Top-Secret ULTRA

British Heritage magazine special issue: ‘Britain at War, September 2000

It was easily the most closely guarded and enduring secret of World War II. Thousands of books, articles and reminiscences by the generals, admirals and civilian leadership masterminding the war were all silent on the subject. The usually loquacious Winston Churchill said nothing about it in his six volume History of the Second World War. The 12,000 men and women who were there, sworn by an oath to king and country, neither spoke nor wrote anything for three decades after the war. They remained silent until the mid 1990s.

In the last years of the Twentieth Century much of what happened at Bletchley Park (shown above in 2000) remained as mysterious as when the 581 acre Buckinghamshire estate became the headquarters for an unprecedented intellectual attack into the heart of Hitler’s encrypted intelligence empire. Code-named ULTRA, the collective cover name for the interception and decoding of encrypted German military radio communication, Churchill’s secret of the century became the most successful intelligence penetration in history.  Its historic triumph – the discovery of the secret entrance into the labyrinth of the Enigma device – the primary means for encryption of dispatches to the German armed forces.

An arrogantly confident German High Command had determined that neither man nor machine would ever pierce the multi-layers of its three and four rotor mystery mechanism. But Enigma was neither impenetrable nor puzzling.  And as Waterloo was said to have been won on the playing fields of Eton, so too the Allied victory in World War Two was won by the codebreakers at Bletchley Park.  It all began very modestly inside the hulking red brick Victorian mansion.

Part of a landed manor awarded by William the Conqueror to a notable commander after the Battle of Hastings, the Bletchley estate was later confiscated by the Crown, and passed through various family lines before being sold in 1883 to Sir Herbert Leon, a financier and member of the London Stock Exchange. Like a many-chambered nautilus the existing unassuming residence became intermittently appended through the years; here a servants wing and ice house, there a new entrance hall and an addition to the drawing and dining rooms. Then a library, ballroom, and more bedrooms were added. Numerous outbuildings sustained the social and agricultural pursuits of the Leon family.  Unfortunately, the additions only added to its hulking, irregular appearance, completely lacking in harmony or refinement.

It was however, perfectly sited directly across the road from the mainline Midland & Scottish Railway. An easy 42 mile commute connected Bletchley with London and the Whitehall and Downing Street nerve centers.  And the mansion was midway between Oxford and Cambridge, fertile soil for codebreaker candidates. Even better for later motorcycle dispatch riders, the A5, one of the country’s principle trunk highways, was only a mile away. When it was appropriated by the government in 1938, Bletchley Park’s greatest days were just ahead.

Seven decades ago as the world edged to the brink of a new dark age, the democracies faced no greater challenge than overcoming the malaise of governmental neglect. In the last days of peace, the British army maneuvered with only 259 tanks and even fewer antitank guns and artillery pieces – all obsolete. The Home Guard trained with antiquated sporting guns, most lacking ammunition. Only 620 aircraft were combat ready, and the RAF was short of fighter pilots and aviation fuel. The Admiralty ignored the rapidly developing U boat threat, allowing the proud Royal Navy to sail a fleet of mostly ancient dreadnoughts, the mightiest of which would soon be on the ocean bottom. And America could hardly be expected to come to the immediate aid of its cultural cousin. Divided by the anguish of isolationism, and only a generation removed from the sacrifices of World War One, America’s standing army ranked eighteenth in the world, just behind tiny Holland.

In late 1938, against a background of imminent peril, the first thirty members of the government cipher school began modest radio eavesdropping operations in the mansion’s castellated tower. Much later, as the tangled layers of the Enigma puzzle were progressively revealed, the personnel at the mansion or billeted in nearby villages rapidly increased. Lawns and flower beds outside the drawing room were uprooted to build Hut Four, where the German naval Enigma was broken. The Leon’s cherished Victorian maze disappeared one weekend to make room for two tennis courts ordered by Churchill during an early inspection. At an impromptu gathering outside the mansion after the visit, the Prime Minister saluted his staff as the “golden geese that never cackled.”

