The South African
Military History Society

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Die Suid-Afrikaanse Krygshistoriese Vereniging

ENIGMA Report Summary

The talk was introduced by an account of the writer’s acquaintance with S Gorley Putt, who at that time was Warden of Harkness House that served the Commonwealth Fund of New York that sent American students to British Universities. During the early part of the war he had been called up to serve in the Royal Navy. He wrote his first book, ‘Men Dressed as Seamen, an account of his life as a conscript on board HMS Tiddley [his pseudonym for HMS Woolston, a WWI destroyer [1917] which was then only capable of convoy escort duty. Gorley’s father was captain of a ship lost at sea during WWI.

The book was published in 1943 after he had joined Naval Intelligence at Bletchley Park in late 1941 and it was illustrated by a naval acquaintance, Roger Furse. It went into four impressions in the same year to much literary acclaim.

In Gorley’s autobiography, Wings of a Man’s Life, published in 1990 and still tied theoretically to the Official Secrets Act [until 1999], although much Enigma information had already been published since 1972, he describes his experiences in the Naval Section at Bletchley Park, but they are mostly limited to a description of the people he was working with; the high pressure and the strain of their occupation – was the information adequate, was it in time, what was the result? To enter the enemy’s mind; to guess probable reactions.

He was ‘elected’ by the academic residents to be billeted at the Duncombe Arms in Great Brickhill, a village a couple of miles away. They were collected for each exhausting one of three 8-hour shift by girls of the Transport Corps. There were mathematicians, classical scholars and linguists, some of them prominent literary figures, then or later, many were from Oxford and Cambridge. Bletchley is roughly half way between the two universities.

There is a list of names of some of the people who worked there; of a few hundred given, one third of them were women; Gorley’s name does not appear, but four of his close colleagues mentioned in his memoirs do.

By 1944 there were 6 000 people working at Bletchley Park, which had started at 30, increased to 1 000 and most dramatically after the Americans arrived when Germany and Japan had declared war. American shipping had been exempt from attack until then.

There were quite a few very eccentric characters amongst the scholars including homosexuals who were a security risk, being open to blackmail.

However, one was a Soviet mole. John Cairncross, one of the Kim Philby’s Cambridge spy ring who had infiltrated Bletchley Park and was passing on Ultra [the information generated by Bletchley Park] to Moscow.

Thomas Nashe, in the ‘Unfortunate Traveller’ of 1594, thinks of such an situation, ‘A man were better be a hangman than an intelligencer and call him a sneaking eavesdropper, a scraping hedge creeper and a piperly [peppery] pick thanke’ [ingrate].

It was essential to guard one’s sources of information; there is ‘no point in reading other people’s letters if they know you are doing so’. These ‘letters’ mentioned by Gorley at that time were confined to those of naval interest.

Within other people’s letters, even when they became readable, there were often embedded obscure secret clues familiar to crossword puzzle users, scholars of Greek or other literature.

Less important signals might yield useful information to be forwarded to the relevant destination.

Naval matters mainly involved Hut 8 - Atlantic, crypto-analytical - Hut 6 Mediterranean and N. Africa - Hut 3 Intelligence.

The chief aim at the time Gorley joined B P was to discover routes and timing of enemy convoys in the Mediterranean supplying German and Italian armies in North Africa.

The Italians used an Enigma machine without a plug board, but relied more on radio signals using cypher and codes that lent them to cribs and rodding. The Italians often sent out dummy radio messages to hide increases in real traffic.

Small coastal craft may not appear important, but what of the Lupo, known to be a small ‘wine carrier’? Where wine goes, Italian troops must be going, so please don’t sink her!

Short wave, high frequency radio signals enabled direction-finding and the sources could then be plotted. Plotting the probable course and probable speed of enemy surface vessels and submarines was his team’s chief occupation; the results were then forwarded to the intelligence analysts of the appropriate department, hopefully to be in time to be of use.

