy explains why OSS Washington had not previously learned of the device, but its inquires soon found that the Signal Corps was already examining British Eureka sets obtained through a highly classified procurement project. Donovan's staff subsequently recommended against duplication of effort, leaving the Signal Corps with sole responsibility for procurement. (16)

The Torch landings, however, introduced to the Americans the difficulties they too would experience attempting to ensure Eureka security. Browne's after-action report described the near-capture of his Eureka by Vichy French forces. An unfortunate risk, since bad weather over the Bay of Biscay had already dispersed the C-47 paratroop transports; most aircraft became lost, and none came close enough to trigger the Eureka beacon and establish a radar link to the Oran DZ. (17) Lost pilots diverted their C-47s to emergency landing fields across much of the North African coast. A few aircraft landed farther west in neutral Spanish Morocco, where Spanish authorities interned the planes and their crews. The crew of one of these C-47s failed to destroy the aircraft's instruments before internment--instruments that probably included an early version of Rebecca. Neither the Signal Corps nor presumably Britain's TRE learned of the possible compromise. (18) Nevertheless, German intelligence soon afterward captured a Rebecca set in Europe. Allied bombers based in England conducted numerous special operations and agent supply operations over Holland and, according to the Abwehr's Major Giskes, in early 1943 Luftwaffe (German airforce) technicians pulled a Rebecca set from a crashed British bomber. Moreover, by mid-1943 Allied ground crews received orders to outfit conventional bombers with the Rebecca radar set. While this addition increased operational efficiency--aircraft pulled from scheduled bombing missions to support agent supply operations would not require time-consuming Rebecca retrofitting--it also increased the odds of Rebecca compromise in emergency landings behind enemy lines. (19)

These early-war compromises continued. During the July 1943 Allied landings in Sicily, American airborne and British airborne and SAS units employed early forms of radar beacon technology. Whereas the British employed early models of their Eureka beacons, the Americans modified existing versions of the U.S. AAF's Mk III IFF ("identification, friend or foe") radar system because American-produced Eurekas were not yet available. Allied fighter and bomber units normally fitted the IFF system in the forward sections of their aircraft, so that airfields and ships could identify friendly aircraft. Since the IFF and Eureka beacon shared similar operating principles, American airborne units in Sicily used existing IFF sets as interim ground navigation beacons. But the security of this system was in doubt too. By the end of 1943, Allied intelligence reports from both the European and Pacific theaters indicated that German and Japanese forces had captured the Mk III IFF system. Worse, they were mimicking the system in order to deceive Allied forces. (20) These examples suggest that by the early stages of U.S. Eureka production the enemy had already developed an ability to manipulate not only the early British Eureka models captured in Czechoslovakia and Holland, but other types of emerging radar beacon technology as well. If so, even short-term security may have been impossible to maintain for classified radar systems meant for use inside, or over, enemy territory.

U.S. Eureka Beacon Development and Employment

In early 1943, London forwarded the design plans and samples of the British Eureka-Rebecca system to the U.S. War Department, which then ordered the Signal Corps to procure the same design manufactured with the latest U.S. technology. But the momentum for a U.S. Eureka-Rebecca system also came from another source. Secretary of War Henry Stimson was a proponent for the fastest possible design and fielding of new radar systems. Moreover, Stimson's cousin had recently established the new radiation laboratory, or "Rad Lab," at the Massachusetts Institute of Technology (MIT). The Rad Lab worked with the Signal Corps and its contractors to review the feasibility of emerging radar technology, and one of Rad Lab's projects dealt with the conversion of the British Eureka beacon to U.S. specifications. (21) Stimson's link with the Rad Lab provided support for a U.S. Eureka from the highest level, and on at least one occasion the Secretary of War personally promoted the Eureka beacon at a 1943 Thanksgiving dinner with the top OSS operations executive. (22)

U.S. and British Eurekas would share five frequencies for standardization. Transmitter and receiver frequencies of both models (including their Rebecca counterparts) began at 214 megacycles per second (Mc/sec), and increased at five Mc/sec increments to 234 Mc/sec. Although the early Mk I Eureka featured only one frequency, the newer Eureka and Rebecca sets could transmit or receive on any one of the five predetermined frequencies as long as the transmitting and receiving frequencies differed by at least a five Mc/sec increment. The total frequency mix provided twenty possible transmitting-receiving modes, thereby offering a modicum of security. (23) But most military radios of the time, including the clandestine "suitcase" radios carried by agents, would accept numerous removable "crystals," or frequencies, that offered many more frequency choices--the Eureka radar beacon did not. But in April 1943 an Allied Combined Communications Board, or CCB, found that the security limitations of Eureka's five fixed frequencies posed no long-term security vulnerability by concluding, incorrectly, that the Eureka would only be employed "until something better is available." (24)

The following month, a joint U.S. Army-Navy radio frequency coordination meeting essentially agreed with the CCB, but for a different reason. When a U.S. Navy representative found that two of the Eureka's frequencies overlapped those allocated to a future communications system, he dismissed the issue stating, the "Eureka would be abandoned in about a year because of the advantage with which it can be used by the enemy." (25) The implication was that either a Eureka beacon could be too easily captured and turned back against Allied forces, or that the Eureka's fixed frequency allocation would be soon discovered and emitted back on enemy countermeasure systems, thereby confusing the Eureka or Rebecca components. A weakness in OSS and SOE security policy would later compound this problem. In December 1944, OSS air operations personnel adopted a British practice employed in Italy and Yugoslavia that used only two of the Eureka-Rebecca frequencies (214 Mc/Sec & 219 Mc/Sec). It was thought these two channels worked the best, and nearly twenty OSS teams sent into northern Italy carried Eureka beacons confined to these two frequencies. If German intelligence captured one of these sets (as they did, to be discussed later) they could deduce the Eureka frequencies used by most of the OSS teams in Italy. (26)

