The Oslo Report

The British Naval Attaché at the Oslo Legation, Rear-Admiral H Boyes, received an anonymous package at the beginning of November 1939 detailing German secret weapons development. The document contained information on such things as radar development, remote controlled gliders, acoustically and magnetically detonated torpedoes, and long-distance air navigation techniques with suggested countermeasures. The report also revealed Peenemünde and Rechlin as Wehrmacht experimental weapons test sites.

Three copies of the Oslo report with drawings and English translation were forwarded to the Director of Naval Intelligence on 6 November 1939.

After the war it was established that the report had been supplied by German mathematician and physicist Hans Mayer.

The first part of the report is reproduced below and includes copies of the drawings.






Ju 88 is a twin engined long distance bomber and has the advantage that it can be used as a dive bomber. Several thousand, probably 5000, are being manufactured monthly. By April 1940 25 - 30,000 of this type are to be ready.


The first German aircraft carrier is at Kiel. She is to be ready by April 1940 and is called the "Franken".


The Navy is developing remote controlled gliders, i.e. small aeroplanes with a span of about three metres and three metres in length, carrying a heavy explosive charge. They are not driven by motors and are dropped from aeroplanes from a great height. They contain:-

a) An electric altimeter, similar to the wireless altimeter (Bell System. Techn. Journal Jan.39. p.222) which causes the glider to straighten out about three metres above the water. Then it flies horizontally powered by rockets.

b) A remote controlled steering gear actuated by ultra-short waves in the form of tele­graph signals, by which the glider can be steered to the left or to the right or straight ahead either from a ship or an aeroplane.

In this way the glider is intended to be steered against the side of an enemy ship and the explosive charge dropped so as to explode below the water line. The secret number is FZ 21 (Ferngest. Flugzeug - remote controlled aim-plane). The testing grounds are in Peenmünde, at the estuary of the Peene, near Wolgast, in the neighbourhood of Greifswald.


Bearing the secret number FZ 10 an autopilot (remote controlled aeroplane) is being developed which can be controlled from a manned aeroplane, for example to destroy balloon barrages. The works are in Deepensee near Berlin.


The Army Ordinance Office (HWA) which is the experimental department of the army, is engaged upon the development of projectiles of 80 cm calibre. In them a rocket drive is used, they are steadied by a built-in gyroscope. The difficulty in a rocket drive lies in the fact that the projectile does not fly along a straight course but in uncontrollable curves. Therefore it has a wireless remote control with which the firing of the explosive in the rocket is regulated. This development is a in an elementary stage and the 60 cm projectiles are intended for future use against the Maginot Line.


This is a small place on the Müritz Lake (Müritzsee) to the north of Berlin. Here is the laboratory and experimental station of the air force. A useful target for bombers.


Experience in the field against the Poles has shown that an ordinary attack on strong points does not meet with success. Polish strong points were therefore enveloped in a smoke screen from smoke shells (Gasgranaten) in such a way that the smoke screen was carried like a curtain further and further into the strong points. Directly behind the smoke German flame throwers advanced and took up positions in front of the strong points. The strong points proved powerless against the flame throwers and the garrison either perished or were made prisoners.


In the attack of the British fliers on Wilhelmshafen at the beginning of September the English aeroplanes were detected when still 120 km from the German coast. Along the whole coast of Germany short wave transmitters with an output of 20 kw are placed, which send out quite short impulses at 10-5 second intervals. These impulses are reflected by the aeroplanes. Near the transmitter is a wireless receiver tuned in on the same wavelength. It is here that the reflected wave is picked up and registered on a "Braun" valve. By the difference between the transmitted impulse and the reflected impulse one can calculate the distance of the aeroplane. As the trans­mitted impulse is much stronger than the reflected one, the receiver is switched off during the transmitting of the impulse. (Meaning uncertain) The transmitted impulse is registered on the "Braun" valve with a local mark. In conjunction with the Ju 88 programme similar transmitters will be installed all over Germany by April 1940.

Protective Measures. By using special receivers which can pick up impulses of 10-5 to 10-6 second intervals one must determine the wave length of the impulses sent in Germany and then send interfering impulses on the same wave length. These receivers can be on land, so can the transmitters as this method is very sensitive.

