Authors: Hervie Haufler
Hinsley called the availability of Fish decrypts "the outstanding signals intelligence achievement in this last phase of the war."
Unknowingly, the engineers who produced Colossi were reaching another milestone. Their machines were forebears of the modern digital computer, a success that should have been attributed to British science but that had to be suppressed by the long postwar secrecy imposed on all things cryptographic. On orders from Churchill after the war, the Colossi were destroyed and Tom Flowers burned the blueprints.
At Bletchley Park in the 1990s, however, the Colossus was reborn. Tony Sale, a determined engineer of the postwar generation, secured the aid of Flowers and others who had worked on the original development to help him build a working model. This Colossus is now seen on summer weekends by thousands of visitors during tours of the Park.
BP Begins Exploiting Its
The bright young people assembling at Bletchley Park very quickly realized that by building on the beginnings passed on to them by the Poles, they were on to a cryptologic opportunity surpassing anything known before. As Gordon Welchman said, "We were faced with an unprecedented situation quite unlike cryptanalysis of the old days when messages were broken one by one. If we could discover a 'daily key' which told German operators how to set up their Enigmas, we would be able to decode all messages using that key. . . . Even in the autumn of 1939, when no military operations were in progress, we were intercepting hundreds of messages each day." Welchman saw this mass of intelligence inflow as a "potential gold mine."
BP's first bonanza from the mother lode came in April 1940, when Hitler ended the edgy, idle "phony war" that had lasted for seven months. Hearing rumors that Britain was planning to occupy Norway, the German chancellor resolved to strike first. He would delay his planned drive into France and let the phony war continue until his troops had removed the threat of a flanking attack through Scandinavia. When the campaign began on April 9, Britain's intercept stations were suddenly flooded with the messages of a new Enigma code BP labeled as Yellow. Gratifyingly, the breaking of Yellow took Bletchley's cryptanalysts less than five days.
Very quickly the BP team learned how unprepared they were to handle the great influx. The sheer volume of the intercepts overwhelmed the cryptanalysts. Also, the messages they did decipher were filled with bewildering abbreviations, oblique references and arcane military jargon beyond the ken of the largely academic translators. The experience, moreover, pointed out the inadequacies of Bletchley's system for disseminating its information to the various commands. The people who could make the greatest use of the information simply weren't in the loop. In addition, security measures deemed necessary to prevent the Germans from knowing that their Enigma messages were being broken were now seen as serious deterrents to the effective use of decrypts. Up to that point, the scheme devised to protect security in case a BP summary fell into enemy hands was to attribute it to a spy code-named Boniface. It was a thin mask that, as the volume of traffic mounted, soon became an obvious fabrication. Further, British services had little faith in the espionage wing of British intelligence; as long as they thought they were reading the reports of a spy, they tended to reject or ignore even the most valid signals conveyed to them. BP minds began to realize they had to submit their internal systems to a drastic overhaul.
Young Harry Hinsley, the man who would long afterward take the lead in writing
British Intelligence in the Second World War,
was involved in one of the sadder aspects of the Norwegian disaster. Although BP was not yet breaking the German naval codes, Hinsley's study of the increased flow of naval wireless traffic, combined with direction-finding analyses that ascertained the buildup of signals was coming mainly from North Sea ports, convinced him in early April that a German attack in Norway was approaching. He phoned his warnings to the Royal Navy's headquarters, the Admiralty, in London. But his was merely a youthful voice, a voice, in the eyes of the Admiralty, of a civilian who knew little about naval operations. Moreover, the planes for British aerial reconnaissance were unable to range as far as the Baltic ports, so they could not verify his claims of a German naval buildup. Consequently, the Admiralty refused to heed his alarms or those of British agents on the continent, or even the advices of the diplomatic observers of "neutral" countries. If the navy had acted, Britain's warships could have ravaged the troop-filled transports and barges moving to the attack. Instead, the Germans achieved complete surprise, quickly overran Denmark and invaded Norway. On April 15 the British sent troops to aid the small, game Norwegian army. But it was all too improvised and far too late. The Germans crushed the Norwegian defenders and forced the British to evacuate.