Perhaps to minimize the vulnerability of the Eureka's fixed frequencies, the U.S. Eurekas did feature a "Morse" key. The key interrupted Eureka transmissions in short bursts that visually simulated international Morse code on the Rebecca's radar screen. War Department manuals issued with each Eureka set officially advocated use of the Morse key feature so that aircrew monitoring the Rebecca screen could discern different Eureka sets that might be in close proximity. After the war, however, MIT suggested that the Signal Corps added the Morse key feature to prevent enemy manipulation of the Eureka; for the enemy to credibly playback a captured Eureka, they would need to know a one or two letter Morse code assigned to that particular mission. Perhaps lending weight to the latter concern, all U.S. Eurekas adopted the British inclusion of a self-destruct detonation system to insure against the beacon's capture. (27)

In 1943 the OSS sent their first Eureka-Rebecca shipments overseas. Early on, these shipments accompanied classified cipher equipment, transported by air and protected by armed guard. By 1944, however, trucks delivered Eureka beacons from the OSS Northern Virginia warehouse to Baltimore Harbor, and paper receipts alone tracked Eureka shipments by sea to Europe, the Mediterranean, and India. The OSS continued to track Eurekas within these theaters, including their use behind enemy lines. (28) Once Eureka sets arrived in theater, special operations training policy required that OSS, SOE, and SAS teams receive training on their use. By June 1944, SOE determined that whereas the new and more simply designed Eureka models required only a one-hour lecture, agents also needed practical field instruction. (29) That year SOE instituted a ten-day DZ "reception committee" school in England. Among other topics, the school covered the clandestine "S-Phone" for ground to air voice communication, DZ ground lighting patterns and Morse flashlight signals to aid navigation and provide security confirmation for approaching aircraft, and it allocated three days for Eureka instruction and hands-on operation. Security instruction for the beacon took forty-five minutes, and presumably covered Eureka's low-probability of intercept, Morse key feature, and the set's self-destruction mechanism. (30) OSS personnel in England also attended this school, but OSS commands elsewhere had to develop their own DZ training for both American OSS and foreign national agents. OSS radio experts in Italy, for example, found the Eureka beacon to be a simple device upon which to train American students, but they had little guidance about the appropriateness of instructing their Italian agents on the classified beacon. Nevertheless, they correctly assumed that training foreign agents to use the Eureka would correspond with any existing policy on the matter. As a final precaution, the OSS issued a certificate to each team receiving a Eureka beacon. The certificate required that "precautions be taken to prevent compromise of the beacon," and if a team had to destroy their beacon, they were to radio the event to their OSS base. (31)

OSS DZ policy based the operational security of the Eureka upon the safety of the DZ perimeter, and this policy required what was in practice an optimistic ten mile Eureka operating distance from known enemy positions. (32) But a promising new concept called "blind use" of the Eureka soon complicated this conservative approach to DZ security. In December 1944, an OSS air operations officer in Italy found that the pinpoint accuracy of the Eureka at night often did not require supplemental navigational assistance for an approaching aircraft, typically in the form of DZ ground fire patterns or Morse code flashlight signals, practices that could draw enemy attention. Eliminating these visual aides gave greater cover to clandestine DZ operations, but also sacrificed important visual signals that gave final security confirmation that the DZ was in friendly hands. Yet word of "blind use" accuracy arrived in London, where SOE expressed interest in the procedure as late as April 1945. (33) During this same period, however, the U.S. AAF informed OSS air operations personnel that AAF navigators monitoring their Rebecca radar screens were having difficulty deciphering the Eureka's Morse code transmissions. Unlike audible Morse radio transmissions, Morse codes keyed through the Eureka beacon had to be viewed as pulses on the Rebecca's three-inch diameter radar screen, where transmission speed on the Eureka key compounded the navigators' sight limitations using the small screen. Difficulties monitoring Morse transmissions on Rebecca, together with mounting reports that Eureka operators on the ground were apparently tiring of the beacon's Morse keying requirement, may explain why Morse key security for the Eureka-Rebecca system fell into disuse on both ends of the system; and this at a time when "blind use," having already dispensed with the ground fire patterns and Morse flashlight signal security checks, would seem to demand its use. (34)

An agent could jump with a Eureka beacon attached to his parachute harness or, as was often the case, special operations commands could parachute Eurekas in supply containers to agent teams upon request by radio. The most common cause of lost Eurekas occurred during night DZ supply drops. Mis-dropped containers and high winds routinely dispersed supplies, and references to accidental Eureka losses are prevalent in OSS, SOE, and SAS radio messages and after-action reports. (35) Radio messages also show the efforts made to keep the Eureka-Rebecca system out of German hands. One French resistance group had no choice but to search for hours, only 1,000 yards from a large German encampment, for their miss-dropped Eureka. (36) Almost a year later in Norway, after OSS Major William Colby searched the wreckage of a crashed OSS transport aircraft, he radioed his report to England and, at the end of the message, confirmed that the aircraft's Rebecca had been destroyed in the crash, an observation apparently made to ensure that the Rebecca was of no use to the Germans. (37) Despite these precautions, apparent examples of late-war losses of Eureka beacons to the enemy resulted from the capture of OSS Team Dawes by the SS in Czechoslovakia; from the capture of OSS Operational Group Tacoma by the SS in northern Italy; and from the apparent discovery of OSS Operational Group Battle's hidden radio equipment and Eureka by Cossacks on the Italian-Slovenian border. (38) At the same time these teams were operational, U.S. AAF navigators on OSS supply missions to northern Italy carried special pre-printed forms to record Eureka-Rebecca performance. In late February, one particular navigator could not find the Eureka "blip" on his Rebecca screen when expected. He noted on his Eureka-Rebecca form, however, that during the mission he "picked up several [blips] but they all run up & down the trace line." He appeared to be receiving multiple Eureka signals from the ground where there should have been none. (39)

