The Oslo Report 1939—Nazi Secret Weapons Forfeited
By Frithjof A.S. Sterrenburg
Used by permission. All rights reserved

   The “Oslo Report” was perhaps the most serious breach of German security in the Second World War. It contained a wealth of data on top-secret weapons then under development in Germany and reached British Intelligence in early November 1939. Although it has often been referred to in the literature, such references merely consist of excerpts and paraphrases. The original German text is presented here. The English translation then used by British intelligence experts has not survived, the translation presented here is an idealized but realistic version: it could theoretically have been made at that time by a British intelligence analyst fluent in German and conversant with a wide range of technical developments, but strictly conforms to the status of 1939. Any re-interpretation based on our a posteriori knowledge has been avoided.

   The predominant attitude in British intelligence circles during the war was to regard the Oslo Report as unreliable, or even as a German deception operation. To determine whether there were good reasons for this suspicion, the text is critically analysed both as regards its prima facie contents and for its reliability as compared to the data on German secret technological developments of that period we now possess. Finally, its theoretical maximum impact (“what might have happened if the Oslo Report had been accepted as truth and countermeasures had been taken immediately?”) is compared to the actual situation as the war continued.

   The following conclusions are reached:

1) The Oslo Report was seriously unbalanced: the technical data are of very high quality, but items of a general military nature are useless or even ridiculous. Those British intelligence specialists who rejected the Oslo Report could present good arguments for doing so. This has never been paid due consideration in the literature.

2) Nevertheless it is shown that the Oslo Report contains information that categorically excludes a German deception operation, also in light of the knowledge of that time. Again, this has not been adequately considered in the literature.

3) The excerpts and paraphrases presented in the literature have been highly selective: they cover the arguments “pro” but disregard the arguments “contra." This is particularly the case for the principal author, R.V. Jones, who was closely involved with the evaluation of the Oslo Report during the war.

4) Even this catastrophic leak of information would not have yielded major military benefits to the British if it had been fully accepted and acted on from the beginning.

Seven Pages of Wisdom?

   On November, 5th, 1939, a parcel was delivered (ref. 1) to the British Embassy in Oslo, Norway—then still a non-belligerent country. A few days earlier, the Naval Attaché at the embassy, Hector Boyes, had found a letter in his mailbox asking whether the British would like to receive information on technical research and development then going on in Nazi Germany. If so, the usual announcement of the German news broadcasts by the BBC World Service should be changed to “Hullo, hier ist London”. Perhaps with some reluctance, the BBC complied with the request and this code message resulted in the delivery of the parcel. The package contained a kind of vacuum tube said to be intended to serve as a sensor in a proximity fuze for shells or bombs. The typewritten document accompanying it would become famous after its existence was revealed in 1947 and would go down in history as the “Oslo Report."

   The Oslo Report  has been mentioned in several books (e.g., ref. 1, 2, 3) dealing with secret weapons development in World War Two, with reference to some items of information it contained. R.V. Jones summarizes some of the Oslo Report’s contents (ref. 1) but references in other publications are just meagre one-liners. Are these copycat references? Was this the entire scope of the Oslo Report, which, after all, has been described as “some seven pages of typewritten text” (ref.1)?

   All the quotes in the literature were in English, so that it was impossible to determine whether the “overtones” of the original German text—which could well be of major importance—survived the translation process. A translation was made in 1939, by a member of the staff of the British Embassy in Oslo (ref. 4) and forwarded to British Intelligence together with the German text. This translator was not an experienced intelligence analyst additionally endowed with a wide-ranging scientific expertise plus fluency in technical German—a most unlikely triple combination of assets at that time. Because the subject was “secret weapons”,  he or she was faced with totally new devices and perhaps new German terminology. Under these circumstances, the fine nuances of the German text could easily have been missed. 

   An example of such nuances is to be found in the case of the V-1, the first cruise-missile, variously called the  “flying bomb”, “buzz bomb” or “doodlebug” by its recipients. One of its official designations was FZG-76, an abbreviation of “Flak Zielgerät 76”. Churchill's influential adviser Professor F.A. Lindemann spoke some German and as the German verb “zielen” means “to aim”, he concluded (ref. 5)  that the FZG-76 was an anti-aircraft aiming device—possibly a new predictor set for fire control, but anyway of only minor relevance. However, the German noun “Ziel” means “target” and thus translated the Flakzielgerät would become a target drone, an application that would indeed have fitted a V-1 minus its warhead. According to the standard German military vocabulary of that time, an anti-aircraft predictor set would have been called a Flak Kommandogerät. 

   The Imperial War Museum, London, posseses a 7-page carbon copy of this report in its archives, together with an English translation. Both of these documents were transferred to the IWM from the Cabinet Office Historical Section in the late 1980s. It seems that the German text was typed up in 1939 by the British Naval Attaché’s office in Oslo from an original now lost—at least according to a note which accompanied it when it reached the IWM. 

   Some details have been lost in the mists of time, but a reconstruction of the main aspects is as follows. The author of the Oslo Report was later identified (ref. 6) as Dr. Hans Ferdinand Mayer, the director of the Central Laboratory of Siemens & Halske, one of the major German “hi-tech” enterprises. Upon receipt of the package, a translation was made in the British Embassy in Oslo and in the pre-photocopier era, the German document was retyped, with a number of carbon copies being made for distribution to the authorities in Great Britain. A specimen of the original translation has not been located; the German text kept in the IWM is one of the carbon copies and lacks the sketches that apparently accompanied the original. The inclusion of these sketches in the report was notably omitted in Jones’ work (ref. 1), nor has it been mentioned in the subsequent literature, to my knowledge.

   It is not known how the original came to be lost, but when Norway was invaded by the German forces on April 9th, 1940, the Oslo Report obviously did not fall into German hands, because this would have led to such a frantic German security operation that some trace would have survived in the records. 
In the following pages, I shall first reproduce the full German text of the carbon copy. The English translation I then present is my own, in which I have scrupulously avoided the use of any retrospective knowledge. In other words, I have looked at the German text with the eyes of an hypothetical British intelligence analyst fluent in German and endowed with scientific and technical expertise—but strictly limited to 1939 status. In my view, this English translation represents the best result that could have been expected at the time whilst avoiding re-interpretation based on historical hindsight. I have not exploited the Todhunter translation in the IWM for my own text, because it was obviously a later version for the Cabinet Office Historical Section. 

   The Oslo Report reached British Intelligence as a bolt out of the blue, at a time when nobody had an inkling of what was yet in store. As is evident (ref. 4), the information was not received with acclaim, but rather with indifference or even denigration. One notable exception was Dr. R.V. Jones, a young scientist who had just been put in charge of a new field called “Scientific Intelligence”. Why Seven Pages of Wisdom could have been regarded as a diabolical “plant” by British Intelligence  analysts is a question calling for an answer. To find arguments both in favour of, and against, its credibility in 1939, I shall present a critical analysis of the information contained in the Oslo Report, comparing it with the actual (1939) state of development of the secret weapons mentioned. This will also be a check of the veracity and accuracy of the document. Finally, I shall try to draw conclusions on the potential and the actual impact of the Oslo Report.

The Text

   Original German text

   This is an exact transcript of the German text that has survived in the IWM. Notes (mine) in italics indicate typos in the German typewritten text. The surviving copy uses “ss” instead of the usual German “ß”, most probably because the typewriter available in the British Embassy did not have the latter sign.


1) Ju 88 Programm. Ju 88 ist ein zweimotoriger Langstreckenbomber und hat den Vorteil dass er auch als Sturzbomber verwendet werden kann. Es werden im Monat mehrere Tausend, wahrscheinlich 5000, hergestellt. Bis April 40 sollen 25 - 30 000 Bomber allein von dieser Sorte fertiggestellt sein. 

2) Franken. Im Hafen von Kiel liegt das erste deutsche Flugzeugmutterschiff. Es soll bis April 40 fertiggestellt sein und heisst "Franken".

3) Ferngesteuerte Gleiter. Die Kriegsmarine entwickelt ferngesteuerte Gleiter, d.s. kleine Flugzeuge von etwa 3 m Spannweite und 3 m Länge die eine grosse Sprengladung tragen. Sie haben keinen motorischen Antrieb und werden von einem Flugzeug aus grosser Höhe abgeworfen. Sie enthalten:

-    Einen elektrischen Höhenmesser, ähnlich des radio altimeter (Bell Syst. Tech. J. Jan. 39, p. 222). Dieser bewirkt dass der Gleiter in etwa 3 m über dem Wasser abgedangen (typo for abgefangen) wird. Er fliegt dann horizontal mit Raketenantrieb weiter.

 -   Eine Fernsteuerung mittels UKW-Wellen in Form von Telegraphiesignalen, durch die der Glieder (typo for Gleiter) nach rechts oder nach links oder grade aus gesteuert werden kann, z.B. von einem Schiff oder einem Flugzeug aus.

Der Gleiter soll so gegen die Bordwand eines feindlichen Schiffs gelenkt werden und dort soll die Sprengladung abfallen und unter Wasser explodieren.

Die Geheimnummer ist FZ21 "Ferngesteuerte (typo for ferngesteuertes) Zielflugzeug". Die Erprobungsstelle ist in Peenemünde, an der Mündung der Peene, bei Wolgest (typo for Wolgast) in der Nähe von Greifswald.