Hinsley tried to prevent another grievous incident. The aircraft carrier HMS
had steamed to Norway to bring home RAF planes and aircrews urgently needed to help defend Britain against the expected German air assault. The ship, headed back toward England and escorted by two destroyers, was oblivious to German warships in its path and failed to send out air patrols. From Yellow decrypts, Hinsley saw the danger and again tried to warn the Admiralty. And again he was ignored. The battleships
guided by German cryptanalysts decrypting the Admiralty's orders, moved in on the British trio and sank them all, with great loss of life.
In fact, the Germans had broken the British naval code in 1938 and were reading the Admiralty's dispatches throughout the Norwegian campaign. During the critical period when the German landings in Norway were most vulnerable, German decrypts disclosed the positions of most of Britain's capital ships in the North Sea. As one British commander ruefully commented, "It is most galling that the enemy should know just where our ships always are, whereas we generally learn where his major forces are when they sink one or more of our ships." At that early stage of the sea war, the Germans clearly held the intelligence advantage.
The British made Norway a bitter but fruitful learning experience. New personnel flowed into Bletchley Park in increasing numbers. Military experts were brought in to unscramble the Germans' military shorthand. A new legion of translators and interpreters were sought out. Fred Winter-botham solved the dissemination security problem by organizing SLUsâ Special Liaison Unitsâwhich were assigned to the headquarters of each command and served as conduits by which summaries of BP decrypts were passed on to those who could make use of them. A new method was devised to indicate the relative importance attached to each report: one Z for lower-value material and up to five Zs for signals that clamored for immediate attention. Also, the Park's staffers began using special headings to designate Enigma information:
identified naval traffic for a time, and later, because Churchill called BP his "Ultra Secret," reports based on Enigma decrypts were then labeled
As to where the information came from, messages simply cited
Boniface was laid to rest.
And miracle of miracles, the tradition-encrusted Royal Navy came around changing its mind about the importance of BP's information. Hinsley, in a memoir, has reported that he was
full of admiration for the alacrity with which the OIC (Operational Intelligence Center of the Admiralty) responded to the loss of the
It immediately invited me to spend a month in the Admiralty. It sent me on the first of several visits to the Home Fleet at Scapa, where I stayed on board the flagships and walked the deck with Admiral Tovey and his staff. And on my return it did all in its power to ensure through the regular exchange of visits, and with the assistance of new scrambler telephones, that there should be complete collaboration between the OIC and the Naval Section at Bletchley.
When a question arose as to the source of a specific bit of news, it was sufficient now to answer only, "Hinsley."
One other result of the catastrophe in Norway was that Neville Chamberlain stepped down as prime minister, and was succeeded by Winston Churchill.
Ultra and the Battle of France
On May 10, 1940, when Hitler was confident that his Scandinavian flank was under control, he unleashed the fury of the German blitzkrieg on the British Expeditionary Force (BEF) and the armies of France.
Again the Germans possessed the advantage in intelligence. They were breaking the high-level French military code and consequently knew in detail the disposition of the French divisions. At this same critical moment, the German air force blinded BP by making a change in its Red system. German security controllers had evidently realized the vulnerability of having Enigma operators repeat the three-letter encoding of their machine settingsâthe flaw that had enabled the Poles to begin breaking the systemâand had issued new regulations for the second encipherment to be dropped. Astonishingly, BP's codebreakers needed only twelve days to cope with this change. After May 22 they began deciphering as many as a thousand Red signals a dayâ"a flood of operational intelligence," as Hinsley put it.