German Intelligence and the Eureka-Rebecca System

OSS debriefs filed after the war by members of a captured OSS Operational Group team reveal that their German interrogators knew much about the OSS command structure in Italy. As Operational Group Tacoma's radio operator later said of his interrogation by an SS officer, "they knew more than I did about the outfit." He added that before his interrogation, the SS officer placed his two OSS radios and Eureka radar beacon on a table in front of him, in an apparent mocking gesture. (40) Berlin destroyed a large portion of its intelligence records at the end of the war, but those remaining documents suggest that German intelligence organizations possessed a sound understanding of Allied special operations. For example, Berlin knew the location of many OSS training schools and bases in England and Italy, the names of pertinent OSS officers and instructors, and even understood the basic operation of the OSS special operations airbase in Harrington, England. (41) The Germans also captured large numbers of Allied equipment containers parachuted behind their lines. The loss of equipment was seemingly so extensive that one SOE agent captured in Paris noted, in his postwar memoir, a pile of captured parachuted equipment containers so large it was impossible to ignore as he was led into the Abwehr's Paris headquarters. (42)

Once German counterintelligence located special operations DZs, they would either monitor agent and reception committee activities at those sites, or destroy the DZs immediately. One method employed to eliminate DZs, and at the same time spread skepticism within the ranks of the local resistance forces, was to parachute German agents onto known DZs. In July 1944, the local French resistance informed Operational Group Louise that only a few days earlier Germans, dressed in American uniforms, had jumped on Louise's DZ in an attempt to surprise and destroy the French reception committee. (43) And in Italy, OSS teams radioed their commands that Germans were manning false DZs using routine ground signals, and possibly using captured agent radios to arrange the drops. (44) Berlin employed other methods as well. The Abwehr attempted to track special operations flights from England to western Europe in order to estimate the location of Allied DZs, and the amount of supplies and agent teams dropped in those areas. Through a combination of radio intercepts and radar intercepts of lone aircraft, to routine flight sightings passed to the pertinent Abwehr offices, they could extrapolate special operations flight data. (45)

German policy directed that captured "novel or technically improved" radio devices be forwarded to the appropriate technical intelligence office, unless an impending radio game required their use. Luftwaffe intelligence (OKL Ic) remained the primary authority for the collection and dissemination of information associated with Allied aircraft, and this included the Eureka-Rebecca system. (46) The first German publication informing front-line intelligence units of Eureka beacon specifications was an OKL Ic weekly intelligence newsletter, titled Einzelnachrichten des Ic Dienstes West ("Special Intelligence of Intelligence Service West," hereafter referred to as Einzelnachrichten). The first edition of Einzelnachrichten to include the Eureka appeared on June 19, 1944, only two weeks after Allied airborne units used the Eureka to guide paratroopers to their DZs behind the Normandy beaches. The newsletter described the Eureka's purpose, range, and details such as its Morse key feature. Einzelnachrichten added the following month that OKL Ic had not observed the use of a Eureka by "regular" airborne units until the Normandy landings. (47) In August 1944, the newsletter carried a special edition on Allied special forces operating on the European continent, and repeated the Eureka's purpose as a key special operations device; it included a diagram of the Eureka, and closely associated the device with the SAS, an observation perhaps driven by previously referenced SAS Eureka losses in France during June 1944. (48) In October, Einzelachrichten included the specifications of the overall Eureka-Rebecca system, and summarized that "up until now, the total assessment of this system had not been settled." Perhaps the exploitation of the early Eureka-Rebecca devices captured by the Abwehr's Major Giskes during 1942 and 1943 remained incomplete; or perhaps the alleged inability of Berlin's many intelligence services to effectively exchange information is at fault. (49)

Nevertheless, radio messages sent between a Eureka-equipped special operations team in France and its London headquarters appear to indicate an instance where the Luftwaffe assisted German intelligence to counter the Eureka-Rebecca system. On June 5, 1944 an Allied special forces "Jedburgh" team, codenamed Hugh parachuted into the Indre region of France. Special Forces Headquarters (SFHQ) in London conceived of the three-man Jedburgh teams to serve as a joint American, British and Free French liaison to the French resistance, and to work with other special forces units, such as the SAS and the OSS Operational Groups. Jedburgh team Hugh was to work closely with SAS team Bullbasket. Bullbasket had parachuted into the same area on June 7, having lost their Eureka container during the jump. Three weeks later, Jedburgh team Hugh radioed SFHQ to inquire about what Hugh assumed were Allied planes circling in the proximity of its DZ. SFHQ, however, had not send any supply aircraft to the area, and responded in radio code to Hugh:

Have no idea whose planes circled ... night 25/6 but believe Boche may have Eurekas and have located these areas in this way Hugh to advise immediately if he would prefer to postpone operation until he finds another ground. (50)

SAS Eureka container losses in June 1944 could have found their way into German hands. The Eureka's preset frequencies would have allowed Luftwaffe aircraft to patrol suspected areas, emit those frequencies on German radio systems modified to mimic the Rebecca component, and possibly prompt Eureka beacons in the area to identify the direction to enemy DZs.