4) Autopilot. Unter der Geheimnummer FZ10 wird in Diepensee bei Berlin ein Autopilot entwickelt (Ferngest. Flugzeug) das von einem bemannten Flugzeug aus gesteuert werden soll um z.B. Ballonsperren zu zerstören.

5) Ferngesteuerte Geschosse. Das Heereswaffenamt (HWA) ist die Entwicklungsstelle für das Heer. Diese Stelle befasst sich mit der Entwicklung von Geschossen von 80 cm. Kaliber. Es wird hierbei ein Raketenantrieb verwendet, die Stabilisierung erfolgt durch eingebaute Kreisel. Die Schwierigkeiten beim Raketenantrieb liegen darin, dass das Geschoss nicht gradeaus fliegt sondern unkontrollierbare Kurven macht. Es hat daher eine drahtlose Fernsteuerung, mit der der Abbrand des Zündsatzes der Rakete gesteuert wird. Diese Entwicklung ist noch in den Anfängen und die 80 cm Geschosse sollen später für die Maginotlinie eingesetzt werden.

6) Rechlin. Dieses ist ein kleiner Ort am Mueritzsee, nördlich Berlin. Dort befinden sich die Laboratorien und Entwicklungsstellen der Luftwaffe, lohnender Angriffspunkt für Bomber.

7) Angriffsmethode für Bunker. Die Erfahrungen im Feldzug gegen Polen haben gezeigt, dass mit einem gewöhnlichen direkten Angriff gegen Bunker nicht angekommen (Note: “werden” is missing here)  kann. Die polnische Bunkerstellungen wurden daher durch Gasgranaten vollkommen eingenebelt, wobei die Verneblung wie ein Vorhang immer tiefer in die Bunkerstellungen vorgetragen wurde. Die polnische Mannschaften wurden so gezwungen, sich in die Bunker zurückzuziehen. Unmittelbar hinter der Verneblungswand rückten deutsche Flammenwerfer vor und nahmen vor den Bunkern Aufstellung. Gegen diese Flammenwerfer erwiesen sich die Bunker als machtlos und die Bunkerbesatzung kam entweder um oder musste sich ergeben. 

8) Fliegerwarngerät. Bei dem Angriff der englischen Flieger auf Wilhelmshafen Anfang September wurden die englischen Flugzeuge schon 120 Km vor der deutschen Küste festgestellt. An der ganzen deutschen Küste stehen Kurzwellensender mit 20 KW Leistung, die ganz kurze Impulse, von der Dauer 10-5 sec. aussenden. Diese Impulse werden von den Flugzeugen reflektiert. In der Nähe des Senders ist ein drahtloser Empfänger, der auf die gleiche Welle abgestimmt ist. Dort trifft also nach einiger Zeit die vom Flugzeug reflektierte Welle ein und wird von einem Braunschen Rohr registriert. Aus dem Abstand des Sendeimpulses und des reflektierten Impulses kann man die Entfernung des Flugzeuges ersehen. Da der Sendeimpuls viel stärker ist als der reflektierte Impuls wird der Empfänger während des Sendeimpulses gesperrt. Der Sendeimpuls wird auf dem Braunschen Rohr durch ein örtliches Zeichen markiert. In Verbindung mit dem Ju 88 Programm werden überall in Deutschland bis zum April 40 
solche Sender installiert.

Gegenmassnahmen. Mittels besonderer Empfänger, die Impulse von der Dauer 10-5  - 10-6 sec. aufnehmen können, muss man die Wellenlänge der in Deutschland gesendeten Impulse feststellen und dann auf den gleichen Wellenlängen Störimpulse aussenden. Diese Empfänger können an Land stehen, auch die Sender, da die Methode sehr empfindlich ist.

Während diese Methode in grossem Umfang eingeführt wird, ist ein anderes Verfahren in Vorbereitung, welches mit 50 cm Wellen arbeitet. Siehe Fig. 1. Der Transmitter (Note: German text uses English here) T sendet kurze Impulse aus die mit einem elektrischen Hohlspiegel stark gerichtet sind. Der Receiver (Note: German text uses English here) R steht unmittelbar neben dem Sender und hat ebenfalls eine Richtantenne. Er empfängt die reflektierten Impulse. T und R sind über eine künstliche Leitung miteinander verbunden, deren Uebertragungszeit stetig veränderlich ist.

Diese künstliche Leitung hat folgenden Zweck: der Empfänger ist für gewöhnlich gesperrt und kann keine Impulse empfangen. Der Impuls, der von T drahlos ausgesendet wird, läuft auch über die künstliche Leitung und macht den Empfänger für eine ganz kurze Zeit wirksam. Wenn die Uebertragungszeit der künstlichen Leitung  gleich ist der Laufzeit des reflektierten drahtlosen Impulses, kann dieser vom Empfänger auf einem Braunschen Rohr registriert werden. Mann kann mit diesem Verfahren sehr genau die Entfernung z.B. eines Flugzeuges messen und es ist sehr unempfindlich gegen Störungen, da der Empfänger immer nur sehr kurze Zeit geöffnet ist.

9) Flieger-Entfernungsmessgerät. Wann Flieger zum Angriff in ein feindliches Land fliegen, ist es wichtig für sie zu wissen, wie weit sie vom Ausgangsort entfernt sind. Für diesen Zweck wird in Rechlin folgendes Verfahren entwickelt:

Am Ausgangsort steht ein drahtloser Sender (6 m. Welle), der mit einer Niederfrequenz f moduliert ist.Das Flugzeug, das in der Entfernung a ist, empfängt die 6 m Welle und erhält nach der Demodulation die Niederfrequenz f. Mit dieser Niederfrequenz moduliert es seinen eigenen Sender, der eine etwas andere Wellenlänge hat. Die so modulierte Welle des Flugzeugs wird am Ausgangsort empfangen und demoduliert. Die so erhaltene Niederfrequenz f. wird mit der örtlichen Niederfrequenz f. verglichen. Beide unterscheiden sich durch den Phasewinkel  4?fa/C (a= Entfernung des Flugzeugs, C = Lichtgeschwindigkeit). Durch Messung der Phase kann man also die Entfernung des Flugzeugs messen und man kann dem Flugzeug seinen Standort mitteilen. Damit die Messung eindeutig ist muss der Phasenwinkel unter 2? bleiben. Man wählt daher eine niedrige Freq. f, z.B. 150 pps, dann ist gerade für 1000 Km der Phasewinkel gleich 2?. Mit einer so tiefen Frequenz erhält man jedoch keine sehr grosse Genauigkeit. Man sendet daher gleichzeitig eine zweite, höhere Frequenz aus, z.B. 1500 pps und vergleicht auch hiervon den Phasewinkel. 150 pps also eine Grobmessung, 1500 pps eine Feinmessung.

10) Torpedos.  Die deutsche Marine hat 2 neue Arten von Torpedos:

a) Man will z.B. Convoys von 10 Km Entfernung aus angreifen. Solche Torpedos haben einen drahtlosen Empfänger, der 3 Signale empfangen kann. Mit diesen Signalen kann man von dem Schiff, welches das Torpedo geschossen hat, oder von einem Flugzeug aus, das Torpedo nach links, nach rechts oder gradeaus steuern. Es werden lange Wellen verwendet, die gut in das Wasser eindringen, in der Ordnung von 3 Km-Wellen. Diese sind mit kurzen Tonfrequenzsignalen moduliert welche die Steuerung des Torpedos veranlassen. Auf dieser Weise soll das Torpedo in grosse Nähe des Convoy gelenkt werden. Um nun ein Schiff wirklich zu treffen sind am Kopf des Torpedos 2 akustische Empfänger (Mikrofone) welche einen Richtempfänger darstellen. Mit diesem Empfänger wird der Lauf des Torpedos so gesteuert, dass es von selbst auf die akustische Geräuschquelle läuft. Wenn also das Torpedo drahtlos in eine Entfernung von wenigen 100 m von dem Schiff gebracht worden ist, läuft es von selbst auf das Schiff los, da jedes Schiff wegen seiner Maschinen akustische Geräusche macht. Mit akustischen und drahtlosen Störsignalen kann man sich verhältnissmässig leicht dagegen schützen.

b) Die zweite Art von Torpedo ist wahrscheinlich diejenige, mit der die Royal Oak versenkt wurde. Diese treffen nicht die Schiffswand sondern explodieren unter dem Schiffsboden. Die Auslösung der Zündung erfolgt magnetisch und beruht auf folgendem Prinzip: Fig. 2. Die Vertikalkomponente des magnetischen Erdfelds ist überall ungefähr dieselbe, wird aber durch das Schiff S verändert, sodass bei A und C ein schwächeres Feld, bei C ein stärkeres Feld ist. Ein von Links kommendes Torpedo läuft also erst im normalen Feld, dann im schwächeren Feld usw.

Im Kopf des Torpedo rotiert nach Art eines Erdinduktors eine Spule um eine horizontale Achse. An den Klemmen dieser Spule entsteht hierdurch eine Gleichspannung, die der Vertikalkomponente des magn. Erdfelds proportional ist. In Reihe mit dieser Spannung lieft (Note: error for” läuft”) eine gleichgrosse Gegenspannung, so dass kein Strom fliessen kann, solange das Torpedo sich in normalen Erdfeld befindet. Kommt jedoch das Torpedo nach A, so ist dort das Erdfeld  kleiner und die Spannung an der rotierenden Spule sinkt. Die beiden entgegengesetzten Spannungen sind nicht mehr gleich gross, es fliesst ein Strom und betätigt ein Relais welches die Zündung auslöst. Die Verzögerung ist so gewählt, dass die Explosion grade unter den Schiffsboden erfolgt.

