A note dropped through a private door in Oslo barely two weeks after the Second World War led to one of the most remarkable documents of the war – the Oslo Report. The note was sent to Captain (later Rear Admiral) Hector Boyes, Britain’s naval attaché in Norway. Its message was brief: if Britain wanted inside knowledge on Hitler’s secret scientific and technical plans, the BBC should alter the opening words of its German broadcasts.
The BBC wording was altered and the attaché received a seven-page document containing such remarkable material that the three government ministries responsible for the armed services – the War Office, Admiralty and Air Ministry – turned it down. Enemy propaganda was the general view of its contents. The three Services did not even bother to keep their copies. But one man who received it when it arrived in London was Professor RV Jones, the Air Ministry Assistant Director of Intelligence (Science). He kept his copy.
According to the Oslo Report, among different technical developments in which Germany was engaged was a remote-controlled, engine-less glider, code number FZ21 – Ferngesteuerte Zielflugzeug (remote-controlled target-aircraft) – and a pilotless aircraft, code number FZ10. The document added: ‘The testing range is at Peenemünde, at the mouth of the Peene, near Wolgast, near Greifswald.’ This was the first time that Peenemünde had been brought to the attention of Britain’s scientific and intelligence communities. And it would be more than four years before British experts found that this was the V1 or ‘doodlebug’ that was to rain down on London. Also known as the Fieseler Fi 103, it used a simple pulse jet engine, and an autopilot to regulate height and speed. It was two Enigma decrypts of September 1943 that finally convinced Professor Jones that the enemy was constructing two special weapons, later known as the V1 and the V2. Of such importance were these developments viewed in London that a special committee – codenamed Operation Crossbow – was set up to investigate it.
The Germans had been working on these special weapons long before the war. Experiments had been conducted as far back as 1932 at the Army experimental range at Kummersdorf West, about seventeen miles south of Berlin. The first launch tests in the Baltic, on the small island of Greifswald Oie, north of the island of Usedom, in the Peenemünde area, were in December 1937. It rose to sixty miles vertically and went at a maximum speed of 3,600 mph and hit its target at between 2,200 and 2,500 mph. A number of rockets were designed (codenamed A1 – A5), with A4 becoming the V2 – the ‘A’ standing for ‘Aggregat’, meaning ‘unit’ or ‘series’. The ‘V’ originally stood for Versuchsmuster (experimental type), but eventually became ‘Vergeltungswaffe’ or ‘reprisal weapon’. Trial launches commenced at Peenemünde in June 1942. Hitler had made a speech on secret weapons in September 1939, and went hot and cold on the project, sometimes sceptical, and finally enthusiastic. He eventually saw the V-weapons as a means of reversing the tide of war, hopefully enabling him to snatch victory from the jaws of impending defeat. In 1942 the project was revived and became known as FZG76 (Flakzielgerät or anti-aircraft target apparatus), which subsequently took the name V1. In January 1943, an RAF PRU – Photo Reconnaissance Unit – in a flight over Peenemünde confirmed that extensive construction was taking place. At the same time intelligence was coming in of a German capability of hitting Britain with the V1 from sites in France. Eventually a major launch site was discovered by PRU at Watten, near St Omer in the Pas de Calais, at Wissant and Bruneval, near Fécamp.
It was carelessness by Luftwaffe signals operators, using their operational Brown cipher, which gave away the V1 plots from the Baltic which provided height, speed, range and reliability of the V1 so accurately that Professor Jones was able to predict with absolute precision that forty per cent would reach the London area. Brown, which, after the invasion of Russia had declined in importance, began to come back into its own in 1944 with its bearing on V-weapon activities. The main transmitting stations were on the Baltic coast and were often inaudible to the English intercept stations. However, Wick in Scotland, which was fitted with a suitable rhombic aerial, could intercept the main frequency and further cover was provided by another Scottish outstation at Montrose. A German Army Netz – a W/T network system – dealing with V2 experiments and passing Corncrake – Bletchley Park’s codename for this traffic – was also difficult to cover, and although it was double banked at the War Office Y Group station at Beaumanor in Leicestershire and Chicksands in Bedfordshire, required between nine and twelve wireless sets, and the problem of intercepting clean texts on this group was never solved. But Baltic Brown had assumed such importance by the middle of 1944, that experimental, but unsuccessful interception, was made at every available intercept station. Eventually the problem was overcome by sending a group of Chicksands operators to Malmö in neutral Sweden where, as part of the British Consul staff, they successfully intercepted the main group and a previously only suspected medium frequency group.
It was known that the most experienced German radar operators were in the 14th and 15th Companies of the Air Signals Experimental Regiment, and Hut 3 and the Y stations kept a special watch on any movement by these units. It helped that the Germans, when they test-fired the V-weapons, sent the reports between outstations and the base at Peenemünde in a home-made code so simple it could be read on sight. In October 1943 it was discovered that the radar detachments of one regiment – the LN Versuchsregiment – were plotting the trial flights of a new missile in a simple substitution code on the same frequencies as Brown Enigma. Then two W/T networks were discovered operating exclusively on secret weapons. The first was a radar-plotting network service based at Peenemünde, discovered because a special piece of radar equipment known as a Würzburg D had been sent to the LN Versuchsregiment at Peenemünde.
