German code breaking during WW2, Part Four

The following depicts the sequence of events in a night raid, showing how , in the latter years of the war , it could be identified by SIS, and advance warning given:

17:00 Lancaster units have been alerted for operations during the first half of the night. Whether Halifax squadrons are to be used also is not yet known. 5 Group commands special attention.

18:00 100 Group has already taken off.

18:25 The first aircraft off 100 Group have been plotted ; it reported damage. By means of many bearings its course is learned ; it is flying over Dunkirk on a southeast course toward the Charleville area.

18:25 A bomber code message in the new setting which is only valid for one night , is sent by an airfield of 1 Group , this means that the aircraft of 1 Group are already airborne but their course is still unknown.

19:00 The monitoring of Allied aircraft networks , carried out by Meldekopf2 , indicates a large enemy (British) formation in the Somme-Muendung area. At this point an advance warning is broadcast to all parties concerned.

19:10 An OTU aircraft attempts to turn home on an airfield of 5 Group and is turned away by the airfield D/F section (certain “Q” signals). Therefore the participation of 5 Group must be reckoned with. The HF and VHF D/F networks are alerted to monitor the frequencies of 5 Group.

19:20 An aircraft with a known operational call-sign requests a check bearing from the airfield D/F section of the Halifax units. Therefore , the Halifax units also warrant attention.

19:35 The Allied Air Raid Reporting Service reports a second wave of aircraft. It is probable that on this night all groups are taking part in the raid.

19:45 The first line bearing on a “Magic Box” (H2S) is reported. Since radar intercept is now bringing results , the course of the enemy units can now be checked depending on the number of bearings. Once the course is accurately determined , night fighters can be brought into play.

19:50 A “Magic Box” is plotted over the Deutsche Bucht. Since no jamming aircraft fly into this area it can only be a Mosquito flight or a mine laying aircraft.

20:00 The control stations of 4 and 6 Groups transmit “winds aloft” messages on a CQ call-up. From this it is known that the first wave consists of Halifax squadrons of 4 and 6 Groups led by pathfinders of 8 Group. The bomb-release signal can be expected within 20-30 minutes of the “winds aloft” messages and therefore the formation will probably not intrude deep into Germany proper. Attention must now be given to the Boomerang-controlled Mosquitos of 100 Group.

20:10 The first wave is plotted by radar intercept ; course is toward the Rhine-Westphalia industrial district. The second wave is plotted for the first time in the Rheims area.

20:20 A “winds aloft” message is heard on the 1 Group frequency ; this time it is sent by the aircraft to the control station. 1 Group therefore has penetrated deeper than the Halifax formation. This information allows identification to be given to previous “Magic Box” plots on this unit.
Note: 100 Group usually flies in a wide formation , veiling the movements of other groups and making it difficult to determine the course of individual units.

20:25 The identification of all jamming aircraft which have been plotted is successfully completed and their relative positions with respect to the individual units clarified.Points of concentration of the jamming aircraft can now be reported.

20:30 Zero beat tuning on the headquarters of 5 Group is heard. Accordingly , fresh warning is given of activity on the part of this dangerous group whose course is still unknown.

20:35 The Boomerang controlled target markers for the Halifax formation are plotted. Special local warning is given to the area in which the attack is expected.

20:37 Interception of pathfinder R/T traffic (VHF) on the “C” frequency of 8 Group ; the aircraft are identified as Boomerang controlled Mosquitos. A report to ZAF states : Halifax formations will release bombs in a few minutes.

20:39 “Winds aloft” messages are now sent by pathfinders of 8 group also. The contents are identical with those sent by 1 Group. To what extent 8 Group is a part of the main bomber stream is , for the present , still not clear. The report on the strength of the intruding formations states :

aa) Halifax formation approximately 380-450 aircraft (Lancasters of 6 Group have probably not accompanied them) , led by Mosquitos.

bb) Lancaster formation heading toward southwestern Germany with about 300 aircraft (to what extent 8 Group , except for its pathfinders , is represented in the formation remains uncertain).

cc) 5 group is active in undetermined strength ; area of operations for the present unknown.

dd) Mosquito formation of 60-80 aircraft toward Berlin (target is only presumed since Mosquitos regularly attack Berlin at this time of night).