Vielleicht kann man sich gegen solche Torpedos schützen, indem man längs des Schiffes ein Kabel ausspannt, etwa in Höhe des Schiffsboden und möglichst weit von der Schiffswand entfernt. Wenn man durch dieses Kabel einen passend gewählten Gleichstrom schickt, kann man ebenfalls ein magnetisches Feld erzeugen und den gefährlichen Punkt A weit ausserhalb des Schiffs verlegen. Das Torpedo wird dann zu früh explodieren. Vielleicht ist es auch möglich durch passend gewählte Kompensationsspulen die Verzerrung des magnetische Erdfeld durch die Riesenmassen des Schiffs zu kompensieren.



In Deutschland geht man von den mechanischen Zuendern ab und will dafür elektrische Zuender verwenden. Alle Z. für Fliegerbomben sind schon elektrisch. Fig. 1 zeigt das Prinzip. Wenn die Bombe das Flugzeug verlässt wird ueber einen Gleitkontakt der Kondensator C1 aus einer Batterie mit 150 Volt aufgeladen. Dieser laedt über den Widerstand R den Kondensator C2 auf. C2 ist erst geladen wenn die Bombe in einer ungefährlichen Entfernung vom Flugzeug ist. Wenn die Bombe auftrifft, schliesst sich ein mechanischer Kontakt K und der Kondensator entlaedt sich über die Zündspule Z. Der Vorteil ist, dass die Bombe niemals scharf sein kann, wenn sie am Flugzeug haengt; man kann daher mit Bomben ungefaehrlich landen.

Fig. 2 zeigt einen elektrischen Zeitzuender. Es ist das gleiche Prinzip, nur ist an Stelle des mechanischen Kontakts eine Glimmlampe G., welche nach einer ganz bestimmten Zeit zuendet. Diese Zeit kann durch die Werte der Kondensatoren und Widerstaende eingestellt werden.

Die neueste Entwicklung verwendet Glimmlampen mit Gitter, Fig. 3. Wenn man die Batteriespannung so waehlt, dass sie etwas unterhalb der Zuendspannung liegt und wenn das Gitter isoliert ist, kann man durch Veraenderung der Teilkapazitaeten C12 und C23 die Lampe zur Zuendung bringen. Es genuegen schon ausserordentlich kleine Veraenderung (Note: typo for “Veraenderungen”) der Teilkapazitaeten. Fig. 4 zeigt den prinzipiellen Einbau in einem Geschoss. Der Kopf K des Geschosses ist isoliert und liegt am Gitter der Glimmlampe. Fliegt das Geschoss z.B. an einem Flugzeug vorbei, so werden die Teilkapazitaeten etwas veraendert, und die Lampe zuendet wodurch das Geschoss explodiert. Man kann den Zuender auch so einstellen dass alle Geschosse in einem ganz bestimmten Abstand ueber dem Erdboden, z.B. in drei Meter Höhe explodieren. 

Eine solche Lampe mit Gitter lege ich bei, es gibt eine verbesserte Lampe bei der das Gitter aus einem Ring besteht. 

Der Abwurf-Zuender für Bomben hat die Bezeichnung Nr. 25, die Fertigung soll von 25,000 Stueck in Oktober 1939 auf 100,000 Stueck ab April 1940 gesteigert werden.

Diese Zuender werden in Sömmerda in Thuringen an der Eisenbahn Sangershausen-Erfurt hergestellt. Die Firma heisst Rheinmetall. 


   English Translation

   This translation is strictly based on the knowledge available in 1939. I have added notes (italics) where the hypothetical 1939 translator might have done so.

1) The Ju 88 Programme. The Ju 88 is a twin-engined long-range bomber and has the advantage that it can also be used as a dive-bomber. Several thousand, probably 5000, are being produced monthly. By April 1940,  25 – 30 000 bombers of this type alone are intended to have been produced.

2) Franken. The first German aircraft carrier lies in Kiel harbour. It is to be completed by April 40 and is named “Franken”.

3) Remote-controlled gliders. The Kriegsmarine is developing remote-controlled gliders, i.e. small aircraft of about 3 metres’ wingspan and 3 metres long, which carry a large explosive charge. They have no engine and are dropped by an aircraft from a great height. They contain: add dashes:

- an electric altimeter, similar to the radio altimeter (Bell Syst. Tech. J. Jan. '39, p. 222). This causes the glider to pull out when at about 3 metres above the water. Then it continues to fly horizontally with rocket propulsion.

- remote control by ultra-short waves in the form of telegraphy signals by which the glider can be steered to the right, to the left or straight ahead, e.g. from a ship or an aircraft. In this manner, the glider is to be aimed at the side of an enemy ship, at which point the explosive charge is to be dropped, to explode under water.

The code number is FZ 21 (remote-controlled target aircraft). The test site is at Peenemünde, at the mouth of the Peene, near Wolgast in the vicinity of Greifswald.

4)  Autopilot. Under the code number FZ10 an Autopilot (remote-controlled aircraft) is being developed in Diepensee near Berlin, which is to be controlled from a manned aircraft to destroy, for instance, balloon barrages.

5) Remote-controlled missiles (Note: or projectiles). The Heereswaffenamt (HWA) is the development centre for the Army. This centre is developing missiles (Note: or projectiles) of 80 cm calibre. Rocket propulsion is used; stabilization is by means of built-in gyros. The problem with rocket propulsion is that the missile does not fly in a straight line but in uncontrollable curves. Therefore it has radio remote control by which the “burn-off” (see note below) of the combustion unit can be steered. This development is only in the initial stages and the 80 cm missiles are intended to be used later against the Maginot Line. 

(Translator’s note: “Abbrand” is an ambiguous term. Literally meaning “burn-off”, it is used for  residues in iron production. It could mean “combustion products” here. For internal combustion engines the word “Abgas” is used for the exhaust gases and “Abbrand” might be used here in an analogous sense for a rocket.)

6) Rechlin. This is a small place on Lake Mueritz, north of Berlin. Here are situated the laboratories and development centres of the Luftwaffe, a rewarding target for bombers.

7) Method of attacking fortifications. Experience in the Polish campaign has shown that an ordinary direct attack is useless against fortifications. The Polish fortifications were therefore completely covered with smoke by gas grenades, the smoke being shifted ever deeper into the emplacements. The Polish troops were thus forced to withdraw into the emplacements. Immediately behind the smoke-screen, German flame-throwers came forward and took up positions in front of the emplacements. Against these flame-throwers the emplacements were powerless and their crews either died or surrendered.

8) Air-raid warning equipment. At the time of the attack by English airmen on Wilhelmshafen in early September, the English aircraft were already detected when they were still 120 Kms off the German coast. Along the entire German coast 20 kW short-wave transmitters have been installed, which transmit very short pulses of 10 –5 second duration. These pulses are reflected by the aircraft. Close to the transmitter a radio receiver is tuned to the same wavelength. After a certain interval, the pulse reflected by the aircraft arrives at the receiver and is displayed on a cathode-ray tube. From the interval between the transmitted and the reflected pulses the distance of the aircraft can be calculated. As the transmitted pulse is much stronger than the reflected pulse, the receiver is blocked during transmission. The transmitted pulse is displayed on the cathode-ray tube as a fixed mark.

In connection with the Ju-88 programme such transmitters are to be installed throughout Germany by April ’40. 

Countermeasures. With special receivers capable of registering pulses of 2 x superscript! 10 –5 to 10 –6 seconds, the wavelength of the pulses transmitted in Germany should be determined and interfering pulses should be transmitted on the same wavelengths. These receivers can be installed on the ground and the same applies to the transmitters, because the method is very sensitive.

While this method is being introduced on a large scale, another method is in the preparatory stage, which uses 50 cM waves, see Fig. 1. The transmitter T broadcasts short pulses, which are sharply focused with a concave electric reflector. The receiver R stands immediately next to the transmitter and likewise has a directional antenna. It receives the reflected pulses. T and R are connected by an artificial conductor (Translator’s note: transmission line) whose propagation time is continuously variable. This artificial conductor has the following purpose. Normally the receiver is blocked and cannot receive pulses. The radio pulse emitted by T also passes through the artificial conductor and activates the receiver for a very short time. When the propagation time through the artificial conductor equals the time interval before the reflected pulse arrives, the latter can be displayed on the receiver’s cathode-ray tube. With this method, the distance of an aircraft, for example, can be measured very precisely and the method is very insensitive to interference because the receiver is only open for a very short time.

9) Aircraft distance-measuring equipment. When airmen carry out an attack on a foreign country, it is important for them to know how far they are from their starting-point. For this purpose, the following procedure is being developed at Rechlin:

At the starting-point there is a radio transmitter (6 m band) modulated with an audio frequency f. The aircraft, at a distance a, receives the 6m wave and demodulation yields the audio frequency f. This audio frequency is used to modulate the aircraft’s own transmitter, which is tuned to a slightly different wavelength. This modulated signal emitted by the aircraft is received at the starting-point and demodulated. The resulting audio frequency f is compared with the local audio frequency. These two differ in the phase angle 4ttf. a / C, where: A = distance of the aircraft; C = speed of light.

