Germany and the German Air Force
Not to be Taken into the Air—I
What German Intelligence learned from Allied Aircrew Documents
Examination of members of the staff of Dulag Luft has made it possible for the first time to appreciate to what extent the Germans were able to extract intelligence from documents and papers carried by Allied aircrew captured in operations over Germany and German-held territory.
Speaking generally, P/W expressed the opinion that it was not the security principles or the instructions issued to aircrew that were responsible for the wealth of documentary information that fell into the hands of Dulag Luft, but rather failure of aircrew to execute the security instructions received. Over and over again notebooks, diaries, letters and scraps of paper were found in the possession of captured crews or recovered from crashed aircraft. Though it is difficult to assess the value of the information thus conveyed gratis to the enemy, that value was undoubtedly very high. Some idea of the type and intelligence value of the information extracted by Dulag Luft from documents that should not have been carried can be gleaned from the examples cited in the first part of the present article. The conclusion to be drawn is that aircrews were insufficiently aware of the intimate relation existing between interpretation of documents and interrogation. In numberless cases the essential clues or reference points were furnished to the interrogators at Dulag Luft by the Documents Section only because a member of an aircrew had not emptied his pockets before an operation. It is perhaps worth emphasising that the ordeal of interrogation would have been vastly lightened in many cases if the instructions not to carry private papers had been scrupulously observed.
According to P/W, useful documents and notes were carried with particular frequency by members of aircrews with little operational experience; he ascribes this fact as not necessarily due to deficiency in security but rather to the beginner’s anxiety to refer to the notes he had made during his training and to a mistrust of his memory.
DOCUMENT INTERPRETATION METHODS
The general object pursued in the interpretation of documents at Dulag Luft was to furnish the interrogators with the maximum amount of information before interrogation commenced. In this way interrogators often succeeded in impressing P/W with their knowledge to such an extent that the latter would talk freely.
The work of evaluation of documents was mainly concentrated on the following points:—
(a) Determination of P/W’s unit.
(b) Target, mission and incidents during the flight.
(c) New equipment and new methods of attack.
(d) Losses and replacements.
(f) Ferrying flights to Europe and Africa.
The attention paid by the document evaluators to each of these points and the methods they pursued are given in some detail below:—
DETERMINATION OF UNIT
Determination of the unit was a matter of primary importance in the work of the Documents Section, for once the unit of a P/W had been established, it was usually possible for the section concerned with unit history to furnish an abundance of facts which, when communicated to P/W, would tend to loosen his tongue.
The following is a description of the various clues pursued in the endeavour by the documents evaluation section to establish a P/W’s unit.
Squadron Markings and Registration Numbers on Aircraft. These were systematically registered in a list which was scrupulously kept up to date. The list was most complete in the case of R.A.F. Bomber Command units, less complete for Coastal and Fighter Command units. The registration numbers on the tails of aircraft were also listed. The squadron concerned in the attack on the Mohne Dam was, according to P/W, established from the registration number of one of the participating aircraft which crashed.
R.A.F. Identity Cards. The old 1250’s were extremely useful because they recorded a history of the various units to which bearers had been posted. Even when these unit descriptions were blacked out at a later period, it was still sometimes possible to read the entries. The pink 1250’s which were introduced shortly before D-Day caused the documents section a considerable headache at first, but even so the serial numbers, the numbers on the rubber stamps and the signatures were found useful. After the documents section had revised its system it was often able to determine a P/W’s unit or, at least, his Conversion Unit from the pink 1250 and to identify flight mechanics as such.
U.S.A.A.F. Identity Cards. In the majority of cases, the original U.S.A.A.F. identity cards, particularly those issued to officers, bore the name of the school at which commissioning had taken place, and thus furnished a clue to function in the aircraft. The new identity cards were considerably less informative but still gave some indication of the station in the U.S.A. at which operational training had taken place or of the date on which the bearer had been staged to the theatre of operations.
Photographs. The photographs on escape passports carried by U.S.A.A.F. aircrew shot down over Europe also helped to identify the unit. Photographs issued by the U.S. 91st Heavy Bomber Group, for instance, were at first recognisable by the fact that all the enlisted men and N.C.O.’s wore cotton shirts, and all the officers O.D. Shirts. Later, all the passport photographs of this unit were finished in an easily recognisable brown tone, which was peculiar to this unit. Photographs of the 95th Heavy Bomber Group originally showed aircrew wearing a suit of uniform pattern, and had a dull grey background; later, however, suits with a striking check pattern and ties of elaborate design were worn. Photographs of the 100th Heavy Bomber Group were characterised by their small and distinctive shape. The 381st Heavy Bomber Group at first photographed its aircrew dressed in light coloured shirts, and wearing a simple dark tie. Aircrew of the 305th Heavy Bomber Group at first carried photographs exactly as they had been issued by the Group Intelligence Officer. It could be observed that aircrew had hurriedly put on a civilian shirt and a civilian coat merely for the purpose of being photographed, and the naked thigh was frequently visible. Members of the 94th Heavy Bomber Group were easily identified by the dark finish of their photographs, by an inscription on the upper margin and by the patterns of their ties.
