Turing Sources

Operation Ruthless, October 1940

Transcription of documents in British National Archives, ADM 223/463

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The documents quoted here are taken from an Admiralty file (ADM 223/463). They illustrate the situation in October 1940 when Turing was unable to make effective use of his methods for deciphering naval Enigma. These methods required (i) enough familiarity with the traffic for cribs to be guessed and (ii) some knowledge of the bigram table used for the indicator system. In 1940 neither of these conditions were fulfilled. They were desperate for a 'pinch' of material.

When this file was released in 1996, it attracted particular attention because a plan for capturing Enigma material from a German naval rescue boat was devised by Commander Ian Fleming, in 1952 the creator of 'James Bond'. Indeed Fleming hoped to execute the plan himself. This plan ('Operation Ruthless') was approved but never put into effect. Enigma material was indeed 'pinched' from the Krebs off Norway in February 1941 and Turing's methods then made a successful start.

For more on the context of these documents, go to this page of the Alan Turing Internet Scrapbook.

This text is © Crown Copyright and is transcribed only for personal and academic research purposes.

The first document quoted is a memorandum dated 20 October 1940 from Frank Birch, head of the naval interpretation section at Bletchley Park, to the Admiralty.

Turing and Twinn came to me like undertakers cheated of a nice corpse two days ago, all in a stew about the cancellation of Operation Ruthless. The burden of their song was the importance of a pinch. Did the authorities realise that, since the Germans did the dirt on their machine on June 1st, there was very little hope, if any, of their deciphering current, or even approximately current, enigma for months and months and months - if ever? Contrariwise, if they got a pinch - even enough to give a clue to one day's material, they could be pretty sure, after an initial delay, of keeping going from day to day from then on; nearly up-to-date if not quite, because the level of traffic now is so much higher and because the machinery has been so much improved. The 'initial delay' would be in proportion to the pinch. If the whole bag of tricks was pinched, there'd be no delay at all. They asked me to add - what is self-evident - that they couldn't guarantee that at some future date, near or remote, the Germans mightn't muck their machine about again and necessitate another pinch. There are alternative operations possible. I put up one suggestion myself, and there are probably lots better. is there anything in the wind? I feel there ought to be.

The second document is the plan for 'Operation Ruthless' as proposed by Fleming to the Director of Naval Intelligence on 12 September 1940.

I suggest we obtain the loot by the following means:

1. Obtain from Air Ministry an air-worthy German bomber.

2. Pick a tough crew of five, including a pilot, W/T operator and word-perfect German speaker. Dress them in German Air Force uniform, add blood and bandages to suit.

3. Crash plane in the Channel after making S.O.S. to rescue service in P/L.

4. Once aboard rescue boat, shoot German crew, dump overboard, bring rescue boat back to English port.

In order to increase the chances of capturing an R. or M. with its richer booty, the crash might be staged in mid-Channel. The Germans would presumably employ one of this type for the longer and more hazardous journey.

Ian Fleming later added other details to the plan:

... N.B. Since attackers will be wearing enemy uniform, they will be liable to be shot as franc-tireurs if captured, and incident might be fruitful field for propaganda. Attackers' story will therefore be "that it was done for a lark by a group of young hot-heads who thought the war was too tame and wanted to have a go at the Germans. They had stolen plane and equipment and had expected to get into trouble when they got back". This will prevent suspicions that party was after more valuable booty than a rescue boat.


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