By measuring the phase angle, one can therefore determine the distance to  the aircraft and can inform the aircraft of its position. For the measurement to be unambiguous, the phase angle must be less than 2tt. One therefore chooses a low frequency, e.g. 150 cps, so that for 1000 kms the phase angle is exactly 2tt.  With such a low frequency, no great precision can be attained, however. Therefore a second, higher (e.g. 1500 cps) frequency is transmitted simultaneously and its phase angle is also compared. So 150 cps for coarse, 1500 cps for fine measurement.

10) Torpedoes. The German Navy has two new types of torpedo:

a) For instance, it is desired to attack convoys from 10 kms distance. Such torpedoes have a radio receiver that can receive 3 signals. With these signals the torpedo can be steered to the left, to the right or straight ahead from the ship that has launched the torpedo or from an aircraft. Long waves are used, which penetrate well under water, of the order of 3 kms. These are modulated by short audio frequency signals which steer the torpedo. In this manner the torpedo is to be guided to within the vicinity of the convoy. To actually hit a ship, the head of the torpedo contains two acoustic receivers (microphones), which constitute a directional receiver. With this receiver the course of the torpedo is so adjusted that it automatically runs towards the source of the acoustic noise. When the torpedo has been steered by radio to within a few hundred metres of the ship, it automatically runs towards that ship as any vessel will make acoustic noise because of its engines. With acoustic and radio interference, it is relatively easy to protect oneself.

b) The second type of torpedo is probably the one that sank the Royal Oak. These do not hit the ship’s hull but explode underneath the ship’s bottom. The detonation is initiated magnetically and is based on the following principle: Fig. 2.

The vertical component of the terrestrial magnetic field is approximately the same everywhere, but it is altered by the ship S so that it is weaker at A and C and stronger at C (Translator’s note: error for B?). A torpedo coming from the left first runs in a normal field, then in a weaker one etc.

The head of the torpedo contains a coil rotating about a horizontal axis in the manner of an earth inductor. At the terminals of this coil, a DC voltage is developed, proportional to the vertical component of the terrestrial magnetic field. In series with this voltage a voltage of equal amplitude but opposite polarity is supplied so that no current can flow while the torpedo runs in the normal terrestrial field. When the torpedo arrives at A, however, the magnetic field is smaller and the voltage developed at the rotating coil terminals decreases. The two opposite voltages are no longer equal, current flows and activates a relay, triggering the fuze. A delay has been chosen such that the explosion takes place exactly underneath the ship’s bottom.

Perhaps one can protect oneself against such torpedoes by running a cable along the ship, at about the level of the ship’s bottom and as far away from the hull as possible. When a suitable direct current is passed through this cable, this also creates a magnetic field and the critical point A will be shifted to a position far away from the ship. The torpedo will then explode prematurely. Perhaps it is also possible to compensate for the distortion of the magnetic field caused by the great mass of the ship by means of suitably selected compensation coils.



In Germany, mechanical fuzes are being discontinued and the intention is to use electric fuzes instead. All fuzes for bombs are already electrical. Fig. 1 shows the principle. When the bomb leaves the aircraft, the condenser C1 is charged by a 150 V battery via a sliding contact. This charges the condenser C2 via a resistor R. C2 only becomes charged when the bomb is at a safe distance from the aircraft. When the bomb hits, a mechanical contact K closes and the condenser discharges over the ignition coil Z. The advantage is that the bomb can never be “live” when it is still attached to the aircraft, which can thus be landed safely with the bombs still on board. 

Fig. 2 illustrates an electrical time-fuze. This uses the same principle, only instead of the mechanical contact there is a neon lamp G, which ignites after a precisely determined interval. This interval can be preset by the values of the condensers and resistances. 

The newest development uses neon lamps with grids, Fig. 3. When the battery voltage is so chosen that it is just below the ignition voltage and when the grid is insulated, the lamp can be ignited by changes in the partial capacitances C12 and C23. Extremely small changes in the partial capacitances are already sufficient. Fig. 4 shows the principle of incorporation in a projectile. The head of the projectile K is insulated and connected to the grid of the neon lamp. When the projectile passes near an aircraft, for example, the partial capacitances are slightly altered and the neon lamp ignites so that the projectile explodes. Also, the fuze can be so adjusted that all projectiles explode at a precisely determined height above the ground, e.g. at three metres. 

Herewith I enclose such a lamp with grid; there is an improved lamp in which the grid consists of a ring.

The bomb-release fuze bears the number Nr. 25; production is to be increased from 25,000 in October 1939 to 100,000 as from April 1940.

These fuzes are manufactured in Sömmerda, Thüringen, along the railway from Sangershausen to Erfurt. The firm is called Rheinmetall. 


Trick or Treat?

   From R.V. Jones’s writings (ref. 1), we know that while he took the Oslo Report seriously, several British intelligence experts regarded it as a “plant”—a red herring aimed at deception and confusion of the enemy, cloaked in pseudo-veracity by supplying some information that is indeed correct. Retrospectively, one might tend to disparage the expertise of these doubters, but one should consider the Oslo Report in the light of 1939 and not with our perfect historical hindsight. I will try to make a fair case for both the believers and the doubters by critically examining the Oslo Report’s information purely from the 1939 technical perspective and then combine this with a posteriori comments.

   Of necessity, an intelligence “plant” has to give away information that is new to the enemy, in order to raise his interest. This information must not be too difficult for the enemy to verify, and when he does so, it must be confirmed as correct—so as to establish trust. On the other hand, the information one gives away to his enemy may not seriously damage one’s own military interests. A plant will, therefore, have a certain hollow ring to it—the secrets it reveals that are indeed found to be true will be rather bland.

  1).  The Ju-88 programme:

   Unfortunately, the above characteristics of a “plant” are a perfect description of the Oslo Report information on the Ju-88 bomber, for the following reasons. The Ju-88 had been widely publicized by the Germans before the war as the “Wonder Bomber” and thanks to the official records it had established, its high performance was well known. The Ju-88, for that time a large and heavy twin-engined machine, had originally been conceived as an unarmed bomber too fast for fighters to catch—exactly the same concept as the later British de Havilland Mosquito. Where the Mosquito brilliantly succeeded, the Ju-88 failed, however. The addition of armament that was subsequently deemed necessary and the strengthening required when dive-bombing had to be added to its repertoire (as per decree of the Luftwaffe leadership) compromised its initially sparkling performance.

   What would the information on the Ju-88’s dive-bombing capability have meant to a British analyst in 1939? If such an aircraft was to operate as a dive-bomber, the Germans were apparently able to build strong aircraft—but given the reputation of German engineering that could hardly have been in doubt anyway. But the mere mention of “dive-bombing” would have tended to douse the interest of a British analyst nurtured in the catechism of the RAF, for the concept of dive-bombing went against the RAF’s very psychological grain. Pin-point accuracy bombing reeked of a subordinate role of aviation in direct support of the army, and the raison d’être of the RAF was as an independent force on an equal hierarchical footing with the Royal Navy and the British Army. Hence, dive bombing was regarded as anathema in the RAF, so much so that the use of the word itself had been forbidden. Since 1938, it had been decreed (ref. 7) that the only acceptable expression was “losing height bombing”! The psychological make-up (and concern about their career prospects!) of RAF analysts would thus tend to make them regard any reference to this “confounded losing height bombing” as irrelevant.

   The blandness characteristic of an intelligence plant is also illustrated in this Ju-88 item. The “secret” of its dive-bombing capability would immediately be lost in the first such attack. In fact, the secret was out already when the Oslo Report was written, because the Ju-88 had been used on operations against the British by then (ref. 8). Taken together, these considerations can be regarded to make a perfect case for the doubters: from the 1939 perspective they might well conclude that this was a true but unimportant pseudo-secret given away to establish a false sense of trust.

   The additional information supplied in the Ju-88 item makes the case for the doubters even stronger: production targets of the Ju-88 are said to amount to several thousand, probably 5000, a month at the time of writing. There are many examples in military intelligence where the capabilities of the enemy are ridiculously underestimated (the official American doctrine in 1941 was that Japanese pilots were very poor as they were handicapped by defective eyesight) or wildly overestimated (large-scale evacuation of London was carried out in 1939 as the casualties of German bombing were predicted to run into six figures). But surely anyone in Great Britain in 1939 even vaguely familiar with aircraft production would have rejected this production estimate even in his most pessimistic mood. And as we now know that the author of the Oslo Report had a high position in German industry, we can only assume that he himself was lured by the Nazi propaganda.

   For a production target of 5000 Ju-88’s a month, the sheer requirements in light alloys would have been prohibitive. Also, it would require 5000 multi-unit FuG10 radio sets and 10,000 Jumo 211 engines a month, to name but two important components, and all this for just one type of aircraft in the armoury. But above all, it would require a gigantic Luftwaffe training-capacity. If we assume that some of the production is to compensate for wear and tear, the force still should have to be built up by something like >3000 crews a month. With a four-man Ju-88 crew, this would require >12,000 fully trained new crew members a month. As many pupils will fail the course and training will take many months for the key crew members such as pilots and the important German Beobachter (observers, generally speaking highly experienced pilots), the intake of candidate crew members for the Ju-88 alone should have reached a figure of something like 20,000 a month starting in 1938 at the latest. This is pure hallucination: in 1938 the streets of Germany would have been awash with Luftwaffe cadet uniforms, the skies would have been a solid mass of trainers. For a sober 1939 British intelligence analyst, the claim that 5000 Ju-88’s were produced monthly would be unacceptable.