For instance a large cargo ship turned up in the transcript of a convoy list, named Gautier. The name could not be found in Lloyds Shipping List. Gorley, amongst his team of four said, “Try under ‘T’’. Théophile Gautier [the French novelist]; this was a ship whose tonnage and speed was available to help judge the convoy’s further progress.

The discovery of an enemy convoy supplying North Africa might need an aeroplane to go and ‘spot it’ so that the enemy did not think of leaked prior information. It was essential to guard sources of information.

Study of the traffic flow of radio signals in the Eastern Mediterranean helped in the elimination of the Italian Naval resources at the battle of Matapan - another story.

They were too late to advise the Admiralty that the battle cruisers Scharnhorst and Gneisenau had left Brest for Norway, which was a blessing in disguise since they were not located due to changes in departure time and the Allies would not be expected to know that unless the code had been broken.

At a Bletchley Christmas pantomime a line for the role of Hitler, after the battleship Scharnhorst had been sunk, thanks to their naval intelligence, ran ‘Scharnhorst ist nicht so Gneis nau’.

Nashe wrote further in the Unfortunate Traveller, ‘What need the snaile care for eyes when he feels his way with his two horns as well as if he were as sharp sighed as a decipherer’.

The Enigma machine was invented and patented at the end of WWI by Arthur Scherbius who coined the name ENIGMA [to speak darkly].

It was used for commercial and diplomatic traffic in the twenties and thirties being adopted by Nazi Germany as well as being used in Italy and Japan. The Germans added a plug board and later two more wheels increasing the complexity of transcription by the machine.

In December, 1932, Marian Rejewski, Polish mathematician and cryptologist saw flaws in the German cypher procedures of the plug board of Enigma but did not know the wiring in order to create a copy.

Hans-Tilo Schmidt obtained access to German cypher materials, including daily cypher keys and plug-board settings, thanks to his brother being a general in German Intelligence, which he then sold to the French Deuxième Bureau who passed the material to the Poles so that they could then build their own machine, learn the wiring, break and read each coded message – provided they had the latest Enigma settings when they could continue reading German cypher traffic.
Receiving handsome rewards to support his lifestyle, Schmidt kept the French supplied with daily cypher keys and plug board settings which the French continued to forwarded to the Poles. He became their double cross agent over the next 10 years.
[In 1943 he was betrayed to the Gestapo and died in the Berlin Gestapo prison after taking, or being given, cyanide].

The Poles developed a cryptologic ‘bomby’ to search for rotor settings until the Germans added 2 more rotors.

The British had managed to decrypt many Enigma messages, the result known as ‘Ultra’.

By October 1939 the most important Polish cryptographers had escaped to France. The Poles had sent the British and French a model of Enigma.

There was some deciphering success thanks to German procedural flaws, operator mistakes and failure to introduce changes in procedures. Further progress required the capture of key tables and hardware so that

The message receiver could have his machine set the same way as the sender.

A quintillion of possibilities were dependent on wheel positions, plug board connections and the position of the starting wheel.

From the plain text message each letter key is pressed and lights a lamp and turns the wheel to the next letter at the same time. Pressing the same key twice does not produce the same letter due to the rotor moving one place. Each letter of the message is then written down for translation.

A large machine called a ‘bombe’ [after bomby – Polish for ticking] – a huge computer type of machine to discover some of the daily settings of Enigma; it could handle 40,000 messages a day and could reduce the options to a small number of possible solutions that would then be submitted for individual decryption attempts.

The main Sources of current codes and settings were from German shipping until the wheel order was changed again.

The result has then to be translated from German into English and forwarded to the intelligence sections. This could take a few hours. Solving the message without settings, using cribs and the bombe, could take several days.

One thousand ENIGMA machines were eventually used in WWII; later, lighter models had a typewriter attached.

In February 1940 - U 33 was discovered mine-laying in the Forth of Clyde and depth charged to the surface; one Enigma wheel was captured; the rest had been thrown overboard.

In April 1940, a trawler with a false name Polares was captured off the Norwegian coast flying a Dutch flag. A bag was rescued from the sea and later invaluable cypher tables and plug board settings on a scrap of paper were found on board. It was the first time signals could be deciphered – for a short time, but further clues were recognised.