About two months following the September 1944 Allied airborne landings in Holland, Einzel-nachrichten contained a special feature subtitled "New Discoveries about the Employment of Allied Parachute and Air-Landing Troops." In this issue, OKL Ic charted known Eureka beacon locations used during the airborne operation in Holland, and also suspected Eureka beacon locations in England, where the beacons aided conventional air traffic control for the hundreds of Allied C-47 aircraft flying towards Holland from their English airbases. (51) It was during this period that Berlin considered an unusual countermeasure to Allied radar beacon sites. Before the Normandy landings, the Allies had delivered Eureka beacons to European resistance groups with instructions to align the beacons in a direction that would provide discrete navigation tracks for Allied bombers heading to their targets in Germany. (52) After the invasion, the Allies were able to move larger and more powerful conventional radar navigation systems to liberated regions of France and Belgium for the same purpose. In October 1944, OKL Ic met with its own reconnaissance liaison officers and with representatives of SS Lt. Colonel Otto Skorzeny's commando organization. They apparently reached an agreement for the OKL Ic to determine the location of Allied radar navigation beacons in France and Belgium, and pass those locations to Skorzeny's unit. The commandos would then, as they termed it, "clean out" the located beacon sites, possibly giving German cities and military facilities a respite from Allied bombings. Apparently, nothing came of the meeting, but by the standards reached there, any known Eureka beacon sites would have been included on Skorzeny's target list. (53) The SS also distributed a directive that included countermeasures against the Eureka. In January 1945, the Gestapo issued detailed instructions to SS police and SS radio intelligence technicians regarding radio countermeasures to SAS operations. Recommended countermeasures to SAS radios centered upon employing electronic direction-finding tactics against the radios; the thinking here, it appears, was that if direction-finding proved successful against SAS radios, Eureka beacons in SAS possession would be captured along with the radio sets. (54)

By the end of 1944, Berlin had consolidated all Allied radar information of interest within the Reichsluftfahrtministerium (RLM, or National Air Ministry). The RLM served as Germany's central office for aviation matters, and it collected information on many Allied radar systems, including details on the Eureka-Rebecca frequency spectrum. It concluded that the success of using captured Eureka beacons to deceive Allied special operations, while possible, could not be "guaranteed" because of the Eureka's Morse key security feature. The RLM suggested instead that the continuous interrogation of Rebecca, by ground-based German radio jammers emitting known Eureka frequencies, could flood the Rebecca receiver with false signals. Under these conditions, airborne Rebecca systems could be rendered incapable of establishing a navigation link to the proper Eureka beacon. Because of this vulnerability, the RLM concluded that Rebecca was "jammable." (55)

Conclusion

In December 1944, the OSS officer responsible for managing all U.S. Eurekas sent into northern Italy summed up the beacon's security against electronic countermeasures this way:

The Eureka is not subject to DF [direction finding] operations by the enemy insofar as is known. Its ultrahigh frequency makes such measures impractical by other than exact simulation of the Rebecca equipment of the plane, which while possible is not considered to be within the enemy's capabilities at present. (56)

There is anecdotal evidence that the Luftwaffe did attempt to locate Allied special operations DZs by using German aircraft systems to simulate Eureka-Rebecca frequencies to trigger Eureka beacons; or, at least, the suspicious activity of German patrol aircraft caused SFHQ in London to radio special operations personnel in France that the Germans were somehow exploiting captured Eurekas. Berlin also identified methods to counter the Eureka, outside of traditional direction-finding techniques. German radar experts determined that, by flooding the skies over known areas of Allied special operations with the proper frequencies, they could in theory prevent Rebecca-equipped aircraft from establishing the correct navigation link to their DZs, thereby denying Allied reinforcement and resupply for special operations.

German intelligence for the most part, however, may have approached this task in a more practical manner. As early as 1942, the Abwehr's direct manipulation of captured Eureka beacons helped to build a foundation for the capture of substantial numbers of special operations personnel. (57) Whether or not the assumption of Berlin's continued manipulation of the Eureka until the end of the war is accepted, this one method of deception could claim its place as a ruse used in the wider deception against Allied intelligence--the capture and exploitation of special operations teams and clandestine agents. The playback of captured radio transmitters could seriously mislead Allied commands into believing that their special operations were secure and active, when in fact many of the radio messages received by Allied headquarters were deceptive radio games managed by German counterintelligence. The compromise of the Eureka-Rebecca system sometimes played an integral part in this deception.

NOTES

(1.) A short summary of the postwar investigation of SOE's Holland compromises can be found Nigel West, Secret War: The Story of SOE, Britain's Wartime Sabotage Organization (London: Hodder & Stoughton, 1992), 99-101.

(2.) Armeeoberkommando I/Ic, Appearance of S.A.S. Troops in the Army Area [OSS translation], November 1944, RG 226, Entry 190, Box 292, Folder 1350. This folder contains correspondence relating to Gubbins' inquiry.

(3.) This paper draws from three main sources in the US National Archives & Records Administration (NARA): Record Group (RG) 226--Records of the Office of Strategic Services; RG 111--Records of the Office of the Chief Signal Officer (US Army); and the Captured German Records Collection on microfilm. OSS and Signal Corps record locations are cited by RG #, Entry #, Box #, and Folder # or title. German records are identified by "T" microfilm series #, Roll #, and Frame #. RG 226 and RG 111 also contain related British reports received by the OSS and U.S. Signal Corps. The growing volume of WW II special operations literature often cites the extensive use of the Eureka beacon. Examples are Ian Wellsted, SAS With the Maquis (London: Greenhill Books, 1994); Bruce Heimark, The OSS Norwegian Special Operations Group in WW H (Westport, Ct.: Praeger, 1994); Gerald Schwab, OSS Agents in Hitler's Heartland (Westport, Ct.: Praeger, 1996); Paul McCue, SAS Operation Bulbasket (London: Leo Cooper, 1996); Freddie Clark, Agents by Moonlight: The Secret History of RAF Tempsford During World War II (Charleston, S.C.: Tempus Publishing Inc., 1999); Thomas Nielsen, Inside Fortress Norway: Bjorn West--Norwegian Guerilla Base, 1944-1945 (Kansas: Sunflower University Press, 2000); M.R.D. Foot, SOE in the Low Countries (London: St. Ermin's Press, 2001); and William Mackenzie, The Secret History of SOE: The Special Operations Executive 1940-1945 (2000; reprint, with a foreword by M. R. D. Foot, London: St. Ermin's Press, 2002).