The photographs of the 303rd Bomber Group could be recognised by a beige strip on which the bearer’s name was written, and which was pasted on to the bottom of the envelope. Another Group, again, could be recognised by the reddish-violet colour of the cellophane envelope containing the photograph.
British escape passport photographs were less informative, as they were issued by operational units at the beginning of the war only. Those encountered later had usually been taken at an O.T.U. or Conversion Unit, but even this gave a clue to the bearer’s training and, in the case of the C.U., to the Bomber Group to which the bearer belonged.
A few units, including No. 103 R.A.F. Squadron at Elsham Wolds, could be readily identified by the typical lettering on the escape kits, although the inscription made no mention of the actual unit.
U.S.A.A.F. Ration Cards. The ration cards carried by U.S. aircrews were so useful for purposes of unit identification and history that a separate card-index was kept for them. British ration cards were much less useful, and information obtained from them was not separately card-indexed. When the U.S.A.A.F. first came to Europe each Group issued its own ration cards, but subsequently standard cards were issued to all airmen in the E.T.O. For unit identification purposes, the method of cancellation was found to be very useful. In the case of the U.S. 100th Bomber Group, it was discovered that cancellation was being effected by means of a thick black pencil (and later by coloured pencils), and that the card had been placed on a roughly planed table surface. It was subsequently discovered that it was possible to determine most of the U.S. Heavy Bomber Groups by carefully studying the technique of cancellation.
British Ration Cards. British ration cards were only occasionally informative. Such entries on these cards as “Sergeants’ Mess,” followed by the name of the station, were occasionally found. In some instances a ration card gave evidence of the length of time its owner had spent in his unit and occasionally a transfer could be deduced.
Other sources of information were bicycle or similar licences, bomber code covers, which appeared to have been supplied to stations in numerical sequence, and U.S.A.A.F. start sketches and formation charts. Bomb loading tickets, both U.S. and British, gave, in addition to the valuable information concerning the bomb load, type and distribution of bombs, fuses, etc., as well as an indication of the unit. P/W also mentioned that laundry marks on underclothing and handkerchiefs very frequently supplied a clue to the unit of a captured crew.
Target, Mission and Incidents during the Flight
Information bearing on target and mission was usually found in the captured logbooks of British crews, or in the case of certain U.S. units, in operational orders issued to pilots and bombardiers. Handwritten notes made by British crews during briefing were frequently captured, and though these were often extremely difficult to decipher, they were frequently very informative.
An excellent example of the value of such notes occurred after the R.A.F. raid on Leipzig on the night of the 20th October, 1943, when a small, dirty and oil-stained piece of paper was discovered in an aircraft shot down in the course of the raid. Some notes scribbled on this piece of paper gave in a few significant words the entire plan of attack, the bomb load, the methods of target marking employed, the turning points on the route of approach and instructions on the release of “Window.”
The “Captain of Aircraft Maps” issued by the R.A.F., always gave a clear picture of the plan of attack, particularly when pilots added notes of their own. In many cases information was gleaned from log books or from separate notes on previous missions or planned missions.
It was proved to be possible to forecast targets which the enemy was planning to attack from the captured plans of attacks which had manifestly been cancelled at the eleventh hour, and to inform the appropriate defence units in time for the subsequent attack. As an example of this, P/W stated that captured documents had shown that the first daylight raid on Bruex had been planned for the beginning of April, 1944, but had not then been carried out. Through some error by Dulag Luft in transmitting this information to the authorities at Bruex, the latter were not ready for the attack, which actually took place on or about the 12th May, 1944. In other cases, however, warnings were given in time, particularly after some of the more seriously threatened German industries, including oil refineries, had been put in direct contact with Dulag Luft. It should be added that alternative targets noted in aircraft briefings also served as an indication of future targets, even when not actually attacked on the mission in question.
The German defence forces were very much interested to learn which of the German defences had been recognised, and how they were assessed as targets. On one occasion the German Flak batteries were informed of gaps in the Flak belt, designated by code names and co-ordinates which appeared on some captured maps.
[Source: AIR MINISTRY WEEKLY INTELLIGENCE SUMMARY, No. 301, 9th June 1945.]