Digesting these inflows, Bletchley sent its reports to the mansion outside London housing the RAF Command Headquarters. The hub of Britain's defensive air operations was a giant gridded map over which young women with croupier-like poles followed instructions to move symbols marking the course of aircraft squadrons, both German and British, keeping the onlooking officers abreast of the fast-changing aerial scene.
Hinsley has recounted one other significant contribution GC&CS made before the offensive began. Britain's Air Ministry had to estimate the number of German bombers available for the battle, and the bomb capacity they could be expected to deliver. The ministry had believed the RAF faced 2,500 bombers capable of dropping 4,800 tons of bombs per day. These alarming figures prompted the preparation of disaster evacuation and hospitalization measures. BP decrypts scaled down the estimates to a more realistic 1,250 bombers and 1,800 tons. The Air Ministry described the information as "heaven-sent" and felt able to "view the situation much more confidently than was possible a month ago."
The Battle of Britain began on July 10, 1940, when the GAF sent some seventy planes against British targets. The lines were drawn, pitting Goring firmly against Britain's Air Chief Marshal Hugh Dowding.
Dowding was a former Great War pilot who had risen to be a squadron commander and a brigadier. Frederick Pile, who commanded Britain's antiaircraft defenses during World War II, wrote of him that he was "a difficult man, a self-opinionated man, a most determined man, and a man who knew more than anybody about all aspects of aerial warfare."
Dowding clearly perceived that this would be a war of attrition, of whether the RAF could outlast the GAF. He wrote in his diary that time favored the British "if we can only hold on." To his advantages in radar and signals intelligence he added his own shrewd tactics for holding on. Instead of sending his Spitfires and Hurricanes aloft in masses to meet the German fleets head-on, which was what Goring wanted in order to shoot down more RAF planes, Dowding dispatched his squadrons piecemeal, ordering relatively small numbers of planes into the air at a time. His strategy gave his fliers the advantage of slipping in among the German formations and downing more planes than the RAF lost. Dowding's methods were hotly contested by other RAF commanders, but he alone among them was privy to BP decrypts, and these confirmed that his staggering of RAF planes and pilots was working. While reducing RAF casualties, it increasingly frustrated the Germans, especially Hitler.
At the outset of the battle, Goring's first goal was not only to shoot down RAF planes but also to destroy airfields, raze hangars, topple radar towers and smash aircraft-producing factories. In the days of July and August his generals sent wave after wave of German aircraft against these targets. Without a German Ultra to inform him, Göring never knew how close he came to succeeding. The RAF losses in planes and crews were so heavy, and their remaining pilots so exhausted from conducting as many as seven sorties a day, that by the end of the first week in September, Fighter Command feared it would hold out only three more weeks. Dowding confided to a colleague, "What we need now is a miracle."
The miracle came as, abruptly, the Germans changed their tactics. Their reason for the change came about because of a blunder. The crews of two German bombers on a night run became disoriented and dropped their bombs on London, going against Hitler's orders to avoid hitting English cities. Churchill retaliated by sending English bombers over Berlin. Hitler, in one of his rages that often led him to make bad decisions, ordered Goring to leave off his attacks against RAF facilities and focus future bombing runs on London.
As a consequence, just at the point when the Luftwaffe might well have gained dominance over the RAF, its planes changed course. The incessant pounding of London gave Dowding and his team the respite they desperately needed to recoup and reequip.
When repeated attacks on London failed to achieve the objective of breaking the morale of the British people, Göring again ordered new tactics. He sent his planes to concentrate on other cities, to devastate them one by one and so weaken the islanders' will.
Ultra's effectiveness in giving advance warning of Luftwaffe raids has been questioned. At this early stage of the war, Bletchley's mastery of Enigma was still too weak, and oftentimes too slow, for the decrypts to be of tactical value. Often, the raids were completed before the messages relating to them could be decrypted. Also, Goring relied largely on landlines to direct the attacks, leaving little to be intercepted.