(4.) For example, in January 1945 the OSS London office only made local distribution of the aforementioned German directive, and the document apparently failed to draw attention to German familiarity with the Eureka radar beacon.

(5.) The impact of successful German radio games in Western Europe can be found in many histories of WW II special operations. One detailed account is in West, Secret War: The Story of SOE, Britain's Wartime Sabotage Organization, 88-104.

(6.) Arthur Roberts, ed., Radar Beacons (New York: McGraw-Hill, 1947), 10-11. "Radar" is an acronym for radio detection and ranging, as it allows the determination of both location and distance. The word "radar" remained restricted until June 1943, when the Allies released the term to the public. See Louis Brown, A Radar History of World War II: Technical and Military Imperatives (Bristol: Institute of Physics Publishing, 1999), 381.

(7.) Callum MacDonald, The Killing of SS Obergruppenfuehrer Reinhard Heydrich (New York: The Free Press, 1989), 151-52, 154. SOE-trained Czech teams such as Out Distance represented Czech President Benes' exiled government in London.

(8.) Heydrich to Reichsleiter Martin Bormann, Ereignismeldung an den Fuehrer ueber Herrn Reichsleiter Bormann, 4 May 1942, T-84, Roll 437, Frames 122-25. Also see MacDonald, The Killing of SS Obergruppenfuehrer Reinhard Heydrich, 154. One surviving member of Out Distance went on to contact another Czech team, Anthropoid, which on 27 May 1942 assassinated Reinhard Heydrich.

(9.) H.J. Giskes, London Calling North Pole (London: William Kimber, 1953), passim. The collapse of the Holland network is found in the official secret history of SOE, recently declassified. See Mackenzie, The Secret History of SOE.

(10.) Giskes, London Calling North Pole, 102.

(11.) Ibid., 102.

(12.) In October 1943, two Dutch agents escaped German captivity and informed SOE of the German deception. One of their autobiographies is by Pieter Dourlein, Inside North Pole: A Secret Agent's Story (London: William Kimber, 1954). Regarding the Czech teams, London deduced their end through lack of initial radio contact, failed German "radio games" with captured radio sets, and through German propaganda. For example, see MacDonald, The Killing of SS Obergruppenfuehrer Reinhard Heydrich, 196, 207.

(13.) SOE compartmentalized its operations for security reasons. So, or example, the French section did not know of compromises within the Dutch section. See M. R. D. Foot, SOE in France: An Account of the Work of the British Special Operations Executive in France 1940-1944 (London: Her Majesties Stationary Office, 1966), 343-44. Security compartmentalization also disallowed the exchange of London's intercepted and deciphered Abwehr and SD radio traffic--transmissions that might have suggested Abwehr or SD penetration of Allied clandestine operations. See the official history by John Curry, The Security Service 1908-1945: An Official History, with an introduction by Christopher Andrew (Kew: Public Record Office, 1999), 209.

(14.) Lt. Col. Magee, US Army Signal Corps, Procurement of British Rebecca Equipment, 23 October 1942, RG 111, Entry 1024, Box 1533, Folder "AN/PPN-2, Part 2 of 2." TRE training is cited in TRE Great Malvern, Progress Report for the Period 16th September to 15th October 1942 [British report], Secret, 19 November 1942, RG 111, Entry 1024, Box 1743, Folder "Br. Equipment Reports."

(15.) Carleton S. Coon, A North Africa Story: The Anthropologist as OSS Agent 1941-1943 (Ipswich, Mass.: Gambit, 1980), 39.

(16.) Capt. Browne to Col. Donovan, Memo w/attachment, Secret, 15 December 1942; Maj. Lowman to Lt. Graveson, Memo, Secret, 11 January 1943; and Maj. Lowman to Col. Donovan, Memo, Secret, 11 January 1943, RG 226, Entry 146, Box 163, Folder 2414.

(17.) Capt. Browne to Lt. Col. Roberts, 12th Air Force, Memo, Secret, 14 December 1942, RG 226, Entry 146, Box 163, Folder 2414.

(18.) Undated OSS cable # 101750, RG 226, Entry 136, Box 1, Folder 8. This cable shows that Washington asked the Spanish government to "guard" the interned American aircraft. This was a dubious precaution, as the Allies would later take advantage of Madrid's known links with the German Abwehr in a Top Secret operation called Mincemeat. In 1943, Operation Mincemeat planted misleading information about Allied Mediterranean strategy into the hands of Spanish intelligence officers who, as expected, forwarded it to the Abwehr. This deception successfully diverted Berlin's attention away from the Allies' planned objective of Sicily. See Ewen Montagu, The Man Who Never Was (Philadelphia: J.B. Lippencott Co., 1954).

(19.) Giskes, London Calling North Pole, 121. Accounts of even earlier compromises of a baseline Rebecca system can be found in Brown, A Radar History of World War II, 338. Brown's text covers the overall radar countermeasures "war" between the Allies and Axis. TRE's admitted risk in adding what it called "the special secrecy" of the Rebecca counterpart to conventional bomber navigation suites is in TRE Report, No. 1486 [British Report], Most Secret, 27 June 1943, p. 3, RG 111, Entry 1024, Box 1725, Folder "RB-413.44 RB-1891 IFF MK V."

(20.) Capt. Ogas, IFF Section, US Signal Corps, Performance Tests of AN/APN-2 and AN/PPN-1, Secret, 5 February 1944, RG 111, Entry 1024, Box 1735, Folder "Beacons." Compromises of Mk III IFF are found in Office of the Chief Signal Officer, Airborne Monthly Report for November and December 1943, Secret, 10 February 1944, and Col. Unruh, Air Corps, I.F.F. Triggering by Japanese Night Fighters, Secret, 30 October 1943, RG 111, Entry 1024, Box 1542, Folder "RB 413.44, Ident. #13, part 2 of 2." See also New Zealand intelligence report on Japanese electronic countermeasures against Allied radar in the Northern Solomons, in Maj. Watson-Munro, Report on R.C.M. in Bougainville Area, Secret, 29 January 1944, RG 111, Entry 1024, Box 1542, Folder "RB 413.44, Ident. #13, part 3 of 3."

