Oslo report

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The Oslo Report, written by Hans Ferdinand Mayer on November 1,2, 1939 during a business trip to Oslo, Norway, described several German weapons systems, current and future. He anonymously mailed the Report as two letters to the British Embassy in Oslo, where they were passed on to MI6 in London for further analysis. They proved to be an invaluable resource to the British for developing counter-measures, especially to navigational and targeting radars, and contributed to the British winning the Battle of Britain.

Contents 1 Background 2 Report Contents 2.1 Ju 88 Program 2.2 The Franken 2.3 Remote controlled gliders 2.4 Autopilot 2.5 Remote-controlled shells 2.6 Rechlin 2.7 Methods of attacks on bunkers 2.8 Air raid warning equipment 2.9 Aircraft rangefinder 2.10 Torpedoes 2.11 Electric fuzes for bombs and shells 3 Divulging the Report and the Author 4 References 5 Bibliography

[edit] Background

Hans Ferdinand Mayer received his doctorate in physics from the University of Heidelberg in 1920. After spending two years as a research associate there in his doctoral supervisor's (Philipp Lenard) laboratory, he joined Siemens in 1922. He became interested in telecommunications and joined Siemens's communication research laboratory, becoming its director in 1936. Because of this position, he had contacts all over Europe and the United States and had access to a wide range of information about electronics development in Germany, especially in the military sector. After Hitler invaded Poland on September 1, 1939, he decided to divulge to the British as much as he could about military secrets to defeat the Nazi regime. He arranged a business trip to Scandinavia in late October 1939. He arrived at his first scheduled stop, Oslo, Norway, on October 30, 1939 and checked into the Hotel Bristol. He borrowed a typewriter from the hotel's porter, donned white gloves and typed the seven-page Oslo Report in the form of two letters over two days. He mailed the first on November 1, the second the next day including with it a prototype proximity fuze, to the military attaché in the British Embassy in Oslo. He also attached a note to the second letter, asking that the BBC change the introduction to its nightly newscast to Germany on November 20, 1939 from "Hello, this is London calling" to "Hello, hello, this is London calling" to acknowledge receipt. He also wrote a letter to his longtime British friend Henry Cobden Turner, asking him to communicate with him via their Danish colleague Niels Holmblad. This indirect communication path was required since Britain and Germany were at war, but Denmark was neutral. Mayer continued his travels to Denmark to visit Holmblad, asking if he could relay information between himself and Turner. Holmblad readily agreed, but once Hitler invaded Denmark on April 9, 1940, this communication route was no longer feasible. Mayer then returned to Germany. Although Mayer was arrested by the Gestapo in 1943 and was imprisoned in concentration camps until the war ended, the Nazis never knew of the Oslo Report.

The Report arrived on the desk of Captain Hector Boyes of the Royal Navy, stationed as the Naval Attaché in the British embassy in Oslo. He quickly appreciated its importance and forwarded it to MI6 in London. Analysts there thought it contained too much information to be believed, but it was sent to Reginald Victor Jones, a young Ph.D. physicist recently appointed to MI6 to analyze scientific intelligence. Jones argued that despite the breadth of information and a few inaccuracies, the technical details were correct and argued that all the electronic systems divulged therein be further explored. In a 1940 report, Jones summarized his thoughts.^[1]

The contribution of this source to the present problem may be summarised in the statements that the Germans were bringing into use an R.D.F. [ Radio Direction Finding, the British name for radar] system similar to our own,... A careful review of the whole report leaves only two possible conclusions: (1) that it was a "plant" to persuade us that the Germans were as well advanced as ourselves or (2) that the source was genuinely disaffected from Germany, and wished to tell us all he knew. The general accuracy of the information, the gratuitous presentation of the fuze, and the fact that the source made no effort, as far as it is known, to exploit the matter, together with the subsequent course of the war and our recent awakening with Knickebein, weigh heavily in favour of the second conclusion. It seems, then, that the source was reliable, and he was manifestly competent.

In his 1989 book,^[2] Jones summarized the importance of the Oslo Report.

It was probably the best single report received from any source during the war. ...Overall, of course, the contributions from other sources such as the Enigma decrypts, aerial photographs, and reports from the Resistance, outweighed the Oslo contribution, but these were all made from organizations involving many, sometimes thousands of individuals and operating throughout most of the war. The Oslo Report, we believed, had been written by a single individual who in one great flash had given us a synoptic glimpse of much of what was foreshadowed in German military electronics.