But there was one development in which Ultra's aid was undeniable. This was the Germans' use of a radio beam system to guide Luftwaffe pilots, astonishingly untrained in navigation, to their targets and even to tell the crews when to drop their bombs. The German system was code-named Knickebein, or "crooked leg." On their runs over Britain, the German pilots steered between two streams of dot-and-dash signals; if the plane strayed too far to the left, dots grew louder, and if to the right, dash sounds increased. As they neared their targets, crossbeams told the crews the moment to unload their bombs, and in a later improvement actually triggered the releases. Bletchley decrypts tracked Knickebein's development all the way.
In his memoir Most Secret War, Churchill's young scientific adviser Dr. R. V. Jones told how he was alerted on June 12, 1940, to the existence of Knickebein and how he immediately began to plan counter-measures. His method was to develop signals more powerful than those of Knickebein and by this means to lure Luftwaffe bombers away from important industrial targets. Jones also used crossbeams that caused the crews to drop their bombs on open countryside. His measures succeeded. One German bomber crew dispatched to the west of Britain became so addled by Jones's trickery that they mistook the Bristol Channel for the English Channel and landed on British soil instead of France. Mindful of Jones's success in both thwarting Knickebein and developing two more sophisticated defense systems later, Churchill called Jones his "boy wonder—the man who broke the bloody beams."
One tragic error came on November 14, when the jamming transmitters were mistakenly turned to the wrong frequency, allowing Knickebein to guide a large assembly of bombers to their target, the city of Coventry. A Bletchley decrypt warned of three forthcoming attacks and gave the code name of KORN as the target for that night's intensive raid. Today, in Britain's Public Record Office at Kew, a visitor can gaze at BP's decrypt, with the code word thrusting itself on the eyes. But at that moment KORJSTs meaning was not known. As a result, the German bombers got through virtually unchallenged to drop tons of high explosives and incendiaries on Coventry, burning out the city's center, killing 554 and wounding hundreds more.
A story that gained circulation was that the Coventry bombing thrust upon Churchill an agonizing decision: either he warned the citizens of the city to evacuate, which would have tipped off the Germans that their codes were being broken, or he allowed the raid to proceed. Though a touching story, it wasn't true. Warnings of the bombers' destination came too late to permit extraordinary defense or evacuation efforts. The most that could be done was to alert firefighters, rescue squads and antiaircraft batteries. Churchill faced many hard decisions, but this was not one of them.
A week after the Coventry raid, Bletchley Park endured its own Luftwaffe bombing. The crew of a lone aircraft who probably wanted only to jettison their remaining bombs on a nearby railway junction before turning for home missed their target. One of their bombs smashed into the outer building to which Gordon Welchman had originally been banished. Another landed in the garden of the vicarage next door. Two more landed inside BP, one of them close enough to Hut 4 to break some of its windows and move it several inches off its foundations. No one was injured, but to have the war come so close no doubt boosted the spirits of the men at BP. "They tended to think of themselves," recalled Pat Bing, one of Hut 8's young women, "as 'skivers'—the word for those who pick up money without doing any work for it—and in their case for being in the war but not actually fighting. So the bombing braced them up a bit."
The bombing may also have helped the men at BP counter the s
neers of locals who observed healthy young blokes engaged in some dubious unspoken rear echelon activity. As a bit of doggerel circulated at the Park put it,
I think that I shall never see
a sight as curious as BP.
. . . . . . . . . . . . . . . . . . . . . . . .
Five long years our war was there
subject to local scorn and stare.