(21.) Jennet Conant, Tuxedo Park: A Wall Street Tycoon and the Secret Palace of Science That Changed the Course of World War II (New York: Simon & Schuster, 2002), passim. Stimson's cousin, Alfred Loomis, established the Rad Lab at MIT. MIT, under the direction of the U.S. National Defense Research Committee, helped the War Department assess the feasibility of integrating the British Eureka design with U.S. radar production technology. The Signal Corps' Camp Evans Signal Laboratory in New Jersey then contracted with U.S. industry for the manufacture of thousands of "AN/PPN-1" and "AN/PPN-2" Eureka radar beacons. "AN/PPN" was standardized U.S. nomenclature for "Army-Navy/Man Portable-Radar-Navigation." The AN/PPN-1 & 2 would be employed by regular airborne divisions and the OSS. The United Kingdom, through international aid, received nearly 50% of total U.S. production. Signal Corps correspondence for the initial Eureka procurement phase (January-April 1943) is found in RG 111, Entry 1024, Boxes 1533, 1732, & 1770.

(22.) Thomas F. Troy, ed., Wartime Washington: The Secret OSS Journal of James Grafton Rogers 1942-1943 (Frederick, Md.: University Publications of America, Inc., 1987), 180.

(23.) An AAF transcript for a training film on the Eureka stated that the five assigned frequencies were "enough for security." See 18th AAF Base Unit, Rebecca-Eureka Project 1931, Confidential, 19 December 1944, RG 226, Microfilm Series 1642, Roll 47, Frame 848.

(24.) The Allied Combined Chiefs of Staff Combined Communications Board coordinated the frequency allocation of Allied radio and radar systems to avoid frequency overlap and system interference. The CCB also assessed the Eureka's frequencies. See the Combined Chiefs of Staff, Combined Communications Board (CCB), Minutes, 9 April 1943, RG 111, Entry 1024, Box 1119, Folder 334.

(25.) E. M. Roberts, Airborne Section, Office of the Chief Signal Officer, Proposed Radio Spectrum Allocations, Secret, 5 May 1943, RG 111, Entry 1024, Box 1769, Folder "RB413.44 RB-2032 Airborne Radar Equipment #2 (2 of 2)."

(26.) See Lt. J. J. Orlan, 2677th Regiment, OSS, Eureka Operations, Secret, 2 December 1944; Lt. Orlan, 2677th Regiment, OSS, Untitled Eureka Morse Code Plan, Secret, 4 December 1944; and Lt. B. M. Cave to Maj. J. Duncan, 2677th Regiment, OSS, Eurekas in the Field, 11 January 1945. All three documents are located in RG 226, Entry 190, Box 96, Folder 91.

(27.) War Department operating manuals for the U.S. Eureka models are TM 11-1140, Responder-Beacon AN/PPN-1, Confidential, 12 July 1943; TM 11-1140A, Beacon Transmitter-Receiver AN / PPN-1A, Confidential, 10 May 1944; and TM 11-1145, Beacon Transmitter-Receiver AN/PPN-2, Confidential, 19 August 1944. MIT assessment of the Morse key feature is in Roberts, ed., Radar Beacons, 11. Regarding the Eureka's self-destruct system, see G. H. McClurg, Office of the Chief Signal Officer, Conference on Eureka Mk III, Secret, 22 February 1943, RG 111, Entry 1024, Box 1533, Folder "AN/PPN-1 Part 2 of 2." London recommended detonators for the new Eureka models, and first considered installation of detonators in November 1942, about six months after the first compromises in Czechoslovakia and Holland. See TRE Great Malvern, Progress Report for the Period 16th September to 15th October 1942 [British report], Secret, 19 November 1942, RG 111, Entry 1024, Box 1743, Folder "Br. Equipment Reports."

(28.) OSS Message, 12 August 1943, RG 226, Entry 134, Box 211, Folder 1319. Some Eurekas, nevertheless, were lost in shipment. See List, Boxes Missing-Algiers Shipment, 26 October 1944, RG 226, Entry 135, Box 50, Folder 543. Routine OSS shipping receipts from Baltimore to overseas commands are in RG 226, Entry 135, Boxes 543 & 555. Records of the 2677th Regiment, OSS, (Italy) tracking by serial number their Eurekas behind enemy lines are found in RG 226, Entry 1190, Box 96, Folder 91. OSS London also tracked Eurekas in France. For example, see OSS Jedburgh Team Hugh, Radio Message to London, 14 June 1944, RG 226, Entry 103, Box 3, Folder 82.

(29.) Minutes of Special Forces Headquarters, Secret, 8 June 1944, RG 226, Entry 190, Box 357, Folder 357.

(30.) OSS also used SOE's ten-day reception committee school. See Maj. C. A. Pitre, Chief, Training Program, OSS/SO Branch, Final Progress Report for period 1-9 December 1944, RG 226, Entry 92, Box 549, Folder 19.

(31.) Lt. Orlan, 2677th Regiment, OSS, Memo, Eureka Operations, 17 November 1944, RG 226, Entry 190, Box 96, Folder 91; and OSS Communications Office, to Lt. Cave, 2677th Regiment, OSS, Message, 17 December 1944, RG 226, Entry 190, Box 96, Folder 91. OSS commands remained unaware that in September 1944 the CCB had approved the release of all radar beacon technology to each member of the Alliance including resistance groups. See Maj. Gen. J. A. Ulio, Policy on Release of Radar Equipment and Information, Secret, 22 September 1944, RG 111, Entry 1024, Box 1528, Folder "Radar Equipment # 9, Part 2 of 2." Eureka destruction certificates for the 2677th Regiment, OSS, are located in RG 226, Entry 190, Box 96, Folder 91.