While this method has been introduced to a great extent another invention is being prepared working on 50 cm wave lengths. (See Fig, 1). The transmitter T sends out short impulses which are aimed by an electrical concave mirror. The receiver R is next to the transmitter and also has a directional aerial. This picks up the reflected impulse. T and R are connected by an artificial circuit of which the relaying time is alterable. This artificial circuit has the following purpose:-

The receiver is closed to ordinary waves and cannot pick up impulses. The impulse which is transmitted by wireless from T is also carried along the artificial circuit and makes the receiver receptive for a very short time. If the time taken on the artifi­cial circuit is equal to the time taken for the reflected wireless impulse, the latter can be registered on the "Braun" valve. One can, for instance, very accurately measure the distance of an aeroplane and it is very insensitive to interference as the receiver is only alive for very short periods.


When pilots fly to attack an enemy country, it is important for them to know how far they are from their base. For this purpose the following invention is being developed at Rechlin:-

At the base there is a wireless transmitter (6 metre wave) which is modulated to a low frequency "f". The aeroplane which is a distance "a" away, receives the 6 metre wave and obtains, after demodulation, the low frequency "f". With this low frequency he modulates his own transmitter which has a somewhat different wave length. The thus modulated wave of the aeroplane is received at the base and demodulated. The low frequency "f" thus obtained is compared with the local low frequency. They differ from each other by a phase angle (Phasenwinkel) 4 Pi fa / c (In which let a = distance of the aeroplane; c = speed of light). By measuring the phase one can then measure the distance of the aeroplane and inform the plane as to its position. To ensure accuracy in the measurement the phase angle must remain below 2 Pi. Therefore one chooses a low frequency "f", e.g. 150 pps then for 1,000 km the phase angle equals 2 Pi . With so low a frequency one cannot achieve great accuracy. Therefore one sends at the same time a second, higher, frequency, e.g. 1.500 pps and compares the phase angle of this also. Thus 150 pps may be called a rough measurement while 1.500 pps is a precision measurement.


The German Navy has two new types of Torpedo:-

a) One wants, for instance, to attack a convoy from a distance of ten kilometres. These torpedoes have a wireless receiver which can pick up three signals, one can steer the torpedo to the left, to the right, or straight ahead, either from the ship firing the torpedo or from an aeroplane. Long waves are used, which can satisfactorily penetrate water wavelength of the order of three kilometres. These are modulated with short sound waves which actuate the steering of the torpedo. In this way the torpedo would be steered into close proximity of the convoy. In order to hit the ship two acoustic receivers (microphones) are built into the head of the torpedo which constitute a direction finder. The direction of the torpedo is so controlled by this receiver that it directs itself to the source of sound. When therefore the torpedo has been steered by wireless within a few hundred metres of the ship it automatically steers itself towards the ship, as every ship makes acoustic sounds by its machinery. One can fairly easily protect oneself against them by acoustic and wireless interference signals.

b) The second type of torpedo is probably that with which the "Royal Oak" was sunk. These do not explode against the ships side but under the hull. The firing of the explosives is attained magnetically and is based upon the following principle:-

(See fig. 2.) The vertical construc­tion of a magnetic field is approximately the same throughout, but is altered by the ship "S" so that at points "A" and "0" there is a weaker field while at point "B" there is a stronger field. A torpedo coming from the left, therefore, first runs in a normal field, then in a weaker one and so on. In the head of the torpedo there revolves an armature on a horizontal axis, rather like an earth inductor. At the clips of this armature a direct current is generated in proportion to the vertical construction of the magnetic field. In line with this current lies a contrary tension of equal strength so that no current can flow while the torpedo is in a normal magnetic field. When, however, the torpedo reaches point "a" the magnetic field is weaker and the tension on the revolving armature lessens. The two opposed tensions are now unequal, a current flows which actuates a relay which releases the firing. The delay action is set in such a way that the explosion occurs directly underneath the ship's hull.

Perhaps one can protect oneself against such torpedoes by stretching a cable alongside the ship approximately at the depth of the ship's keel and as far away from the hull as possible. If one sends a suitably selected direct current through this cable one can also produce a magnetic field with danger point "A" far away from the ship. Thus the torpedo would explode too soon. Perhaps it is also possible, by using suitably selected compensating armatures, to equalise the disturbance of the magnetic field cause by the iron mass of the ship.


Oslo Report drawings

[Source: TNA ADM 1/23905, transcribed by]