Meanwhile, Ultra and other sources were reeling in a rich cache of intelligence regarding Operation Sea Lion. German top officers may have been lukewarm about plans for the invasion, but their underlings had no choice but to take the orders seriously and to throw themselves headlong into preparing for it. The Public Record Office file of Red translations includes the calls for embarkation rehearsals and practice landings, orders for transport and loading officers to remain at their ports until further notice, the training of crews for towed gliders, the plans for quick-turnaround airports to be used in shuttling troops and supplies across to England. The decrypts show how unprepared the Germans were to carry out an amphibious invasion. But that was what Hitler had ordered, and his service organizations substituted frenetic action for wiser consideration. Powered barges used on rivers and canals were hastily steered to Channel ports. Demands went out for engines to be mounted on the many other unpowered barges normally pulled in long strings by tugboats. It was a motley assortment, but the best the Germans could manage on such short notice.
On the night of September 7, after a day in which wave after wave of Luftwaffe planes had bombarded London, the code word Cromwell was sent to military units throughout Britain. It was the alert that the German invasion was about to begin. Church bells rang—a signal everyone recognized. Families crouched in candlelit shelters. The home defense forces were mobilized for "immediate action." Tomorrow the showdown would come.
But the German air force had not cleared the skies of the RAF. This was demonstrated on September 8 when, of two hundred bombers raiding London, eighty-eight were shot down. Adding strength to the RAF were Polish, Czech and Canadian pilots. The GAF raid was all that happened on that supposedly climactic day. The German invasion fleet never appeared.
The real climax of the Battle of Britain came on September 15. Göring, in desperation, hurled every plane he could muster against London, Southampton, Bristol, Cardiff, Liverpool and Manchester. Dowding, in response, departed from his piecemeal tactics and sent the RAF up in full force. When Churchill visited the RAF operations room and asked about reserves, he was given the answer: "There are none." The RAF lost twenty-seven fighters but destroyed fifty-five German aircraft.
Hitler was convinced: Göring had failed. On September 17, Hitler postponed the invasion of Britain, telling a subordinate that while the conquest of France had cost thirty thousand men, "During one night of crossing the Channel we could lose many times that—and success is not certain."
Word of his decision did not show up in Ultra decrypts. It had to be inferred from messages such as the one disclosing that equipment intended for installation on invasion barges "should be returned to store." Also, as October and November wore on, the rapid-fire rate of midsummer intercepts eased. Embarkation practices were postponed or canceled. Warships assembled for the invasion were sent on other missions. The threat evaporated.
Churchill did not wait long to be convinced. He ordered that 150 tanks being held to ward off German invaders should instead be dispatched to his hard-pressed divisions in North Africa.
The depleted Luftwaffe was reduced to making what were mainly nighttime attacks on London—the Blitz, as Londoners called it. Although the bomb runs killed many people and did great damage to the city, they came to be seen more as nuisance raids than elements of a consistent plan. Their effectiveness steadily declined. The Battle of Britain was over and, with the codebreakers' aid, handily won.
Albert Kesselring, who, in the first of his many command postings for Hitler, had led one of Göring's Luftwaffe fleets in the Battle of Britain, presented an interesting view of the effects of Britain's superior radar technology and signals intelligence on the Luftwaffe. Writing his memoirs in 1953, long before the role of Ultra had been revealed, Kesselring recalled that "losses soon increased to an intolerable extent owing to the quick reaction of the British defense—fighters and A.A. [Antiaircraft]—and quick concentration of fighters over the target and on the approaching route. With the alternative before us of letting the enemy's uncanny reading of our intentions bleed the Luftwaffe to death, we had no choice but to switch our targets, times and methods of attack."
"Uncanny reading of our intentions"—this could well be Ultra's epitaph, not just for the Luftwaffe but also for the whole German war effort.
During the depths of the Battle of Britain, Dr. Jones wrote in his memoir, "I used to look at my wall map every morning and wonder how we could possibly survive." By February 1941, he was finding "some hopeful signs," including an early victory in North Africa and "the strong voice of Franklin Roosevelt" in his support of Britain. Jones added, "Above all, there was the great advantage of being able to read much of the Enigma traffic. If only we could hold on, sooner or later this could turn the tide."