(32.) Lt. F. McDonough, 2677th Regiment, OSS, Request for Eureka Equipment, Secret, 16 November 1944, RG 226, Entry 190, Box 96, Folder 91, and Lt. H. H. Proctor, OSS SI Branch London to Lt. Col. K. T. Downs, Air Dispatch, Secret, 17 May 1944, RG 226, Entry 190, Box 290, Folder 1283.

(33.) Lt. Cave to Maj. V. A. Abrignani, 2677th Regiment, OSS, Memo, 18 December 1944, RG 226, Entry 190, Box 96, Folder 91; Lt. Cave, 2677th Regiment, OSS, Special Operations Memorandum: Air Supply Operations, Secret, 25 February 1945, RG 226, Entry 190, Box 93, Folder 66; Lt. Cave to Maj. C. J. Eubank, 2677th Regiment, OSS, Eurekas, Secret, 2 March 1945, RG 226, Entry 190, Box 96, Folder 91; and SOE report, D/BT's Progress Report for April, 1945, RG 226, Entry 148, Box 84, Folder 1220.

(34.) In August 1944, TM11-1145, Beacon Transmitter-Receiver AN/PPN-2, 37, first highlighted the lack of Eureka Morse key use. The problem also surfaced in late-War Italy. See Lt. Cave to Maj. Eubank, 2677th Regiment, OSS, Eurekas, 2 March 1945, RG 226, Entry 190, Box 96, Folder 91.

(35.) Lost container reports are found throughout special forces Jedburgh aider-action reports located in RG 226, Entry 103, Boxes 1-4. SAS Eureka container losses in France during June 1944 are cited in Maj. O. A. Elwes, Report on Operation Lost, Secret, June 1944, RG 226, Entry 190, Box 328, Folder 7; Wellsted, SAS With the Maquis, 50; and McCue, SAS Operation Bulbasket, 25.

(36.) Jedburgh Team Gerald After-Action Report, 18 July 1944, RG 226, Entry 103, Box 3, Folder 46.

(37.) Maj. William E. Colby, Norso Operational Group, OSS to Lt. Col. H. H. Skabo, Scandinavian Section, OSS/SO, Burial of Personnel of Plane Jones, Secret, 30 April 1945, RG 226, Entry 115, Box 51, Folder 654. During the 1970's, Colby would head the Central Intelligence Agency (CIA).

(38.) Reference to Dawes' capture and their use of a Eureka is in Dawes to OSS Base Caserta, Radio Message, 22 October 1944, RG 226, Entry 154, Box 42, Folder 642; and OSS Base Bari to OSS Base Caserta, Radio Message, Secret, 2 February 1945, RG 226, Entry 154, Box 42, Folder 642. Tacoma's loss of their Eureka to the SS is in a postwar debrief by Tacoma's radio operator. See Cpl. O. M. Silsby, Company A, 2671st Special Reconnaissance Battalion, OSS, Report of the Tacoma Mission, n.d. [approximately July 1945], RG 226, Entry 143, Box 11, Folder 145. Loss of Battle's equipment is in G. M. Proctor, 2677th Regiment, OSS, to Commanding General, HQ, MATAF, Eureka, Secret, 19 March 1945, RG 226, Entry 190, Box 96, Folder 91; and in OSS Operational Group Battle to 2677th Regiment, OSS, Radio Message, 7 April 1945, RG 226, Entry 190, Box 160, Folder 1109.

(39.) Lt. Shanklin, 35th Squadron, 51st Troop Carrier Wing, U.S. AAF, Radar Report for Missions, Secret, 26 February 1945, RG 226, Entry 190, Box 96, Folder 91.

(40.) Cpl. Silsby, Report of the Tacoma Mission, RG 226, Entry 143, Box 11, Folder 145.

(41.) Der Reichsfuehrer SS Reichssicherheitshauptamt, Amt IV Gr. 4 B, Agenten u Sabotageschulen Der Feindlaender, Geheim, 13 June 1944 [reissue of Oberkommando der Wehrmacht (OKW) Amt Abwehr, Abt.Abw.III, 19 April 1944], T-77, Roll 1503, frames 14-38; and Oberkommando des Heeres, Fremde Heere West, Organisation die amerikanischen N.D., 5 December 1944, T-78, Roll 705 Frames 43-58. After the war an OSS report stated, "the Germans knew all about the Harrington Group and what it was doing." See OSS Operations Report, DIP, SI, ETO, Division of Intelligence Procurement, Air Operations Section Final Report, 7 June 1945, Secret, RG 226, Entry 146, Box 230, Folder 3245.

(42.) Guido Zembsch-Schrieve, Pierre Lalande: Special Agent, trans. John Brownjohn (London: Leo Cooper, 1996), 120. An OSS-compiled history estimated that Germans captured 15-20% of supplies dropped into France. See OSS Aid to the French Resistance in World War H, undated, RG 226, Entry 190, Box 241, Folder 1. Many of the captured containers contained radio equipment. See Abwehr III F West, Increased dropping of enemy agents, arms, ammunition, and explosives on occupied French territory [OSS translation], Secret, 8 March 1944, RG 226, Entry 190, Box 292, Folder 1350.

(43.) Operational Group Louise Operational Report, Company "B" 2671st Special Reconnaissance Battalion Separate, (Prov.), Grenoble, France, 20 September 1944, Secret, RG 226, Entry 154, Box 162, Folder 2770.