[edit] Report Contents

The typed report is seven pages long. The original is thought to be lost, but a typed copy (in German) can be found in the Public Records Office.^[3] The Report has been published twice in translation to English.^[4][5] The section headings given here correspond to those in the Report. Some of the information Hans Ferdinand Mayer heard was second-hand and it proved to be false.

[edit] Ju 88 Program

The Junkers 88 light bomber production levels are stated to be 5,000 per month, with a total of over 25,000 predicted to be produced by April 1940.

The Report grossly overexaggerated the production levels and the total production. The date, April 1940, is significant; it corresponds to Hitler's invasion of western Europe.

[edit] The Franken

The Report describes the Franken as the German navy's first aircraft carrier and its harbor as Kiel. The first aircraft carrier was in fact the Graf Zeppelin, which was indeed located in Kiel. Construction of the carrier was never completed.

[edit] Remote controlled gliders

Unknown to the Allies, the German Luftwaffe was developing rocket-propelled aircraft that could be controlled via radio signals. The pilot of a bomber would use a joystick to guide visually the explosive-laden airplane to a target. Mayer noted the similarities of the guidance system to an American low-altitude altimeter. Testing of this weapons system was specifically noted as occurring at Peenemünde.

This system was known as the Henschel Hs 293 and saw action during World War II in the Mediterranean. The system proved to be tricky for the pilot to control since he had to fly his own airplane at the same time during combat situations. Citing Peenemünde provided the British the first notice that advanced rocketry research was occurring there. The British bombed the facility in August 1943.

[edit] Autopilot

Here, Mayer briefly described another remote-controlled system, this time for an aircraft instead of for a rocket. It is likely that Siemens was developing the control systems for both projects from a common design.

[edit] Remote-controlled shells

Remote-controlled artillery shells (80 cm) were under development by the German Army. They would be rocket-propelled and have gyroscopic stabilization. Development work was explicitly mentioned as being in its earliest stages but are intended to be used against France's Maginot Line.

Shells travel much too fast and the artilleryman can't see the target. This system was never deployed. However, the mention of the Maginot Line does indicate that Germany intends to invade France.

[edit] Rechlin

Rechlin is a small town located on the Lake Müritz north of Berlin. Mayer noted that it is the main Luftwaffe research center and should be a "rewarding target" for bombers.

[edit] Methods of attacks on bunkers

Mayer noted that the Wehrmacht stormed gun emplacements during the invasion of Poland by using smoke shells. Once the men defending the emplacements could not see, soldiers armed with flame throwers attacked.

Revealing these tactics employed by the Wehrmacht during its Blitzkrieg of Poland is perhaps the most mundane information provided by the Oslo Report.

[edit] Air raid warning equipment

The technical characteristics of German early-warning radar systems (power, pulse duration, range) were described in some detail, along with counter-measures that could exploit the radar system's vulnerabilities. Mayer did not know the last critical piece of information: the wavelength. He also noted that this system was being installed on Ju 88 bombers, the first instance of an airborne radar. Again, he mentioned the date of April 1940 as the deadline for installation of this radar. He described a similar second system that was under development at the time that operated at a 50 cm wavelength.

The section of the report revealed Mayer's depth of knowledge of radar technology. The operational radar principle he revealed—transmitted short burst of energy, measuring the time-of-flight and calculating range from it—was known by the British and was in fact being used in its Chain Home early warning radars. Revealing how the full details of the system under development allowed the British to invent a simple countermeasure they called Window. Window was called chaff by the Americans—it consisted of long strips of aluminium foil—having a length designed to optimally reflect the German 50 cm radar signals, jamming them. It turned out that 50 cm was a standard wavelength that all German defensive radars used, which made Window a very effective way of blinding all their defensive radar systems throughout World War II.

[edit] Aircraft rangefinder

Mayer described a system for navigating German bombers to their targets being developed at the radar research group at Rechlin. This system used two modulating sine waves to disambiguate the aircraft's range using phase differences. He divulged the radar's wavelength and the modulating frequencies.