   With hindsight, we know that in reality, the Ju-88 situation was bleak in 1939. The addition of the dive-bombing requirement, combined with the problems normally attendant to the introduction of any new item of ordnance, had resulted in serious delays. In fact, in the autumn of 1939 the Ju-88’s available to the Luftwaffe numbered fewer than fifty. In the Ju-88’s first operation, an attack on ships of the Royal Navy in the North Sea on September 26th, 1939 by I/KG30, only 4 aircraft were used and these included some preproduction machines (ref. 9) and by April 9th, 1940 (Operation Weserübung, the invasion of Denmark and Norway), KG30 still had only a total strength of 84 Ju-88A’s. The total production of all subtypes of the Ju-88 between 1939 and 1945 amounted to circa 15,000 (ref. 10)!

  2.  “Franken” 

   The next item switches from the Luftwaffe to the Kriegsmarine, and might have sufficed to destroy any remaining British interest in the Oslo Report. A ship is formally named at launch, which for the first German aircraft carrier took place in December 1938. As war had not yet broken out at that date, the launch was surrounded by all the usual propaganda pomp and circumstance, covered extensively for the general public by the press and photographers. The hull of the carrier prominently displayed her name in giant lettering for all to see: GRAF ZEPPELIN. 

   In the German Empire, i.e. up to 1918, the individual contributions of the states forming the nation to its common armed forces were recognized by naming capital ships after them. Thus, there were battleships named “Schlesien”, “Pommern” and  “Bayern”, for instance. In the Second World War, the emphasis was on Germany as a monolithic political unit and the old feudal states (of which Franken is one) were downplayed. Thus, capital ships in Nazi Germany were named after great statesmen or military leaders— “Bismarck”, “Hipper” etc. In 1939 there was indeed a “Franken” in the Kriegsmarine, but this was a humble fishery steamer, which amazingly entered the history books by “arresting” the British submarine Seal and its crew on May 5th, 1940 (ref. 11). 

   Both from the 1939 perspective and with historical hindsight, it is unclear how the author of the Oslo Report came to supply this piece of spurious information. A new “Franken” supply ship was indeed under construction, on a slipway next to that of the Graf Zeppelin, but it could not be reasonably be confused with the aircraft carrier. For a 1939 intelligence analyst, this Franken tale would have appeared as a clumsy attempt at disinformation or a singularly ill-informed item for the trashbin. It is most unfortunate that the Oslo Report opens with two items that would definitely not pass scrutiny in 1939. First impressions being as important as they are, a British intelligence expert would justifiably have become at least extremely wary of the Oslo Report right from the beginning. 

  3)  Remote-controlled glider

   All of a sudden, we enter a totally different level of information, a technical description with detailed specifications. The modern reader may be surprised to find a clear outline here of what we now call a sea-skimming missile, such as the Exocet that became a byword in the 1982 Falkland conflict. Certainly in 1939 the weapon described appeared to be extremely advanced—but not entirely unrealistic, as many of the technical principles involved were common knowledge.

   Rocket propulsion had been discussed for a long time, and in the First World War aircraft had been armed with Le Prieur rockets for attacks on observation balloons and Zeppelins. In the late Twenties, much publicity had been generated by rocket-driven cars and gliders sponsored by the German car manufacturer Fritz von Opel. Finally, by 1939 several countries were working on somewhat more advanced rockets that eventually saw service as air-to-ground missiles, the bazooka, Katyusha and equivalents.

   Radio-controlled aircraft were well known too, as many experiments had been carried out in the Thirties. In Great Britain these had led to the production of an anti-aircraft target drone, the de Havilland Queen Bee. The radio-altimeter mentioned in the text had been described in the publicly available literature. The only question—though it is a vital one—is whether this would still work at an altitude as low as 3 metres. A puzzling point is that the missile is first stated to have no engine, and next said to be powered by a rocket engine; but this Oslo Report item could not be rejected out of hand in 1939.

   In fact, it is an almost exact specification of the Blohm & Voss BV-143. This had a span of about 3 metres, was released as a glider and for its final flight was powered by a rocket engine. It was indeed intended to be a sea-skimmer, its altitude to be controlled by a long streamlined probe in contact with the water surface. When this did not work, a radio altimeter was tried but development was not successful. Flying on instruments at extremely low altitude is a task very difficult to solve technically. The British encountered the problem for the attack on the Ruhr Dams in March, 1943 and solved it cheaply and elegantly with two intersecting spotlights, but that worked only by night, with a human observer in the loop and over a smooth water surface.

  This item is notable for its inclusion of Peenemünde, the first (and very early) reference to this top secret research centre available to British intelligence. One intrigueing item of information is that the warhead is supposed to drop on impact of the missile and explode under water. Certainly, an explosion under water is much more destructive than one in air but it is unrealistic to assume that a warhead could have survived the impact of a fast-moving missile, then to drop into the water and detonate. In fact, this was not  tried in the BV-143.

  4. Autopilot

   In view of the development of remote-controlled aircraft in the Thirties mentioned above, this item would also have been quite acceptable in 1939. We now know that many such projects were being tackled in Germany at that time but the description given is too general to relate it to any specific weapon. From the 1939 intelligence point of view, not much information could have been deduced from this item, but it cannot be rejected out of hand.

  5. Remote-controlled missiles

  I have made the hypothetical 1939 translator use the words “missile or projectile” here because although the German word Geschoss can also mean shell, the German text states that a rocket is involved, which is not fired from a gun. The latter is evident from the remark that the projectile is very unstable at the start, whereas a shell fired from the rifled guns of that time was spin-stabilized, or fin-stabilized in the case of mortar rounds.

   From the British perspective of 1939, this is a most curious item. Even in the summer of 1943 (ref. 12), British rocket engineers were focused on solid fuels such as cordite—improved fireworks, in fact. They would think in diameters of typically 3 inches and a solid fuel rocket of more than ten times this diameter would have caused a credibility gap—as it in fact did when more information on this presumed monster firecracker became available to British intelligence later on. The one crucial bit of information lacking here—and given the quality of the rest of this item it is surprising that the Oslo Report author did not mention it—is the use of liquid fuels, viz. methanol and liquid oxygen, in the German ballistic rocket programme. Liquid fuels had been tested also outside Germany in the inter-war years, by Goddard in the USA, for instance.

   With hindsight, this description is recognizable not as the A-4 (later called the V-2) but most probably as the A-5, a smaller interim model specifically intended to work out the control difficulties described in the Oslo Report. Thanks to TV, it’s now common knowledge that a large rocket lifts off very slowly and control surfaces on fins will thus be inoperative as there is insufficient airflow. The solution worked out by the German engineers, and one of the decisive elements in their revolutionary concept of the ballistic rocket, was the use of control surfaces for deflection of the rocket exhaust, now called thrust vectoring.

   This brings us to the word “Abbrand” used in the Oslo Report and the note I made the hypothetical 1939 translator write. Here is a fine example of the importance of linguistic overtones. At present “Abbrand” is used for a variety of concepts ranging from the fission process in nuclear reactors to co-combustion of biomass in coal-fired power plants, but its original (and still valid) meaning was related to the iron industry. I have tested this word in the Oslo Report context on several scientifically-educated native German speakers and they were puzzled, but all were content with an equivalent of “Abgas” when I suggested it. Perhaps I have made the hypothetical 1939 translator exceedingly clever, but from the context one now cannot but conclude that the Oslo Report author referred to such thrust vectoring. The V-2 did not normally incorporate radio control but such experiments were indeed carried out in its development programme (refs. 13, 14).

   Although this is one of the more important revelations, it would have been extraordinarily difficult in 1939 for British experts to fully grasp its importance—they were stuck with the firecracker idea and the Germans were simply already too far ahead for them to follow easily. 

   6. Rechlin 

   Rechlin was the German equivalent of Farnborough and like the latter was well-known in intelligence circles. This is therefore an insignificant piece of information—which again might be suggestive of an intelligence plant. The exhortation to bomb it is interesting, as the author is talking about his own people. 

   7. Attacking fortifications

   A military tactician of 1939 may well have frowned at this information. In the first place, the author confuses gas grenades and smoke grenades. In the second place, it is not evident why the troops outside the bunkers should be at a disadvantage when they go inside the bunkers—after all, these have the specific purpose of offering protection to troops. Nor is it clear why they should withdraw into the bunkers because of smoke, as their view would then be even more limited.

   This fortification item only makes sense if it is read as “cover the site in smoke so that observation by the enemy is made impossible and under this cover move flame-throwers right up to the slits”. That was not a military secret and therefore this item is a useless piece of information—in 1939 as well as in retrospect.

  8. Air raid warning apparatus

   As in the switch from item 2) to 3), we suddenly seem to select technical overdrive here. From the perspective of 1939, anyone with up-to-date knowledge of high-frequency radio (not just engineers but even advanced amateur radio experimenters of whom there was a large reservoir in the Radio Society of Great Britain, for instance) would sit up and notice.

