Kampfgeschwader 54 received an order forbidding any aircraft to fly to the aerodromes of Alderney, Jersey and Guernsey, other than those moved there “for the bombing operation.” Although not read by BP before Adlertag, another message from KG 54 gives the sense that they were building up to something. On 11 August a day-old signal was deciphered in which the Geschwader indented for 166 explosive charges and detonators for destroying aircraft which came down in enemy territory. On 12 August the Ergänzungsstaffel was asked to send on as soon as possible any Ju 88s that were ready for action; crews with preliminary dive training should also come to operational bases where they could complete their bomb-dropping training.
By mid-afternoon on 10 August, the British knew that, at 01.30, Fliegerkorps 5 had ordered I./KG 51 to be at readiness state 2 from 07.00 and that KG 54, ZG 2 and JG 2 would be subordinated to VIII. Fliegerkorps “for a special operation.” On the 11th, the I. Fliegerkorps’ order of the day advised that “circumstances” could necessitate attacks by KG 1 and KG 76 on targets other than those they had been briefed for. Accordingly, they should familiarise themselves with targets Nos. 1017, 10118, 10281, 1099 and 10136.
A further straw in the wind was II./JG 2's indent for 80 »Flugzeugvernichtungsmittel« — charges to destroy aircraft down in hostile territory.
A flurry of intelligence came in between 18.45 and midnight on 12 August. The first decrypt to be teleprinted to British commanders was a signal from Luftflotte 2’s Operations Officer, originating at 13.30 that afternoon:
Lfd. Nr. 2180/40: Geheime Kommandosache
ADLER, probably FREIBURG, BRUSSELS, KARLSRUHE, HAMBURG, DARMSTADT, LEIPZIG: final decision follows by telephone.
Bletchley’s analysts could only offer the conjecture that this related to “an important operational matter” and was a string of code-names (the overnight shift would add that they “may well be pseudonyms”; by October several Luftwaffe direction finding stations named after German cities were known). The document’s intended recipients were not known either although it was thought that I. Fliegerkorps might be amongst them.
Later that evening confirmation was received that ADLER would go ahead on the 13th and that the five code-names, now thought to represent places, would be involved. The V. Fliegerkorps duly forwarded the information to the units under its command. A subsequent message from the same Korps’ Operations Section (and no more intelligible) read:
Secret: ADLER, TANNENBAUM [= pinetree], ZAUNKÖNIG [= wren], HECKENROSE [= dog rose], FRANKFURT, LEIERKASTEN [= barrel-organ], BACHSTELZE [=water-wagtail], REGATTA, WEINESSIG [= wine vinegar].
A weather report originating at 14.00 hours advised all units on V. Fliegerkorps’ radio net of perfect flying weather “in the whole area.” A follow-up forecast two hours later, was seen by the British, albeit tentatively, as “additional evidence that some large scale operation is proposed” and that view probably crystallised when they read these tactical instructions for missions over England:
The assembling of bomber, fighter and heavy fighter units for attacks should so far as possible not take place over the coast, because the special enemy wireless stations (De Te Apparatus (sic)) [= Dezimeter Telegraphie Gerät = radar] will already be in action and reporting the assembly of the units, which gives the enemy fighters an undesirable advantage.
However the assembly of light fighters far inland is impossible because of their short flying range and every effort must therefore be made that bombing units shall fly over the jumping-off grounds of the fighters at the height and on the course on which they are going to attack.
The fighters are only to start as the bombers fly over and while gaining altitude are to join the bombers as they proceed in the direction of the attack.
The danger however must be guarded against that where visibility is bad the fighters will not see the bombers flying over in time and will start too late.
It will therefore be better in the case of bad visibility for the heavy fighters that are situated further inland to make an arrangement with the bombers for providing immediate protection while it is preferable for the light fighters to work in close formations and to be ordered into the target area on a time schedule.
In order to avoid heavy losses it is essential that all units fly together in close formations.
Moreover after the attack all units including Ju 88s, must close up again, as aircraft flying alone will inevitably become victims of enemy fighters.
It must be impressed on all units that closest formation flying is essential.
The signal intercepted went from V. Fliegerkorps to KG 54 and JG 2 but the instructions were thought probably to have been issued to all German units operating against Great Britain.
More indications of an impending attack came in between midnight on the 12th and 07.00 next day. A sea-rescue centre (possibly Cherbourg) had ordered Harbour Commandants to place all security vessels in a heightened state of readiness from daybreak. Shortly after that, the Boulogne sea-rescue centre told the Commandants of Dunkirk and Ostend to “begin at 0515 hours.” At the same time as the latter instruction (21.00 on the 12th) a weather forecast went out to the Luftwaffe. Bletchley thought the Germans “apparently considered [it] of special importance.” Covering the Channel and South West England, it predicted:
Area mostly cloudless, ground hazy, good visibility high up, wind at 5,000 metres NW, 40 to 50 km/h.
continued on next page…
PART TWO OF FOUR