The second were the radar plotting stations themselves. This second network was a link between Peenemünde, the practice ground in Poland and an administrative HQ. After Peenemünde was bombed, a training station to practise firing the rockets was set up at an SS camp, Heidelager, at Blizna in Poland. This location was found once the names of the principal Commands involved in rocket production were known. When the rockets went operational a new group of W/T stations were found, codenamed Vera. This traffic accompanied the firing of rockets and summarised it at the end of the day. Moreover, much of the early and detailed information on the V-weapons were found through decrypts from Japanese diplomatic – mainly naval attaché – traffic.
Prisoner-of-war interrogations and MI6 reports were also adding to the picture. Churchill became involved and, as a result, a special investigation was ordered, of which the chairman was Duncan Sandys, Joint Parliamentary Secretary to the Ministry of Supply, and which went under the codename Bodyline. In November 1943 it was renamed Crossbow, with responsibility being transferred from the Sandys Committee to the Air Ministry. On the night of 17–18 August 1943, an RAF raid on Peenemünde, called Operation Hydra, caused severe damage, aided by a diversionary raid on Berlin, codename Operation Whitebait. Professor Jones, commenting on the information on which this raid had been carried out, said: ‘there had been almost no contribution from Ultra’. But he made clear the importance of Ultra when he added:
I always looked at such actions from this standpoint because, vital though Enigma was, it could at any time have been cut off, and if we had become too dependant on it, we should have been at an enormous disadvantaged.
A different view of that day – seen at ground level – comes from artillery specialist General Walter Dornberger, then Director of the Peenemünde establishment, who had been involved in rocket experiments since 1932. He recalled that he had received a warning from the Air Ministry a few days before that we were likely to be raided. At least one copy of all production schemes, drawings and files had been lodged elsewhere and dispersal of the different departments was under way. In addition, all possible air raid precautions had been taken.
The raid must have been a terrific one. Our carefully laid scheme, covering all eventualities and several times rehearsed, had failed completely.
However, Enigma did provide Professor Jones with vital information when a decrypt revealed a Luftwaffe instruction to personnel at research and experimental stations addressed to establishments in what appeared to be an order of precedence, starting with Rechlin, the roughly German equivalent of the Royal Aircraft Establishment at Farnborough. Peenemünde was second on the list, ahead of several other establishments already known to British Intelligence. Jones said this Enigma information enabled him to provide independent evidence of the importance of Peenemünde. The 8th USAAF also carried out raids against the site in July and August 1944. Another decrypt alsoproved useful when, in September 1944, a message was intercepted which asked for Flak ground protection for ‘Flak Zielgerät 76’ and referred to the capture of an enemy agent, adding that the Allies were aware that the weapon would shortly be operational and planned to attack sites before this happened.
Following these attacks on Peenemünde, the Germans subsequently moved much of the work to an underground Volkswagen factory near Nordhausen in the Harz Mountains, to Traunsee, near Salzburg in Austria, and to Blizna, near Debica, in Poland. Other subsequent large sites included Watten, Wizernes, Siracourt and Lottinghem in northern France and Sottevast and Martinvast in the Cherbourg region of Normandy. Another northern French site was at Mimoyecques, but it was the V3 being produced here, known as the Hochdruckpumpe or HDP (high pressure pump), which was a supergun. Further information was obtained by the codebreakers when decrypts of the reports to Tokyo by the Japanese Ambassador in Berlin at the end of September referred to long-range weapons.
Bletchley Park, as part of their role in looking out for these weapons, had been keeping track of the 14th and 15th Companies of the Luftwaffe Signals Experiment Regiment, which had come to the attention of the codebreakers early in the war because of their involvement in the development of navigational beams which guided bombers to their target during the Battle of Britain. Professor Jones had surmised that the Germans would track the experimental flights using radar, and that these two companies would probably be involved. He told Professor Frederick Norman at Bletchley Park’s Hut 3 – which handled German Army and Air traffic – of his thoughts, and asked him to see that Bletchley Park and the intercept service followed these two companies as closely as possible. Above all, he wanted to know whether one or the other of them moved up to the Baltic coast and showed signs of deploying itself from Peenemünde eastwards. 14th Company did, indeed, turn up in the Baltic, and by the end of November it had been established from the decrypts from this Company that the speed of the missile was between 216mph and 300mph, and once 420mph, that the rate of its fall was 2,000 metres in forty seconds, indicating that the missile had wings, and the maximum range might be 120 miles.
A key Luftwaffe decrypt, read in December 1943, sent to the Signals Experimental Regiment was the first Sigint reference to A4 – the German name for the V2. Intelligence sources interpreted this decrypt as meaning that a high altitude rocket was being developed on the Baltic. By this time intelligence was clear that both a pilotless aircraft and a long-range rocket were being developed, enabling counter-measures to be considered, with the V1 the most likely early problem, some eighty-seven ski sites for their launch having been identified by PR flights. Many of these sites were subsequently bombed, beginning in December 1943, and by June 1944 it was thought only twenty-five sites were capable of operational activity. It was known that the flying bombs were being fired by Flak Regiment 155 