   It would be immediately clear even in 1939 that this is a detailed description of what was then for security reasons known as RDF (radio direction finding) in Great Britain and as DT Gerät (decimeter telegraphy equipment) in Germany: a method of detecting targets by radio. Each and every principle outlined would be either known to a well-informed radio expert, or easily verifiable in the public literature. However, the combination of these principles in a lucid exposé, making this item almost a DIY “how to build a radar” primer, would have been regarded as an horrendous breach of security in any country then involved in radar development. Besides the principles, the actual implementation of such a radio detection system in Germany is revealed and its range capability (120 kms) is specified. Finally, progress in research on yet another radio detection system working at the then ultra-high frequencies around 50 cms (600 MHz) is mentioned. Such ultra-short wavelengths were known to be theoretically advantageous for this purpose because they make very sharp beams possible, but 600 MHz was at the very limit of what was then technically feasible.

   Little more than a month after the Oslo Report was received, Mr Bainbridge-Bell, a specialist from TRE (Telecommunications Research Establishment, a centre of British high-frequency research) climbed the wreck of the German pocket battleship Admiral Graf Spee in the Plata estuary, Argentina, and reported that the complex aerial system on its foremast was such a radio detection apparatus—a report whose subsequent neglect by British intelligence is one of the more inexplicable quirks of fate (ref. 15). All further discussions in Great Britain (and there would be many such) on whether the Germans had anything in the field of radio detection should have been superfluous—at the end of 1939 British intelligence had information on no less than three such systems in the German armoury. In his authoritative work on British Intelligence in the Second World War (ref. 16), Hinsley incorrectly writes that up to the middle of 1940 only one item of information on German radar development had been received – the result of inspection of the wreck of the Graf Spee. He does not mention the Oslo Report, although he was closely involved in British intelligence during the war, at the highest level (cryptanalysis at Bletchley Park). 

   From the historical perspective, it is clear that the first system mentioned, which detected the British bombers at 120 kms distance, is the Freya early warning radar. Data on the wavelength used are missing from the Oslo Report, but this, as its author says, can readily be determined by scanning the radio spectrum, radar-type signals being very characteristic. Additional evidence of the author’s expertise in this field is his remark that “special receivers capable of registering pulses of 10 –5 to 10 –6 seconds” (i.e., broadband receivers) are necessary.

   The date mentioned (beginning of September 1939) for the radar detection of bombers attacking Wilhelmshafen is intrigueing. The RAF operation mentioned here should not be mistaken for the disastrous daylight attack on German shipping by twenty-two unescorted Wellingtons of which only ten returned, as this took place on December 18th, 1939, after the Oslo Report was written. That attack was indeed intercepted by fighters that had been alerted on a German radar specialist’s private initiative (refs. 17, 18). The only operation that comes into consideration is the attack on the Schillig Roads by ten unescorted Blenheims, five of which were lost, on September 4th, 1939. The aircraft were indeed attacked by Bf109 fighters but I have not been able to find any evidence that radar was used to alert and direct the fighters in this particular case. German radar operators may of course have detected the bombers during that operation and a German radar specialist might have personally communicated the detection of the British aircraft to the Oslo Report author at some later moment, but as far as can be determined this was not an organized radar-controlled interception because there was as yet  no channel of communication between the German radar stations and the fighters.

   The second system mentioned, working at 50 cms, is obviously the Würzburg, the standard German precision radar of the war. The technical description contains an interesting detail that has not been mentioned in the post-war literature as far as I know and therefore warrants a special mention. The receiver is said to resemble what we now call a two-input AND gate: it is normally blocked and opens only when it receives two simultaneous signals. One is the received echo, the other is the original emitted pulse, which is sent through a continuously variable delay line (“artificial conductor”). By varying the delay, the distance to the target could be measured. This delay in a transmission line was part and parcel of standard radio theory at that time and was widely used in practice for directional aerials. Theoretically, this very clever idea would work, but practical implementation would not be easy and operation would be cumbersome. The actual Würzburg did not employ this principle but used display of the echo on a timebase (A-scope). Delay lines were later widely used in radar equipment to remove stationary objects from the display, in order to concentrate on the moving objects, but that development was still in the future.

   This variable-delay concept reflects the basic German radar philosophy, which differed considerably from the Allied approach. In the German view, radar was a method for precision measurement; hence the technique was called “Funkmess”. This is best exemplified in the subsequent German standard method for tracking aircraft, in which the positions of target and friendly nightfighter were measured separately by two Würzburg sets and the nightfighter was given course corrections to make the two independent data streams coincide in space and time. This correlation of two unrelated data streams required great precision: the two separate Würzburg radars had to be very accurately built and oriented (azimuth errors), carefully calibrated and very stable to avoid timebase drift (range errors). Great precision is indeed mentioned in the German text as an advantage of the method described. Such precision is unnecessary with a display of the PPI (plan position indicator) type, introduced by the British for nightfighter direction, where any inaccuracy inherent to the equipment applied to everything on the screen and was thus cancelled out. The PPI method was also faster in use and required less human effort.

   The Oslo Report mentions separate aerials for the transmitter and the receiver. These were indeed used in an early stage of development but the set that became operational had a single parabolic dish.

  This is the most important item in the Oslo Report and I will discuss its significance further in the Evaluation.

  9. Aircraft distance-measuring equipment

   This is another lucid description of a distance-measuring device that would be perfectly acceptable to a technical specialist in 1939. Its principle is closely related to that of the radio altimeter, with the difference that the reflected signal used by the latter is replaced by a re-radiated (and amplified) signal transmitted at a different frequency, the transponder principle. Note that the pilot of the aircraft cannot determine the distance himself, he is dependent on ground control for that information—as in the Oboe system developed later by the British for the same purpose, viz. blind bombing. 
In the historical perspective, this is identifiable as the Y-Gerät, which became experimentally operational in the autumn of 1940. Interestingly, this was the third and last blind bombing system introduced by the Germans; the two earlier systems (X-Gerät and Knickebein) are not mentioned in the Oslo Report. 

   10.  Torpedoes

   As regards the first type of torpedo mentioned, very long radio waves do indeed penetrate some distance into the water. Actually, the 3 kM (100 kHz) wavelength mentioned is still on the short side. The problem is that such very low frequencies require large aerials and high power for the transmitter. Such equipment could theoretically have been installed on ships, but for aircraft serious problems arise. Underwater radio control of torpedoes such as the Oslo Report describes is fraught with problems, therefore, and no such torpedo was developed. The acoustic self-guiding principle described is a different matter; it was perfectly feasible also in 1939 and indeed led to the Zaunkönig torpedo, first used in action in September 1943.

   As regards the magnetic fuze for torpedoes: this also was theoretically perfectly acceptable to British scientists. A magnetic fuze for sea mines had in fact already been developed by the British at the end of the First World War. The “earth inductor” mentioned in the Oslo Report had been a standard measuring-device in studies on the Earth’s magnetic field for a long time. In Germany, development between the wars had resulted in the availability of both a contact fuze (AZ) and a  magnetic fuze (MZ) for the standard G7a or G7e submarine torpedo (ref. 19)

   Proximity fuze

   The first portion, about the electrical bomb fuzes, does not so much describe fuzes as an electrical arming-device for bombs: the bombs automatically become “live” when released. This would appear quite acceptable in 1939.

   The second portion, about the electric time-fuze, describes an idea for a proximity fuze, a fuze that detonates the warhead at a prescribed distance from the target. The notion of nearby objects leading to imbalance among partial capacitances would be acceptable in 1939, but in practice the trigger as described would not work; more would be required in the way of electronic circuitry. Development of the fuze described therefore became a dead end and although several experimental types of proximity fuze were developed in Germany later on, they did not become operational. This was in contrast to events in Great Britain and the USA, where such development did lead to the introduction of the proximity fuze (VT-fuze) in 1943, one of the more successful Allied secret weapons (ref. 20).

   An expert detail is that the Oslo Report author not only mentions anti-aircraft application, but also the use against ground troops, with the shells automatically exploding at an optimum distance above the ground so as to spray the troops with lethal fragments. This would greatly appeal to 1939 gunners and it became a major boon to Allied artillery men during the 1944 Ardennes offensive, for instance.


   First, a general remark. In the German text, “April 1940” is mentioned no less than four times as a deadline for the introduction or completion of technical developments: a production deadline for the Ju-88, a deadline for the completion of the aircraft carrier, deadline for the implementation of a radar chain and a production target date for bomb fuzes. In 1939, an analyst might have deduced that some sort of critical event would take place by that date. With hindsight, one might be tempted to conclude that this referred to the start of operations in the West—the invasion of Denmark and Norway. But at the time the Oslo Report was written, the German plans for operations in the West were still in a state of flux: the eventual scenario for the campaign in France had not yet been conceived and the invasion of Scandinavia was not yet being planned at all. The reason why this particular deadline is repeatedly mentioned is not clear.

A Dichotomy

   If we examine the German text of the Oslo Report, it becomes evident that the brief excerpts in the post-war literature do not at all do justice to the whole story. Reading the original, the reader has the feeling of sitting on an intellectual see-saw, for the Oslo Report contains two entirely different categories of information.