The odd-bodies and boffins called to Bletchley Park were a peculiar lot, even by the often droll standards of the time.  In World War I linguists cracked codes based on words, but in World War II enemy messages were produced by machines generating a puzzlement of gibberish in five letter combinations. The tightly organized civilian occupations of the new codebreakers were, therefore, highly appropriate to the task at hand. Arriving daily were crossword puzzle experts, university mathematicians, literature dons, classicists and librarians. Tapped from newspaper advertisements, musicians, language instructors, historians, accountants, bankers, and newspaper and publishing executives passed through the gates.  Topping the odd aggregation, even philosophers and pedagogues from museums, and rare book store owners applied and were eagerly accepted. The thinkers and savants were supported by concentric staff overlays in scores of temporary structures called “huts,” (see below) extending erratically from the mansion occupied by administrators and cryptanalysts.

Translators, linguists and specialist teams focused on the four main branches of the German Wehrmacht, or on Abwehr – the intelligence service – even on OKW, the Nazi general staff.  Naval WREN’s operated “bombes,” the hot and noisy codebreaking machines. Typists transcribed German language plain-text solutions into English. In other huts hundreds of thousands of intercepts written in longhand on 5×7 inch file cards were catalogued into stacks of shoe box size cartons. Machine operators and technicians maintained the delicate codebreaking apparatus. Cooks prepared meals for canteens and mess halls in the mansion and the former Leon fields. Troops, antiaircraft batteries and five RAF air bases formed a protective cordon around the complex. In the event of invasion, a train with engine under constant steam waited at the station to transfer the vital codebreaking equipment to Liverpool and passage to America.

Thousands of radio intercept operators staffed the outer ring at various coastal ‘Y’ stations, such as Knockholt in Kent or Kedleston in Derbyshire. There, the raw intelligence originated under usually appalling conditions. Enemy transmissions alternated among 226 radio frequencies, with Enigma coded messages averaging only ten seconds. Successful detection had to overcome constant frequency changes and jamming by the enemy, static and drifting from storms and other natural phenomena, howling whistles and squeals, and the ordinary sounds of music or dialogue. Intercepted messages were dispatched to Bletchley by motorcycle outriders – up to 50 an hour – and later by secure teleprinter for codebreaking and analysis. Noteworthy decrypts were immediately delivered to the Prime Minister in his own secret complex at the Cabinet War Rooms in central London.

The huts today are similar to their 1940’s appearance – some with frame construction, others in brick

The joint military and civilian staff faced each other across trestle tables in the drafty and poorly lighted huts. Women outnumbered men eight to one. The code-cracking teams neither knew nor cared about friends assignments in other huts or at the next desk. The military wore uniforms without badges of rank or unit markings. Civilians dressed in tweeds and corduroy. Everyone worked furiously eight hours on and eight hours off around the clock from the day the war started until it ended almost six years later. And no more than four persons out of 12,000 ever had full details of the Ultra secret.

Many of the staff lived in stately homes vacated for the duration, such as Steeple Clayden and Beaumanor; others in lonely cells above crossroads pubs. Betty Warwick Boyd and other Royal Navy WREN personnel were billeted at Woburn Abbey in Bedfordshire, home of the Duke of Bedford. “Secrecy was so great that at the end of a watch we never spoke about what we did, nor did we talk to those in other huts or know what they did. We would sometimes spend an off duty day in Oxford or Cambridge, or just walking the beautiful grounds at Woburn and enjoying the fresh air.” She never saw the numerous Canelettos, sumptuous Sevres dinner service, or the chinoiserie, tapestries and stunning porcelain collection, all locked away in the Abbey’s vast rooms.

Life at Bletchley Park was not without opportunities to socialize and temporarily disengage from the crushing stress of duty. Friendships led to romance and marriage for some. Others would meet and marry years later only to learn that each had been at Bletchley at the same time without meeting. A drama club was organized. Dances were regular events, with American swing band or Bing Crosby recordings among the phonograph favorites. Considering the peacetime occupations of the staff, bridge and chess were popular diversions.