It was intelligence that should have proved of high value to the British divisions in France because it contained clues to the intentions of both the German air force and army. By then, however, the situation on the continent had become a shambles. The French had used high percentages of their annual armaments budgets to build the Maginot Lineâthat concrete bastion designed to keep German invaders at bayâand had neglected to supply their military units with up-to-date arms. Even so they had completed only eighty-seven miles of the line, leaving open to attack the entire northern area from the English Channel to the Ardennes forest. The French didn't want to wall themselves against their Belgian, Dutch and Luxembourgian neighbors and persuaded themselves that the Ardennes forest was invulnerable to tank attack.
The Germans called their plan for the offensive "sickle stroke." They would frontally attack the Allies through the Holland-Belgium corridor and swing a mighty sickle of armored divisions through the Ardennes and then northward toward the Channel to cut the French and British armies in two.
The plan was brutally successful. The attack in the north drove the Allies into a grudging withdrawal, while the armored push through the Ardennes swiftly pierced the thin French lines and began the circuit west and north to encircle the northern armies. By the time the large flow of Ultra summaries was again reaching the BEF commander, Field Marshal John Gort, the situation was too chaotic for intelligence to have much effect.
The decrypts did, however, help in two important ways. In his book
The Ultra Secret,
Winterbotham related that Gort later told him of Ultra's value in convincing London to accept his decision to get out of France as quickly as possible. BP had decrypted an order from General Walther von Brauchitsch that commanded his two army groups "to continue the encircling movement with the utmost vigor." This came at a time when the French were pressuring Gort to launch a counterattack southward. To do so, he saw, would imperil the British Expeditionary Force in a cause that was already hopeless, and would rob Britain of the men who would be needed to stand off a German invasion attempt. Gort's decision to turn toward the sea was seconded by Churchill. Gort began pulling his troops back toward the coastal town of Dunkirk.
In view of Brauchitsch's order, the second decrypt was highly puzzling. Sent by Hitler himself, it called for the attack against the encircled Allies to be "discontinued for the present." Just when the BEF appeared to be backed up against the sea with little hope of escape, the pressure let up, and the panzer divisions stayed put. Gort gained the breather he needed to build a perimeter defense around Dunkirk and begin the massive evacuation of the BEF.
Hitler had his reasons for holding up the attack on the forces beleaguered at Dunkirk. Without an equivalent of Ultra to inform them, the Germans greatly underestimated the numbers of Allied troops trapped on the Channel coast and considered them a secondary target compared with completing their conquest of the French. The urgency of the attack was eased by Goring's assurance that if any evacuation was attempted, his planes would smash it. Further, German generals welcomed a pause that would let them regroup their armor and give the infantry time to catch up. Hitler himself, remembering his Great War experiences, viewed the coastal rivers and marshes as threats to German armor.
Above all, Hitler continued to hope that the British, recognizing their commonality with the superior German race and their united need to withstand the hated Bolsheviks, would agree to peace. This was a cause that might be aided by avoiding the massacre of those pitiful remnants of the BEF at Dunkirk.
The Germans delayed for two crucial daysâa reprieve that spelled the difference for Great Britain and the war. During that time, the British launched Operation Dynamoâthe gathering up of thousands of small craft, everything from fishing boats to private yachtsâwhich crossed the Channel and rescued the Allied troops from the Dunkirk beaches. French and Belgian vessels joined the motley armada. By the time the last ship drew away on June 4, some 337,000 Allied soldiers, including more than 100,000 French troops, had been saved from capture.
And the codebreakers of Bletchley Park had strengthened their status. For the first time, intelligence derived from their decrypts had become a factor in the making of strategic decisions.
Battle of Britain: For Ultra a Stronger Role
As it had in the time of Napoleon, the twenty-plus-mile strip of water known as the English Channel once more came to the rescue of Britain. Although Operation Dynamo had brought the soldiers home, virtually all of their heavy equipment had been left on the continent. But with the sea as their moat, and with the Royal Navy and Air Force to make it impassable, the British prepared themselves to stave off the Germans' expected attempt to invade their island.