On 21 August, the Chief medical Officer of Fliegerkorps V notified I., II. and III./JG 2, that all flying personnel should immediately be issued with emergency rations in case they had to ditch. These were to be carried in a pocket of their flight overalls and should include: eight Pervitin (methamphetamine) tablets; a handful of coffee beans; a roll of peppermint in a special protective container; and a box of Scho-ka-kola (dark chocolate with caffeine and kola nuts). At the other end of the dietary scale, on the 29th the Luftwaffe announced the distribution of 2,500,000 bottles of champagne, the bulk of them going to Luftflotten 1, 2,3, 4 and 5. If this suggests there was no shortage of luxuries, the basics were scarcer for on the same day Luftgaukdo. Westfrankreich ordered its Aerodrome Regional Commands to report the names of airfields where there was any difficulty in providing aircrew with special meals, especially fresh milk, before take-off or where fresh milk was not available for personnel handling chemicals.

Aerodrome Regional Commands and depots in Western France were told on 1 September to report within the week whether they had an assured supply of potatoes for the immediate future. Not everything sent via an Enigma machine necessarily merited such security, for example the message of 5 September saying that one Flak unit had lent another two cooking pots, one large and one small. Of more significance was a directive three days later, over the signatures of Ob. West and Air Officer Commanding Luftflotte 3 that to ensure “the greatest possible efficiency for the Air Force personnel who are bearing the brunt of the present battle” the fresh meat ration of flying units in Western France was being increased from 200 to 250 grams, the evening meal would rise by 50% and isssues of tinned meat for the midday meal would continue. Providing fresh meat was an Army responsibility and individual units were currently prohibited from slaughtering livestock, but if the Army could not meet the new scales, flying formations were permitted to purchase meat on the open market or obtain it by slaughter.

Compared to what would come later, 1940 saw only the smallest amount of intelligence derived from ULTRA about German naval activity and what there was seems to have come from Luftwaffe sources. On 28 August Fliegerkorps IV forbade attacks on submarines south of 46º N because Italian U-boats were expected in Bordeaux. On 1 September the warning was reiterated, saying there should therefore be no attacks around the mouth of the Gironde. Also that day, Fliegerkorps I announced that during the coming night, a major formation of friendly warships would be be in area between Dutch and English coasts, putting into Dutch harbours early next morning. At noon on 5 September, KG 54 and JG 2 were advised that seven minesweepers and two submarine chasers had left Cherbourg for Brest earlier that morning. Fliegerdivision 9 informed 3.(F)/122 that four or five Schnellboote would be operating toward Great Yarmouth “outside ‘Area Blue’” in the 24 hours from 0600 on the 6th.

Preparations for an invasion of Britain were taking place in plain sight, it did not take ULTRA to reveal the hundreds of barges massing in the Channel ports from early September. The British armed forces had issued the codeword “Cromwell” (“invasion imminent”) on the evening of 7 September, seeing the bombing of London as the precursor to a seaborne assault. Next day the British Ambassador in Madrid passed on the first news that the planned operation was known as »Seelöwe« (Sea Lion). Decrypts bearing on the operation had first appeared late in August but were straws in the wind rather than unequivocal information. All seem to have originated from Luftwaffe sources but since these often entailed discussion with the Army and Navy, the insights gained were not confined to air operations.

On 20 August information was received about a course at Carteret on the west side of the Cherbourg Peninsula. Subsequent intercepts showed this to involve I. Flak Korps, tugs, ferries and firing at sea targets. Trials were intended of a Herbert Ferry (a forerunner of the better known Siebel Ferry) and army engineers were urged to expedite construction of four Herbert and four “wine barrel” ferries but Pionier Bataillon 47 answered that a shortage of wood and screws meant that it could not oblige. The British recognised these trial embarkations of Flak guns as an invasion preparation. In mid-September a request was put in for three 8.8. cm and two 2 cm guns, to spare a Flak unit in Antwerp “the need to make long marches in its loading experiments with seven Siebel ferries”. At the same time “an important party of Flak trainees” was to be transferred to Fécamp and the ferries were to be brought to the sea shore where tugs would come for them. However, I. Flak Korps had “given up the idea of experiments at movement with tanks”.

It was only with hindsight that this message read on 29 August was interpreted as possibly related to an invasion:

There is an S-Kommando (sic) at ANTWERPEN. Fliegerdivision 7 repeat 7 appears to have some connection with it, and also, probably, with Luftflotte 2.

Taken with later messages the “S” could be seen as a possible abbreviation for »Seelöwe« while 7. Fliegerdiv. was already known to be employed for airborne operations.

On 1 September orders were issued to move seven Stuka Gruppen to airfields in the Pas de Calais region, none of them more than 60 km inland (see “Infrastructure” above). On the 15th orders went out that VIII. Fliegerkorps was to transfer its staff “with utmost speed” to Luftflotte 2’s area. The Korps’ targets were to be the cross-Channel guns in Kent, and pending its arrival II. Fl.Kps. would begin attacking with Stuka Geschwader 1. A list of targets would be drawn up in consultation with 16. Armee. The previously mentioned development of airfields and associated rail sidings and facilities for the transhipment of supplies in Northern France and Belgium area for transport units were also interpreted as invasion preparations.

If the invasion threat was seen to have receded in the second half of September—with daylight raids gradually diminishing and the weather worsening—ULTRA intelligence on the detail of preparations increased through into October.