20:40 3 Group will probably not operate since training activity is taking place on their airfields.

20:50 A small amount of training flight activity begins on two airfields of 5 Group. It is therefore presumed that specialised squadrons are carrying out a special mission.

20:55 OTU aircraft of 93 Group are recalled to their bases. Consequently there is probably a bad weather front moving toward their airfields. The W/T companies are instructed to pay special attention to rerouting orders from the control stations of this group.

21:15 The control station of 8 Group sends a CQ message giving a report of winds aloft over the target. This indicates that the Lancaster formation will drop its bombs within the next half hour. The target area can then be determined by computing the distance that the Lancasters fly in the next half hour (their course being already known) and advance warning given.

21:35 The control station of 5 Group resumes its zero beat tuning. It might be for D/F purposes and 5 Group might be in the vicinity of the target.

21:40 Report from Jagddivision 7 target markers over the city X.

21:40 Aircraft of 1 Group send “winds aloft” messages for a section already flown through (for return flight purposes). The result is an SIS message stating : Lancaster formation has reached the target ; no further penetration to the east.

21:45 The control station of 3 Group sends an order to a squadron from Waterbeach diverting it to another airfield. Either the bad weather front has already reached the 3 Group bases or Waterbeach must be kept open for aircraft returning from operations.

21:45 W/T pathfinder traffic from the control station of 5 Group is intercepted. Accordingly , the special squadrons of the Group are in an area directly in front of the target. At the Meldekopf great excitement prevails ; where are the aircraft ? The possibility that they are over Germany is slight because no flights were reported which were not identified by SIS. After much telephoning to various tactical headquarters it is finally learned that a rather small bomber formation is approaching Bergen. Immediately an identification is made ; these are the special squadrons of 5 Group. The first plot on a “master of ceremonies” of 5 Group confirms this assumption ; the special squadron is flying over southern Norway.

21:50 An aircraft of 8 Bomber Group sends the first report of results ; it is plotted on its return flight from the area of city X in southwestern Germany. The return flight of the main bomber stream has therefore begun.

21:50 The Halifax airfields begins sending reports of weather over the base. Landing conditions seem to be favourable in their area.

21:53 The first report of results is intercepted on the Coningsby airfield frequency ; it is immediately repeated on the Group frequency.
Note: The pathfinder traffic of this group was especially interesting. The “masters of ceremonies” for the most part did not avail themselves of the three letter code and used plain text. 5 Bomber Group which in other matters was generally acknowledged to be a well trained unit , often employed new types radio procedure carelessly. The introduction of “winds aloft” messages in December 1943 can be cited as an example. Instead of using the well compiled code provided , messages were sent practically unencoded , or at least those parts were left unencoded which were most important to SIS. After several aircraft had measured the velocity of winds aloft on a certain section of the route and passed this information on to their airfield , the headquarters then computed the probably wind velocity for that section of the route still to be flown and transmitted this intelligence to its aircraft in flight. Since the code letters used for this purpose were easily broken , the headquarters actually revealed the intended depth of penetration of its bombers and gave SIS an opportunity to determine the target in advance , to inform the Command between which degrees of longitude the bombers would change course , when they would drop their bombs , how many main waves there would be etc. It was especially easy in the case of 6 Group to determine its division into various waves because the Group headquarters sent a “winds aloft+ message to each separate wave. The pathfinders of 5 Group also used plain language when W/T traffic was introduced ; only later did this go over to the use of a special three letter code which changed daily.

21:55 A bomber code message from the headquarters of 1 Group is deciphered and is found to contain re-routing instructions.
Note: Several times it happened that the bombers were called back by their control stations shortly after passing over the English coast. In such a case certain aircraft receipted for the message. It ws not determined to what extent the British had to authenticate unusual messages. Under certain circumstances the Luftwaffe SIS might have been able to send decoy orders to the bomber groups. However , such an attempt was forbidden by the Chi-Stelle (Luftwaffe SigInt Head Office) because it was afraid , by such a practice , of causing all bomber command W/T traffic to dry up.

Whatever further traffic was intercepted from the bomber formations on their outward flight could no longer be used tactically.

By far the greater part of the effort was consciously directed to producing possibilities for early warning from the traffic of RAF Bomber Command.

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