The long awaited American assistance began with covert information exchanges well before the United States entered the war in 1941.  Franklin D. Roosevelt gave Churchill secrets of Magic, the American code-breaking system which would later defeat the Imperial Japanese navy at Midway. In return, details about Ultra and the Enigma intercepts were shared by Churchill with FDR. A massive undercover British operation at Rockefeller Center in New York City controlled joint intelligence exchanges.  U.S Army, Navy and civilian cryptanalysts were dispatched to Bletchley months before Pearl Harbor. One of them, William Friedman, America’s leading cryptanalyst, collaborated with Alan Turing, the English codebreaking genius and inventor of modern digital computing.  (see accompanying article – Alan Turing – ENIGMA)

An intelligence bonus on the eve of war avoided months of manual calculation when Polish scientists gave British forces a working Enigma model and plans to construct an electromechanical code-breaking machine called a “bombe.” A trickle of only 50 decoded messages a week in 1940 became a flood of 3,000 per day by 1943. The sprocket driven “bombes” were overwhelmed by a torrent of messages, persuading engineer Tommy Flowers and his team at Dollis Hill to invent a revolutionary digital, electronic, programmable computer. Code-named Colossus, the sole purpose of the 2,500 tube mainframe was to read the personal messages sent by Hitler to top battlefield commanders, encoded on an even more inscrutable Lorenz 12 rotor cipher called Geheimschreiber.

Enigma text
Enigma generated hand-written message decrypts (photo by author)

Even this most secret communication became just another open book in a vast archive of information.  Messages faced almost immediate discovery by Colossus, with solutions automatically printed on an IBM electric typewriter – and in the original German. Aware of precise enemy intentions, Bletchley had fully analyzed Enigma dispatches hours before they were read by Generals Goering, Guderian or Rommel.  Churchill was reading over brandy at lunch in London the same dispatches Hitler would not receive in Berlin until dinner.

Predating the American ENIAC by more than two years – widely but incorrectly thought to be the world’s first electronic computer – the very existence of Colossus was itself secret until 1989. Never suspecting that Enigma had been compromised, and with negligent trust in placing the country’s destiny on the thin armor of a fallible machine, the Germans used the fatally flawed system until the end.

The Ultra advantage changed the lives of millions who fought and unknown others affected by its global reach. By knowing the names of enemy units, their strength, exact location, order of battle, ammunition and fuel status, entire divisions were neutralized with minimal manpower effect. The breaking of the German Enigma naval code disclosed the specific grid locations of U-boat wolf packs and their refueling “milk cows.” Convoys were diverted as North Atlantic ship losses dropped 75%. Even the operational depth of U boats was learned – a crucial detail for attacking destroyers. Submarine losses reached unacceptable levels forcing redeployment to safer waters. Crucial cargo from North America safely reached diverse ports from Southampton to Murmansk. Ultra became the silent partner in sinking the Bismarck, in victory at El Alamein, and decisively defeated the wolf-packs in the Battle of the Atlantic.  In planning Operation Overlord, strategists knew from ULTRA intercepts that Germany expected invasion at the Pas de Calais.  By using the ruse of a fictitious army commanded by a very real General George Patton, nineteen German divisions were thus removed from the battle.

When Patton’s U.S.Third Army began the race from Normandy across France, it was guided by daily and often hourly briefings from Ultra intelligence. Almost all of the decrypts were hand delivered by specially trained soldiers.  And resulting from its understanding of the German high command’s intentions and strategy, Ultra eliminated the crucial element of surprise.

Postponement or failure of the 1944 Normandy invasion was a real possibility for Allied planners. Without the Ultra edge, the European war and even more horrific casualties on both sides would have continued until at least 1946. Scores of high speed U boats under construction and new jet fighters already in the skies, could easily have continued the fighting into 1947.