   The first category is of a general military nature: the Ju-88 programme, the German aircraft carrier and the method of attacking fortifications. All three items can be characterised by a variety of adjectives ranging from ridiculous to spurious or insipid. Remarkably, these serious weaknesses in the Oslo Report have not been pointed out in the post-war references. Thus, the strong arguments in favour of those British intelligence experts who doubted the Oslo Report’s reliability have not been fairly presented and the modern reader might well underestimate the competence of the doubters. The omission of these serious shortcomings is most notable in R.V. Jones’s exposé—he writes that during the war, he continued to consult the Oslo Report, which indicates that he thought it highly reliable, but he does not mention that (for instance) a single phone call to British Naval Intelligence would have shown that the first German aircraft carrier was most assuredly not called Franken.  Jones’ presentation was, therefore, highly selective: he only mentioned those items (or even just those parts of the items) that turned out to be true—for example, he did mention the dive-bombing Ju-88, but not its surrealistic production figures.

   The second category is of a technical (predominantly electronic) nature and here the reader seems to pass a watershed: from amateurish to utterly competent. Suddenly, we are given technical details, sketches (which have not survived) illustrate the principles, there is a reference to a recent issue of the prestigious Bell Systems Technical Journal—just as a scientist will do in a peer-reviewed paper—and the text exudes confidence. Sometimes it even begins to resemble a tutorial, like a don telling his students “if you wish to counter this secret weapon, you simply broadcast interference on the same wavelength”. Again, this remarkable dichotomy in the Oslo Report has not even been hinted at in the post-war literature.

   But the difference in opinion between the doubters and the believers is easily resolved, because as I have already indicated, the Oslo Report contains inherent and irrefutable evidence against its being a plant, evidence that even in 1939 should have it made clear that the author was literally putting his head on the block: the revelation of the German radar developments.

A Secret Known to All

   For some reason, all parties working on radar in several countries thought they were the only ones to do so, although in 1939 the basic principles were known to any engineer or advanced radio-experimenter familiar with the open technical literature of the past decade. Even the very first experiments with “radio” by Hertz about half a century earlier had demonstrated that radio waves are reflected, and by 1936 experimenters in the then new field of television were quite familiar with the phenomenon. Pulsed radio signals had been widely used to determine the height of reflecting layers in the ionosphere. Directional aerials for transmission and reception were in general use for navigation and direction finding, for example, with several different types having been described in the public domain. In fact, the principles underlying radar were so self-evident that in the beginning of the Second World War, brief coaching was enough for South African, Canadian and Australian radio engineers to develop their own versions of radar from scratch in a very short time, using standard commercial components (ref. 21).

   Despite this, radar was regarded as the Mother of all Secrets by all involved, leading to such ludicrous consequences as German censors not erasing obvious highly directional aerials from pictures of warships made publicly available—because the technique was regarded as so secret that the censors were not informed that it was secret … (ref.22). As late as 1941 there was still disagreement among British experts on the question of whether the Germans did, or did not, have anything like radar (ref. 23). To some extent this may have been the result of arrogance—on the British side, Watson-Watt may well have been loath to concede that anybody else could be so clever as he himself  (ref. 24)—but, especially, the implications of this new technique were so major that wishful thinking may have got the better of reason.

   What the radar information in the Oslo Report amounted to should have been grasped immediately by any British intelligence specialist conversant with his country’s own developments in the field. If the tables could have been turned, we would have had the situation where a British scientist sent the following message to the Germans in 1939:

“The British have a radio detection system, broadcasting pulse-type signals that are reflected from objects like aircraft. The reflected signals are displayed on cathode-ray tubes and the distance is measured by the delay between the transmitted and received pulses. This is good for a range of up to 150 kms or so and the system is fully operational, covering the approaches to the British Isles. And by the way, several more types of such equipment working on different frequencies are in development."
   There is no possibility of such information being “given away” for deception purposes; we are not looking at a devious intelligence plant here, but at High Treason—not because the principles so clearly explained in the Oslo Report could be regarded as secret, but rather because the Report reveals their successful implementation. As I pointed out at its thirtieth anniversary (ref. 24), the Battle of Britain was not decided by the technical merits of the British Chain Home system—in fact, the Chain Home radar was technically already obsolete, in essence an update of Watson-Watt’s 1920’s thunderstorm detection system. Rather it was Air Marshal Hugh Dowding’s breadth of vision in the years prior to the war that led to a carefully worked out integrated operational system of British air defence—the first of its kind—that was a decisive factor in the outcome of the Battle of Britain.

Too Wide-Ranging Knowledge?

   One argument raised by the doubters in 1939 was that no single person could have knowledge of such a wide-ranging field of weapons technology as is discussed in the Oslo Report. Certainly that would be true if the author were a member of German military counter-intelligence, composing a “plant”. Cooperation between Navy and Air Force was very poor in Great Britain and the USA, but in Nazi Germany these two organisations were virtually at war between themselves. It was unthinkable that any component of the German armed forces would relinquish secret technical information to be used in a deception operation by a counter-intelligence officer of the Abwehr. Actually, the information in the Oslo Report is only incidentally wide-ranging in the sense that it discusses some projects of the German Army, the Navy and the Air Force. Rather, it is strongly focused: on electronic technology. Several major German companies, like Bosch or Telefunken, were involved in projects for all three forces and some scientists in leading positions in these industries will have had a wide-ranging overview—one such being the author of the Oslo Report. The doubters in Great Britain should have been aware of the fact that also in their own country, there were several people that did have such wide-ranging knowledge of British projects. One of these would be facing them across the table during sometimes heated discussions—R.V. Jones.

   To some extent, the unbalanced nature of the Oslo Report may explain British attitudes to it. The military information is amateurish; the technical information is highly professional. Thus, it would be logical if the assessment of the Oslo Report by the British in 1939 differed along the same dividing line: military intelligence professionals may well have tended to discount it because of the shortcomings in this respect, while the high technical quality was beyond their ability to appreciate. Amongst these participants in the drama, interest in the Oslo Report was slight to nil and the document vanished into a drawer (ref. 4). Technical specialists and scientists may have leaned towards the opposite attitude. Both parties had good arguments supporting their case, but the “leak” of the German radar developments should have clinched the matter.

Maximum and Actual Impact

   The Oslo Report is one of the most spectacular leaks in the history of military intelligence. At one stroke, several top-secret projects years in the making are forfeited and the technical information leaked is of high quality. To see what the maximum impact of these traitorous Seven Pages of Wisdom might have been, let us assume that the Oslo Report had come with a guarantee that all information was correct. As I have argued, the information on German radar development supplied is a guarantee that at least this information was not a hoax, but it does not prove that all the information in the Report is both correct and accurate. Let us also suppose that all possible countermeasures would have been taken by the British without delay. How would this have benefited them? And how does this compare to the actual countermeasures taken during the war?

   For the first three significant items, 3) remote-controlled glider, 4) autopilot and 5) remote-controlled missiles, no countermeasures were possible until the frequencies used for radio control were known. This had to wait until such data became available from additional leaks, by examination of captured material or by radio monitoring. Until then, the only British attitude could have been to “keep this in mind”. When such radio-controlled weapons were introduced by the Germans later on (Hs-293, Fritz-X), some ships were lost, but radio countermeasures were taken within a reasonably short time.

   For item 8) radar, the situation is similar. In the ideal case, the information would have made the British aware from the outset that the Germans had radar, but examination of the wreck of the Admiral Graf Spee should already have sufficed to do this. For the Freya, no frequency is given, for the Würzburg the wavelength is said to be 50 cms. A search receiver for such (then) ultrashort wavelengths could have been constructed in the ideal case. In the event, there was a delay until the beginning of 1941 before Würzburg signals were identified (ref. 26). The consequences of this delay were not major, however: such radar equipment as the Freya and Würzburg was primarily a defensive weapon and only became a real threat when the British bomber offensive gained momentum by 1942. By then, the existence of German radar was no longer in doubt anyway.

   For item 9) Y-Gerät, the situation is different: this was an offensive weapon and from the very beginning the possibility of a devastating bombing attack was uppermost in the minds of all belligerents. But the first blind-bombing techniques introduced by the Germans were the X-Gerät and the Knickebein, which were of an entirely different nature and are not mentioned in the Oslo Report. Countermeasures against the Y-Gerät would have had no effect against these, therefore. In the event, the German secret blind-bombing aids were countered swiftly, the one major failure leading to the severe damage to Coventry on November 14th, 1940.

   For item 10), the torpedoes, the situation would have been as follows. Magnetic mines were a British development at the end of the First World War and German magnetic mines were already captured intact by the British in November, 1940 (ref. 27, 28). Magnetic torpedo fuzes were a logical extension of the tecnique. The countermeasure, “degaussing”  of ships’ hulls, taken in 1940, was also effective against magnetic torpedo pistols. 
As for acoustic torpedoes: the Zaunkönig acoustic torpedo was introduced in September 1943 and although some ships were lost, a countermeasure consisting of a noise generator (ref.29) was soon introduced. It would of course have been most unwise to operate such a countermeasure before the Germans introduced the acoustic torpedo; one had to wait until positive proof of its operational introduction had been obtained—which means that ships should have been sunk by one... The advantage in the optimum case could therefore not have been very major.

   As regards item 11), the proximity fuze, this was not introduced by the Germans during the war. Had the principle described worked without additional electronics (and it would not have done so), no countermeasures would have been possible. Electronic countermeasures against a German equivalent of the Allied proximity fuze (i.e., one that had a built-in transmitter and receiver) would have been possible, but the frequency used would have to be known and this would again depend on a further leak, the capture of a “dud” or frequency monitoring while being under artillery fire— the last  option surely being an exhilarating experience. 