In May 1940, U 43 was off the Suffolk coast and depth charged to the surface, but it was scuttled in shallow water. The Germans tried to bomb it.

The Germans had been able to read the very primitive British Naval messages and sink the aircraft carrier Glorious; also to have knowledge of where the convoys were congregating in the Atlantic thus contributing to the enormous loss of merchant shipping. This was partially due to the capture of the British submarine, HMS Seal> with its papers and mine maps in the Kattegat [between Denmark & Sweden] in May 1940.

A new tactic was developed whereby the German submarine only signalled its position to HQ when a convoy was sighted, instead of a daily broadcast. It then emitted signals every half hour to attract the ‘wolf pack’.

A submarine could travel at 12-17 knots on the surface, only 7-8 knots submerged which was enough to continue with the convoy and select their targets.

The challenge of ‘happening’ to capture a German ship or U boat was recognised; some elaborate ideas were contributed by operators such as Ian Fleming [James Bond], but were over-elaborate and never used. Basically the idea was to capture and control the vessel before the crew could throw machine and codes overboard.

In March, 1941 during a diversionary Commando attack on a Norwegian port the opportunity came to capture the trawler Krebs that was fleeing the scene.

A large force sailed to catch the München NE of Iceland. The current codes and the machine were thrown overboard, but a representative of Bletchley Park who knew what to look for, found code books and had them in the Park 3 days later. Fortunately the radio operator had not finished his ‘captured’ message. The München then had to be taken to Scapa Flow and hidden.

In May, 1941, U110 was shadowing a convoy’s right flank at periscope depth and fired 3 torpedoes the fourth one stuck, but water was automatically pumped into the tube just the same, so that the submarine was suddenly nose heavy, but could not dive soon enough to avoid being depth charged whilst still in shallow water and was obliged to surface.

German submarine tactics at the time were to lie submerged until the convoy had passed abeam and then attack. A new Royal Naval tactic was to have a forward screen of ships in line abeam to detect any waiting submarine, and in this case had been kept on further than usual.

The boarding party had 1½ hours to unscrew the Enigma and gather all the books and papers, expecting it to sink at any time. The submarine was then towed back towards Iceland, but sank on the way due to the damage.

German prisoners were allowed to write to relatives at home. Their code had been broken and it was important that these prisoners from the submarine were allowed to think that the U 110 had been scuttled when writing home.

By June 1941 there was still no permanent solution for the Enigma.

A further capture was needed: it was decided to capture the weather ship Lauerenburg that was about to relieve another ship stationed NE of Iceland with the aim to capture, before it could be scuttled, the current codes as well as those for the following month. A Bletchley Park representative was on board to collect all relevant material which arrived at B P 3 days later.

The U boat Naval Enigma could then be read mostly within minutes for the rest of the war.

After a visit by Churchill to Bletchley Park he gave extreme priority to the staff recruitment needed to minimise delays.

Later in 1941 it was possible to set up ambushes for German submarine supply ships; 8 were sunk, also 7 weather ships. No Allied convoys were intercepted having been rerouted to avoid wolf packs and directed to sail beyond the range of U boats.

The U 570 was spotted by aircraft and was unable to dive. She yielded a referenced grid map of the Atlantic that was brought to Bletchley Park.

The German supply ship Gadania was supposed to be spared, but was captured by accident and had to be towed to Scotland; codes and bigrams were recovered.

Was that being too successful? – Aircraft spotting over the Atlantic was increased to account for it.

In November 1941 shipping losses were now less than 10%

There was a missed opportunity by a British submarine of sinking 3 U boats meeting at Cape Verde – a suspicious coincidence? - dismissed by the Germans.

U 126 was caught being supplied by a ship with a false name. The ship was sunk, but not the submarine. The crews were taken by U boat to another supply ship, the Atlantis that was also sunk; all crews were then brought to Freetown and afterwards to France – a possible source of information from the crew.

On the other hand the sailing of the Tirpitz, although it hit a mine in an area thought to be mine-free, was not put down to prior information of its sailing.