With the war over Churchill ordered the destruction of all the code-breaking machines into “pieces no larger than a man’s hand.” The Bletchley mansion was shuttered, the staff discharged and the huts emptied and boarded up. The Ultra secret became decades of ultra silence, destined to expire with its high priests and practitioners. But not quite.

Across from the still operating Bletchley Park rail station, a narrow lane overgrown in vines leads the contemporary visitor past rusty barb wire fencing to the unchanged red brick Victorian mansion.  Echoing with abandonment, the same huts emerge beyond the great house like sections of a crooked ladder, as if carelessly littering the Leon’s gentle lawns. This is where history was made and where it lives and confers silent witness to the pioneers who broke the code and kept the secret.

Sign entrance
“AUTHORIZED PERSONNEL ONLY” The unchanged entrance to “Station X”

Among the exhibits at Bletchley Park is a captured Enigma cipher machine, and a rare and hideous-looking 12 rotor cipher built by Lorenz, and specially designed for Hitler to communicate in apparent confidence with his battlefield commanders. The Geheimschreiber, or “secret writer,” needed six operators to manage 501 settings for message encryption and  radio transmission.

But the most absorbing exhibit at BP is a rebuilt Colossus computer.  After the war Churchill ordered that each of the existing 10 Colossus computers and 150 mechanical “bombes” at Bletchley Park and other locations be broken into “pieces no larger than a man’s hand.”  In a remarkable feat in 1997, Bletchley Park’s curator, Tony Sale, located spare parts, circuit diagrams, and official photos, and with the help of the original engineers, rebuilt what many consider to be the world’s first digital, programmable, electronic computer.

Colossus computer
The rebuilt Colossus computer at Bletchley (author’s photo)

In 1946, the American military unveiled ENIAC, a 100-foot-long, 10-foot-high behemoth containing 17,480 vacuum tubes and designed to perform artillery trajectory calculations.  Although ENIAC was more an electronic calculator than an authentic computer, history accorded it the distinction of being the world’s first electronic computer.  Historians could not have known that the top-secret Colossus had been operating since 1943.  There were major differences between the two machines;  the 30-ton ENIAC consumed 150,000 watts of power, but stored only a paltry 80 characters of information.  The 2,500-tube Colossus was 17 feet long, 6 feet 6 inches high, and dependably read miles of punched tape at 5,000 characters per second.  Carrying the encrypted German messages, the tape coursed around whirring pulleys and past arrays of photoelectric cells at 30 miles per hour, with plain text results printed in German on an IBM electric typewriter – the only American-made component in the computer.

The very existence of Colossus was not made public until 1989.  The rebuilt version once again decrypts original German ciphers for awed Bletchley visitors.

About Jerome O'Connor

Jerome M. O’Connor, a Chicago area author, journalist, historian and college educator, produces and lectures with original programs describing the little-known, overlooked, or under-reported people, places and great events of modern history. To qualify, all locations must exist and and be accessible. Deeply researched and dynamically presented multi-media programs result in numerous return invitations. Currently available are personally conducted tours to view and enter facilities depicted in his Chicago Tribune features, ARSENAL OF DEMOCRACY and MOTOR ROW MEMORIES. Updated is the photographic result of a return visit to Bletchley Park in England, where 12,000 code-breakers revealed the 'secret of the century,' the breaking of the Nazi Enigma cypher machine. O'Connor was the first journalist to reveal its existence in a widely viewed 1997 cover feature in Naval History magazine and in British Heritage magazine in 1998. The "Author of the Year" award from the U.S. Naval Institute was given to O'Connor in a U.S.Naval Academy banquet. His critically praised first book, THE HIDDEN PLACES OF WORLD WAR II, enters the existing locales that were essential to victory in WW II but overlooked by generations of historians. Published by Lyons Press, an imprint of the Rowman and Littlefield Publishing Group, it honors the sacrifice of 16 million men and women who saved civilization in its darkest hour. Portions of the book are on this site. A quality paperback released in February 2022 is on Amazon and at selected booksellers, for a total of 3 versions now available.