(44.) OSS Team Lobo to OSS Base Florence, Radio Message, Secret, 5 March 1945, RG 226, Entry 190, Box 158, Folder 1089; OSS Operational Group Battle to 2677th Regiment, OSS, Radio Message, Secret, 18 April 1945, RG 226, Entry 190, Box 160, Folder 1109; and OSS Capt. Jules Konig to HQ Co. A 2677th Regiment, OSS, Interrogation of Johann Sanitzer, Confidential, 30 June 1945, RG 226, Entry 124, Box 26, Folder 194. By 1944, German intelligence recognized established Signal Corps ground to air signal patterns, and other supply procedures down to the color-codes of supply parachutes. See the series of 1943 and 1944 German Airforce intelligence reports by Fuehrungsstabe Ic, Fremde Luftwaffen West, Einzelnachrichten des Ic Dienstes West and G.B.-US.A. Fallschirm-und Luftlandetruppen, in T-321, Rolls 98-102.

(45.) Oberstleutnant Reile, OKW, Leitstelle Abwehr III West an Verteiler, Einfluege feindlicher Spezialistenflugzeuge im Monat Maerz 44, Geheim, 3 May 1944 and Einfluege feindlicher Spezialistenflugzeuge im Monat April 44, Geheim, 4 June 1944, T-77, Roll 1515, No Frame #s. This paper cites those few pertinent intelligence documents that escaped destruction by Berlin's intelligence services. A review of the subject indices of intercepted Abwehr message traffic, located in the United Kingdom's Public Records Office, does not suggest the presence of deciphered Abwehr messages on details such as the Eureka beacon.

(46.) OKW, WFST/A.Ausl.Abw./Abt.Abw.III/I/Ag WNV/ Fu, Behandlung vor erbeutetem Agenten-Funkgeraet und Funkbetriebsunterlagen, Geheime Kommandosache, 14 April 1943, T-175, Roll 404, Frames 2926931-940. The SS issued similar instructions. See Chef der Sicherheitspolizei, Sichergestellte Waffen, Munition und Sabotagemittel, Geheim, 15 September 1943, T-175, Roll 254, Frames 2746880-882; and SS Pz. Div. "Das Reich," Agenten-Kleinfunkgeraete, 26 June 1944 [reissue of "Panzergruppe West" 22 April 1944 directive], T-354, Roll 129, Frames 3765843-844. For Luftwaffe authority, see OKL, Fuehrungstabe IC, Vorschrift fuer die Sicherung yon Luftwaffengefangenen Beutepapieren und Beutegeraet, 31 October 1944, T-283, Roll 75, Frames 4575237-254.

(47.) OKL Ic, Einzelnachrichten des Ic Dienstes West der Luftwaffe, Nr 55, Geheim, 19 June 1944, T-321, Roll 1001, Frame 651; and Einzelnachrichten des Ic Dienstes West der Luftwaffe, Nr 60, Geheim, 7 July 1944, T-321, Roll 101, Frame 737.

(48.) Einzelnachrichten, Nr. 62, Geheim, 15 August 1944, T-321, Roll 101, Frames 767-790.

(49.) Einzelnachrichten, Nr. 76, Geheim, 8 October 1944, T-321, Roll 101, Frame 1074. On Berlin's many competing intelligence services, see David Kahn, Hitler's Spies: German Military Intelligence in World War H (New York: Macmillan Publishing Company, 1978), passim. Kahn also addresses intelligence exchanges between Berlin and Tokyo, and it is possible that Japan received routine radio and radar countermeasure information collected by Berlin. Examples of German radar technology passed to Tokyo are in Brown, A Radar History of World War H, 135-40.

(50.) SFHQ Staff Report, Cipher, 28 June 1944, Vol. I, June 6th-30th 1944, 45-50, RG 226, Entry 103, Box 2, Folder 5. Bullbasket's lost Eureka is in McCue, SAS Operation Bullbasket, 25.

(51.) Einzelnachrichten, Nr. 80, Geheim, 18 November 1944, T-321, Roll 225, No Frame #s.

(52.) For an example of the use of "fixed" Eureka sites, see Clark, Agents By Moonlight: The Secret History of RAF Tempsford During World War H, 221. Clark refers to the ground-based Eureka as "Rebecca."

(53.) OKL Ic, Vernichtung yon besonders wichtigen Bodenstellen feindlicher UKW Navigations-und Zielfindungsverfahren durch Sabotage-Trupps des RSHA, Geheime Kommandosache, 24 October 1944, T-321, Roll 100, Frames 195-202. Among the Allied radio and radar beacon systems Berlin targeted were the larger "Gee" and "Oboe" stations moved to Europe after the Normandy landings. These powerful systems provided navigation aid for Allied bombers. See Brown, A Radar History of World War II, 322.

(54.) SS-Gruppenfuehrer Mueller, Reichssicherheitshauptamt, Einsatz von Einheiten des britishehen Special Air Service (SAS), Geheim, 23 January 1945, T-175, Roll 649, No Frame #s.

(55.) Reichsluftfahrtministerium, Leistelle der Funkaufklaerung, Zusammenstellung bisher aufgetretener Feindstoerungen an deutschen Boden-und Bord-FuMG, Geheime Kommandosache, 7 February 1945, T-177, Roll 20, Frames 3706102, 3706112 & 3706115.

(56.) Lt. Cave to Maj. Abrignani, 2677th Regiment, OSS, Memo, 18 December 1944, RG 226, Entry 190, Box 96, Folder 91.

(57.) Numbers of captured personnel in Holland and France can be found in Giskes, London Calling North Pole, 122; McCue, SAS Operation Bulbasket, 215-16; and West, Secret War: The Story of SOE, Britain's Wartime Sabotage Organization, 126-30.

Chris Burton spent two years at the US. National Archives before joining the Center for Naval Analyses in 1981 as an Information Security Analyst. After CNA's reorganization as The CNA Corporation, a nonprofit research and analyses organization, he became its current Security Manager. He has written essays for information security newsletters and has contributed to the journal Military Review. He holds a bachelor's degree from Northern Arizona University and a master's degree from the University of Maryland, both in Modern European History. The opinions expressed in this article are those of the author.
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