The British destroyer Ashanti flew a German flag while approaching the trawler Geir. The crew were unsuspecting, but started to jump into the sea as guns came round and opened fire; one shell went through radio room, so there was no possibility of a signal of the attack. A rich haul of code books was captured.

Other codes were being used for small ships, dockyards and harbours that provided further clues in deciphering.

The golden period for Bletchley Park came when signals for German surface ships and submarines were read every day, with only occasional blackouts, for the rest of the war. The problem was always to mask the success of Ultra. Still transcription [entry to exit] time could be anything up to 2 days. Continued success was due to capture of more submarines that were forced to the surface.

Many lives were saved in 1942, particularly for the Arctic convoys such as PQ 12 that started off Iceland. Information enabled them to be diverted away from such battleships as the Tirpitz and which also allowed a torpedo attack on it from the air.

The convoys to Russian ports were escorted half way by battleships and the rest of the way by destroyers.

The Germans also had successes having broken the Naval Cipher Code No 3 used by British, American and Canadian navies that enabled them to find convoys.

At B P increased local security was introduced by using a scrambler even for inter-departmental communications.

Knowledge of the whereabouts and deception of enemy vessels, particularly U-boats allowed landings in Sicily and Normandy to proceed without danger of attack.

The arrival of the Americans after Germany declared war posed some difficulties. There was no problem with the Americans receiving the completed reports, but Bletchley Park was reluctant to let them into the organisational function as a security risk in case Ultra was compromised.

‘It is very difficult for deception to create new concepts for the enemy. It is easier and more effective to reinforce those which already exist’, e.g. Operation Mincemeat.

In the first half of 1942, during a code blackout, the convoy PQ17, totalling 137 000 tons, had only 11 out of 26 ships reaching Russian ports. For the whole of 1942 some 4 million tons of shipping were lost.

This was due to a change in the wheel combination for the Atlantic U Boat net.

The Germans continued to believe that their Enigma was secure.

At the same time American merchant ships had now lost their immunity.

By the capture of more submarines the Enigma was being read currently instead of a delay of 30 hours.

By March 1943 Bletchley Park had access to 70 bombes.

The Americans suggested going after the U-boat oil supply tankers that had enabled an extended cruise range. Bletchley Park, however, was concerned that that might compromise Enigma.

The introduction of Radar aboard aircraft carrier planes now covered the air gap south of Greenland and prevented enemy submarine operation on the surface. ASDIC had also been available to locate submarines under water. Total tonnage sunk had dropped by 2/3.

The U-boats had developed a short-signal code decreasing the time of a radio signal to reduce the possibility of direction finding. Thirty-one U-boats had been sunk in early 1943. Admiral Dönitz decided to withdraw all U-boats south of the Azores. Convoy tonnage losses dropped to zero.

The Short Signal code was captured from U 559 and U 205:

Convoy sighted
Position in the Atlantic Grid [B P already had a copy of the grid]
Direction of the convoy [This was compared to the already known direction]
Signed, U 276

These signals provided many more cribs for the bombe and helped to construct the bigram tables.

Alternative methods when Enigma Codes were unavailable:-

Banburisms narrowed down the number of wheel orders when a series of messages are sent. Further tested by –

Bombe, a large electro-mechanical machine using information from cribs

Cribs, guessed texts from plain language German matching a stretched cypher text

Bigram Tables, two letters selected from a book in use when captured

Network, U-boats using the same Enigma settings on the same day as small vessels and harbour traffic

On a visit to Bletchley Park in 1941 Churchill was startled to find such apparently chaotic scenes and said, “To look at you one would not think you knew anything secret”. He had coined the word ULTRA – ultra secret.

Having started off with a staff of 30 people they ended up with some 6 000. In 1943 the Enigma section had 10 senior cryptographers and 115 support staff.

At the end of the war, Churchill sent a congratulatory message to Bletchley Park, “Thank you for laying so many eggs with so little clucking’.

They had saved countless lives and contributed greatly to winning WWII.

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