The development system Mayer described used a single radar beam to accurately locate a bomber's position. When the war began, German navigational systems employed two radars that triangulated the position. Not only was this system operationally simpler, it allowed the radar base station to trigger the bomb release when it reached the target, easing the bomber crew's work. Once deployed, this radar system was code-named the "Y-system." With Mayer's information, the British had counter-measures ready, fooling the radar into producing false locations. Consequently, bombers dropped bombs far off-target, many times into the sea.

[edit] Torpedoes

The German Navy had two novel kinds of torpedoes. The first was remote-controlled from the launch site, be it a submarine, ship or airplane, until it neared the targeted ship. Once close enough, microphones mounted in the torpedo head homed onto the sounds a ship's engines make. Mayer generally suggested the counter-measure approach of using a jamming signal. The second system had been used in the attack on the British ship, the Royal Oak, early in World War II. It exploited the deviations a ship's metal hull produced in the Earth's magnetic field. Once a significant deviation is sensed, a time-delay fuze ignited the torpedo.

[edit] Electric fuzes for bombs and shells

This section comprised the second letter Mayer wrote and described proximity fuzes used in bombs and artillery shells. He even enclosed a prototype he had secreted out of Germany in his mailing. Both systems exploited the change in capacitance the bomb or shell experiences when it nears a metallic object. Mayer revealed where the proximity fuzes were being manufactured.

The proximity fuze became one of the deadliest technologies developed during World War II. Anti-aircraft artillery no longer had to directly hit the airplane; it only had to come close enough for the shells to explode. The British quickly evaluated the design and found it to be unreliable. However, it inspired the radar-based proximity fuze developed by the Americans that proved far more effective than the German technology Mayer described.

[edit] Divulging the Report and the Author

On February 12, 1947, Jones gave an invited talk to the Royal United Service Institution that publicly revealed for the first time the existence and importance of the Oslo Report.^[6]

It [the Oslo Report] 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 be a plant by the Germans, because no one man could possibly have known all of 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.

This part of his talk caught the eye of the press and it was widely publicized. He revealed some of the Report's contents, holding back many details to test anyone claiming authorship. But neither Henry Cobden Turner nor Mayer heard of the talk at the time.

By chance, not only were both Turner and Jones on the same voyage of the Queen Mary in 1953, they also sat at the same dinner table one evening. They found much in common and Jones invited Turner to a dinner at his London club. On December 15, 1953 the dinner was arranged, during which one of Jones's friends, Professor Frederick Norman of King's College London, excitedly shouts "Oslo!!". Turner and Norman privately tell Jones over after-dinner drinks that Turner had heard from his old German friend, Hans Ferdinand Mayer, at the beginning of the war in a letter written from Oslo. Upon learning of Mayer's background and position at Siemens, Jones decided to open a correspondence with Mayer using Turner as a middleman.

Jones and Mayer met at a 1955 radar conference in Munich and had dinner with Turner at Mayer's house. Jones quickly determined that Mayer had indeed written the Oslo Report. They agreed that immediately divulging who had written the Oslo Report would serve no purpose and both agreed to silence. They continued to exchange letters, with Mayer providing more details about how he wrote it. Jones decided to write a book about his wartime scientific intelligence work for MI6, but it did not appear until 1978. In it, he discussed how he used the Oslo Report, but did not reveal the author.^[7]

Inevitably, the question will be asked regarding my own ideas about the identity of the Oslo author. I believe that I know, but the way in which the identity was revealed to me was so extraordinary that it may well not be credited. In any event, it belongs to a later period, and the denouement must wait until then.

Mayer died in 1980 without being publicly acknowledged as the author. Jones's sequel, published in 1989, revealed the author's identity.

[edit] References

[edit] Bibliography

• Louis Brown, 1999. A Radar History of World War II: Technical and Military Imperatives, Bristol: Institute of Physics Publishing, ISBN 0-7503-0659-9.
• Don H. Johnson. Scanning Our Past - Origins of the Equivalent Circuit Concept: The Current-Source Equivalent, Proc. IEEE, 91:817--821, May 2003.
• Reginald V. Jones, 1978. Most Secret War: British Scientific Intelligence 1939--1945. London: Hamish-Hamilton, ISBN 0-241-89746-7. Published in the United States as The Wizard War: British Scientific Intelligence 1939--1945, New York: Coward, McCann & Geoghegan, ISBN 0-6981-0896-5.
• Reginald V. Jones, 1989. Reflections on Intelligence. London: Heinemann, ISBN 0-7493-0474-X.