British intelligence on Operation Sealion..

Hey all.. just a question... prior to the luftwaffe attack on Great Britain, did the British know about the operation sealion and how they planned to invade Britain beforehand? how did they manage to find out? If they didnt know before hand, when did they eventually find out ? thanks

 

Theres probablly experts on this, but off the top of my head:

ULTRA or the interception of Enigma radio messages. The Brits were just getting a grip on using this critical source. There were in no way decrypting/reading messages in real time. They were attempting to identify which out of hundreds of daily radio messages intercepted, came from the important HQ and focus on decypting them first. Many critical messages were missed and not read until weeks or months. A few were caught in time to indicate some sort of attack was in preperation, but very few details.

Low level radio traffic from regiments and battalions that did not have the Enigma machine was also intercepted. The codes used for this were easier to break and hints collect from these.

Spys. The intel effort was in chaos as you might expect so close to the Battle of France and the many changes in France. Some anti German Frenchmen were trying to send information to Britian, and a little usefull information got through.

Air Reconissance. The Brits sent as many air reconissance flights as posiible over France. Aside from looking at the ports they wanted to know what the Germans were up to on the French airfields, and what kind of traffic there was on the railroad. Moving cargo barges from Holand & the Antwerp area south to the Channel ports was a obvious indicator. Large groups of infantry camped near the ports suggested the same. Some of the air recon may have observed the rehersals and training exercises. I'm unsure if any actually were seen or photographed, but that would be a clear indication.

The Royal Navy sent patrols close in to supplement the air reconissance.

 

Hitler's war Directive # 16, detailing proposals for 'Sealion', was published on 16th July, 1940 and it is reasonable to assume that information reached Britain shortly afterwards.

 

Britian didnt really understand engima till 1944 i bieleve. Sealion was 42 so i think they probabvly didnt know bu they knew something was coming soon or later.

 

The British were decrypting quite a bit of the Enigma traffic before 1944. The Battle of the Atlantic is a good example.

"Forewarned by Bletchley Park Dowding, with a force of 300 fighters, was able to destroy 187 German planes and to break the offensive. Two days later, on the 17th of September 1940, Bletchley Park decrypted Hitler's order to abandon operation "Sea Lion" and to end the Battle of Britain. Throughout the whole period of the Battle of Britain both Churchill and Dowding had detailed advance knowledge of German battle orders."

The Polish WW2 success in breaking the code of the German Enigma machine

 

Dowding wasn't cleared for Enigma messages until late October 1940, as the day fighting was drawing to a close.

There's no evidence that he had any advance warning of changes during the BoB. As an example, the largest change in conduct of the battle was the Luftwaffe switch to attacking London. That happened on the 7th September. The same day Dowding and Park, the commander of 11 Group, were at a scheduled conference discussing how to meet continued German attacks on airfields. The battle was run that day by Park's deputy, and the change in tactics caught the RAF so much by surprise that the Luftwaffe had almost a free run on London, as the fighter squadrons were protecting the airfields.

 

Thats correct. Dowding's headquarters among others were kept informed of anything important or of immediate operational value without knowing its origin..

 

Another example of how careful one has to be with sources from Poland.....in fact, sixty German aircraft were destroyed on September 15th, 1940.

 

Ronald Lewin, in 'Ultra Goes To War' ( Hutchinson, 1978 ) devotes several interesting pages to a discussion of Ultra and Sealion.

Two key comments which he makes are 'Claims for ULTRA must not be pitched too high' ( p.93 ) and 'All intelligence work involves assembling a mosaic whose key pieces are missing while others are broken or defaced. So it was over Sealion'( p.91 ).

He goes on to say that the key element which resulted in Sealion being taken seriously by the British was RAF photo-reconnaissance showing the high build-up of light shipping and invasion barges in the Channel Ports.

 

It would have been quite difficult for the British intelligence services to have the details on Operation Sealion before the Battle Of Britain, for the simple reason the Germans didn't have the details either.
At the start of the BOB, the Heer and the Kriegsmarine were still attempting to reach some sort of agreement on both the size of the force that could be landed and the actual landing area's, it wasn't until mid-August that these issues had been settled ( though by this time both the Heer and Kriegsmarine had come to the conclusion that any invasion was unlikely to succeed against determined British resistance in the beach head area)

 

thanks for all the info, really helped a lot.