Bletchley Park first broke regularly into German machine ciphers in 1940 but the intelligence yield was still limited in a number of ways.
Only a few Enigma keys, notably the Luftwaffe’s “Red” (as BP named it), were being broken; there were few staff and the first machine-aids were only just arriving. Decrypts following the armistice in France revealed the progressive installation of landlines to German units in their new quarters and bases, placing communications beyond BP’s reach. The British not only lacked their later capacity for decryption and analysis, they had yet to develop the background knowledge of the Luftwaffe and its personalities that would enable them to exploit the decrypts to the full.
During the Battle of Britain there seem to have been relatively few notifications of specific attacks, whether deciphered before or after the event. “Operation ADLER” was something of an exception perhaps because it represented a significant departure from German operations to date. It is perhaps a sign of the RAF’s effectiveness over the Pas-de-Calais that Luftwaffe commanders had wanted to bomb its infrastructure even before the Dunkirk evacuation had got underway. After deciphering a message sent at 21.00 GMT that day, the British read how:
Allied fighter aircraft carried out attacks along the coast on 23 May. In the evening, Luftflotte 3 asked for formations of He 111 to attack ground organisations in South East England in order to knock out the British air force.
From a signal issued at 13.07 hrs. on 24 May it was learned that:
An air attack on English aerodromes was planned for [that day], but had to be postponed on account of unfavourable weather conditions.
On 6 June, 11 of I./KG 27’s He 111 took off frm 2000–2220 GMT to attack English aerodromes. However, on 14 July, Luftlotte 3 issued an appreciation, deciphered as follows:
Experience of last few days on the south coast of England when attacking convoys, has elicited strong AA and fighter defence, and very accurate (interference?) with [Note: “interception of”, perhaps?] German aircraft up to 25 km. out to sea. This has made attacks much more difficult. Mining along the English south coast from close inshore up to 25 km. seawards … is requested. This mining is intended to drive convoys more out to sea, and the Germans thus hope for greater success with less loss to themselves.
Perhaps with these lessons in mind, OKW and the RLM had the same day directed Luftflotten 2, 3 and 5 that:
(1) Attacks on England by day are only to be made when weather offers adequate protection against fighter-attack. These raids must be made by single aircraft only. Pilots must be expressly ordered to break off attack whenever weather no longer ensures surprise.
(2) Attacks on convoys on the other hand are to be made in such strength that annihilation of the convoy can be counted on. Attention is again called to necessity for adequate fighter and heavy-fighter protection.
Sometime between 15.40 on 10 August and 11.30 the following morning, BP deciphered an order which Luftlotte 2 had issued on the 9th at 09.00 hours:
Prepare ROSENGARTEN [Rose Garden]. ADLER [Eagle] probably … on the afternoon of 9 August. Definitive order with exact time will follow.
Whatever ROSENGARTEN was, within nine hours it had been postponed and all preparatory measures cancelled.
Traffic deciphered on the 10th included several signs that trouble was brewing. An instruction was given at 09.00 that day by Naval Command Channel Coast to a Harbour Commandant (Hafenkapitšn) to ready all boats suitable for sea-rescue work; orders to put to sea were to be given later.
Another sign that the Luftwaffe would soon be operating intensively over Britain came in these instructions of 10 August:
Aircraft crews are always to wear uniform on such flights. On the left sleeve of their special flying clothes they must wear their badge of rank; when they make forced landings, if they cannot get away, they are to open the collars of their special clothes so as to make the uniform visible and to prevent suspicion of espionage.
The English Government has recognised that German aircraft crews will be conforming to International Law if they wear uniform, and the German Foreign Office has pointed out in a note to the International Committee of the Red Cross that crews wear uniform under the flying clothes that are customarily worn by flyers of all nations and that parachute troops do the same. The commands of all units are responsible for seeing that the wearing is strictly adhered to.
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The sources for this article is the deciphered German signals held at the National Archives, Kew, London in file HW5/4.
I think that all times are GMT but it was some while before this began to be stated at the head of very report.
Article © Nick Beale 2012