   This leads us to the conclusion that despite the good intentions of the author of the Oslo Report and the immense risk he was willing to take, the impact could not have been markedly greater even if the Oslo Report had immediately been accepted as truth and acted upon by the British. Its hypothetical maximum impact could primarily have been as an alert: “keep this in mind”. That was precisely what was done by at least some British intelligence and countermeasures experts, with little opportunity being lost.

   In this respect, there was a fundamental difference between the Oslo Report and the other major Allied intelligence coup, cryptanalysis. The solutions of German and Japanese cryptography came with an integral guarantee of authenticity, were often open to swift verification and, above all, could find immediate application in the form of tactical or strategic countermeasures (e.g., routeing of convoys). Whereas German secret weapons obviously did not win the war, the Allied secret weapon of cryptanalysis certainly was a major contributing factor in victory for the Allies.

   Looking back, the conclusion must be that in World War Two, except for centimetric radar, secret weapons were not militarily decisive in the long run. Even for the most secret of all, the atomic bomb, its decisive role continues to be disputed by some. In the end, it is a combination of superior tactics, strategy and resources that can indeed bring victory. Perhaps there is a lesson to be taken to heart in this time of hi-tech weaponry versus irregular and often urban warfare? 


   Stephen Walton, IWM Duxford, U.K. made this study possible by tracing the copy of the original text of the Oslo Report. Dr. Gregory Good, West Virginia University, U.S.A. and Shaun J. Hardy, Librarian, Carnegie Institution of Washington, DTM-Geophysical Laboratory Library, U.S.A., kindly supplied information on the “earth inductor”. Dr. Peter Webber kindly commented on the draft.

Author Biographical Data 

   The author was a consultant to hi-tech industries including defence-oriented companies and research centres for over 40 years. Living as a youngster in the Netherlands occupied by Germany during World War Two, he saw many of the secret weapons mentioned in the Oslo Report in action.

Frithjof A.S. Sterrenburg
e-mail: fass@wxs.nl
1) Reginald V. Jones, Most secret war. British Scientific Intelligence 1939-1945. Coronet Books, Hodder & Stoughton, London, 1979, p. 105-108

2) Brian Johnson, Streng Geheim. Wissenschaft und Technik im Zweiten Weltkrieg. Wiener Verlag, Wien. (Author’s note: this is a German translation of the book based on the BBC TV series, 1978, which included personal interviews with some of the major participants in the subject).

3) Louis Brown, A Radar History of World War II. Technical and Military Imperatives. Institute of Physics Publishing, Bristol, UK and Philadelphia, USA. 1999

4) Letter Boyes quoted in Jones, Most Secret War, p. 108

5) Jones, Most Secret War, p. 454

6) Reginald V. Jones, Reflections on Intelligence, Heinemann, London 1989, p. 325-326

7) Peter C. Smith, Dive Bombers in Action. Blandford Press, London, New York, Sydney, 1988, p. 16

8) Cajus Bekker, The Luftwaffe War Diaries. The German Air Force in World War II. Birlinn, Edinburgh, 2001, p. 65

9) William Green, Warplanes of the Second World War, Bombers and Reconnaissance Aircraft, Vol. 10. Mac Donald, London, 1968, p. 87

10) Cajus Bekker, The Luftwaffe War Diaries, p. 376

11) Cajus Bekker, The Luftwaffe War Diaries, p. 91

12) Reginald V. Jones, Most secret war, p. 437

13) Reginald V. Jones, Most secret war, p. 544

14) Brian Johnson, Streng Geheim, p. 176, p. 184

15) Reginald V. Jones, Most secret war, p. 136

16)  F. H. Hinsley, British Intelligence in the Second World War, HMSO, London, Second Impression (with revisions) 1994, p. 164 (reformat this line)

17) Louis Brown, A Radar History of World War II,. p. 103

18) Max Hastings, Bomber Command, Michael Joseph, London, 1979, p. 15-35

19) Dan Van der Vat, Stealth at Sea, Houghton Mifflin Company, Boston/New York, 1995, p. 176

20) Louis Brown, A Radar History of World War II, p. 174-186

21) Louis Brown, A Radar History of World War II, p. 209

22) Louis Brown, A Radar History of World War II, p. 450

23) Reginald V. Jones, Most secret war, p. 252

24) Louis Brown, A Radar History of World War II, p. 223

25) Frithjof A.S. Sterrenburg. Electronica en de Battle of Britain, Radio Bulletin, Aug. 1970, p. 321-323

26) Brian Johnson, Streng Geheim, p. 108

27) Reginald V. Jones, Most secret war, p. 120

28) Brian Johnson, Streng Geheim, p. 251-255

29) Brian Johnson, Streng Geheim, p. 243

The Man Who Delivered the Report

   The identity of the person that was responsible for the production and delivery of the Oslo Report has been a mystery for a long time. In 1989 however, it was revealed to the public by Dr. R.V. Jones. Nothing was readily available in German publications and only very little elsewhere, until the May 2003 IEEE proceedings gave a clear statement.

   Finally we know who he was. Some extracts: A lecture on Scientific Intelligence, delivered by Dr. R.V. Jones in 1947, released by CIA in 1994—"At times of alarm, such as followed the outbreak of war and Hitler's speech, casual sources crop up in large numbers. These are mainly people who, under the stress of the situation, think that they have information of value to the country."

   Jones elaborated, "Much of the information is useless, but in the days following Hitler's speech one casual source came up whose information was of remarkable interest. It happened in this way. Our naval attache in Oslo received an anonymous letter telling him that if we would like a report on German technical developments, all we need do was to alter the preamble on our German news broadcast on a certain evening, so as to say, 'Hullo, hier ist London,' instead of whatever we usually said. The writer would then know that we wanted the information and would send it to us. We duly altered the preamble, and the information arrived. It told us that the Germans had two kinds of radar equipment, that large rockets were being developed, that there was an important experimental establishment at Peenemünde, and that rocket-driven glider bombs were being tried there. There was also other information-so much of it in fact that many people argued that it must have been a plant by the Germans, because no man could possibly have known of all the developments that the report described. But as the war progressed and one development after another actually appeared, it was obvious that the report was largely correct; and in the few dull moments of the war I used to look up the Oslo report to see what should be coming along next."

   PROCEEDINGS OF THE IEEE, VOL. 91, NO. 5, MAY 2003—Hans Ferdinand Mayer was born on October 23, 1895, in Pforzheim, Germany, which is located halfway between Stuttgart and Karlsruhle. After receiving a leg wound in his first action in World War I (1914), he studied physics and mathematics at the Technische Hochschule in Stuttgart and went on to the University of Heidelberg to become a research assistant to Philipp Lenard (1862–1947), a Nobel Prize winner in physics (1905).

   He received his doctorate in 1920, with his dissertation concerning the interaction of slow electrons with molecules. He continued working as a research assistant for Lenard until 1922, and then joined Hause-Siemens. He became Director of Siemens Research Laboratory in 1936. Except for interludes during and after World War II, he worked for Siemens until his retirement in 1962. He published 25 technical papers during his life and secured over 80 patents. He received an honorary doctorate from the Technische Hochschule in Stuttgart in 1956, the Gauss–Weber Medal from the University of Göttingen, the Philipp Reis award from the German Post Office in 1961, and the Ring of Honor from the VDE in 1968. Mayer died on October 16, 1980, in Munich.

   As recognized as he was for his technical work, Mayer’s personal life perhaps had more impact. As described Mayer secretly leaked to the British in November 1939 all he knew of Germany’s warfare capabilities, particularly concerning electronic warfare. Because he represented Siemens as a technical expert in negotiations with companies outside Germany, he had the opportunity to travel widely about Europe.

Hans Ferdinand Mayer

   While in Oslo, Norway, he typed and mailed a two-page report of what he knew and mailed it to the British Embassy in Oslo. Because Mayer wrote it anonymously, the British, led by Reginald Jones, had to determine the report’s accuracy. Jones found what became known as the Oslo Report to be a technically knowledgeable person’s description of what he/she knew (although it contains some errors). Only after the war did Jones determine that Mayer was the “Oslo Person.” Mayer did not even tell his family of his role in the Oslo Report until 1977. He requested that his contribution
not be made known until after his and his wife’s death. Jones described Mayer’s contributions in 1989 [8] and a newspaper feature appeared that same year. During the war, Mayer continued working at Siemens, until he was arrested in 1943 by the Gestapo for listening to the BBC and speaking out against the Nazi regime.

   He was saved from execution by his doctoral advisor Lenard, despite Lenard being a strong supporter of the Nazis (he first met Hitler in 1926) and being anti-Semitic to the extreme (so much so he could not believe any Jew’s physics, Einstein in particular). Mayer was put into the Dachau concentration camp, and later moved into four others during the remaining years of the war. After the war, he joined the electronics research effort at Wright-Patterson Air Force Base, Dayton, OH, which at the time was the U.S. Air Force’s primary research laboratory. He left the laboratory in 1947 to become Professor of Electrical Engineering at Cornell University. It is during this time he wrote his letter describing Helmholtz’s role in developing equivalent circuits. After the Federal Republic was established in 1949 and Siemens was returning to its pre-war prominence, he returned to Germany in 1950 to work with Siemens in Munich.

Thanks to Cor Lulof




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