Ultra Guides a Victory in North Africa
Entering World War II, British intelligence was better prepared to sense what was happening in Benito Mussolini's Italy than in Hitler's Germany. GC&CS was reading the ciphers used by the Italian army, navy and air force in the Mediterranean, Libya and East Africa. Central Intelligence had also set up an interservice Middle East Intelligence Center in Cairo. The conclusion drawn from the decrypts, however, was that the state of Italy's armed forces left her unprepared for a long war and that Italian leaders would be anxious to preserve her neutrality.
These reasonable conjectures underestimated the ambitions of Mussolini. He felt overshadowed by Hitler's early successes and resolved to seek some conquests of his own. In April 1939, when Hitler took over Czechoslovakia, Mussolini sought to match him by seizing Albania— which gave in without a fight. In May 1940, with Hitler's defeat of France imminent, II Duce declared war on Great Britain and France and even dispatched squadrons of Italian bombers and fighters to make token raids on England. He also tried to invade the southeast corner of France bordering on Italy, but his troops were repulsed by the French, with heavy losses. Undeterred, he planned for actions in North Africa, contenting himself with the thought that the victories he could achieve there fitted more appropriately into his dream of building a new Roman empire.
Mussolini's North African prospects looked highly favorable. The collapse of France freed the more than two hundred thousand troops in Italian-held Libya who were guarding the frontier against the French in Tunisia. They could join the Italian Tenth Army, which was in place to counter the British in Egypt. Conquest of Egypt would crown Mussolini's possessions in Eritrea, Italian Somaliland and Ethiopia, as well as Libya. To oppose the Italian might, the British had fewer than fifty thousand underequipped troops who were also supposed to defend British interests in nine other Middle Eastern countries. On June 28, Mussolini ordered the invasion of Egypt.
The situation was an acute worry for Winston Churchill, especially when he found out that those 150 tanks he had consigned to his Middle Eastern command, that "blood transfusion," as he put it, weren't going to be sped by convoy through the Mediterranean. He was "grieved and vexed" when instead the ships were routed the long, slow way around the Cape of Good Hope.
He needn't have worried. Control of the Italian armies to invade Egypt was placed in the hands of the cautious Marshal Rodolfo Graziani, a much bemedaled veteran of earlier conquests in Africa. A realist, the marshal saw how ill prepared his troops were, with archaic guns and antiquated tanks. He employed delaying tactics, arguing that the attack shouldn't begin until the Germans had invaded Britain. Consequently, all through the on-again, off-again plans for Operation Sea Lion, his vast forces simply camped out in the desert and waited. Fuming, Mussolini on September 7 gave him the choice either to attack
or to resign his post. On September 13 Graziani finally did order his troops forward. In four days, to much trumpeting in Rome, he moved sixty miles into Egypt and took the outpost of Sidi Barrani. But for the British it was only a planned withdrawal. When they settled at their base in Matruh, Graziani stopped his advance, still some eighty miles short of the British. All through October and November the Italian armies hunkered down in the desert while Graziani prepared a new base for his offensive. The British tanks and other equipment arrived in October.
Britain's commander in chief in the Middle East, General Archibald Wavell, had placed his Western Desert Force under the command of Richard O'Connor, a resourceful bantam of a general who much favored offense over defense. The day after Italy had declared war, O'Connor directed sorties that captured scores of Italians, including a general. Now he settled into planning his main attack. In this he was greatly aided by the British codebreakers. Their decrypts, relayed to him by the Cairo center, gave him copious and accurate information about the locations and strengths of the various Italian army concentrations. BP's breaking of Luftwaffe Enigma signals assured him that the Germans, as yet, were not planning a transfer to North Africa.
Aerial reconnaissance also came to O'Connor's aid. Photos showed the routes the Italians used to drive through the minefields protecting their main encampments. The paths left a wide gap that he, too, could use to slip between the Italian camps and then wheel his armor around to attack them from the rear.
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