Secret Life of Bletchley Park - McKay Sinclair [50]
The end of August brought the conclusion of the Battle of Britain, and with it not merely a sense of relief but also a valuable raising of spirits. Churchill now gave the command for an air raid on Berlin. This in turn led Hitler to order the Luftwaffe to begin an even stronger attack on London. The unforeseen side-effect of this German strategy, however, was that it relieved pressure on the RAF airfields which previously had been the Luftwaffe’s main targets.
As mentioned before, Bletchley Park could offer little in the way of practical help to the air force at this time. However, come September, one particular decrypt was of great tactical importance. The message ordered the dismantling of air-lifting equipment on Dutch airfields. Its meaning was very swiftly deduced by the Chiefs of Staff: Operation Sea Lion was to be postponed.
In other words, the Few had succeeded brilliantly; the Luftwaffe having been repelled, there was little chance, with the season of storms now upon the English Channel, that the Germans could launch an effective troop landing. Hitler, the Chiefs calculated, would have to shelve preparations for the winter. It was precisely this sort of information, provided by Bletchley, that gave the forces what was termed a ‘crystal ball’. ‘So efficient did Bletchley become in handling this material,’ wrote Aileen Clayton, ‘that there were even cases where, during poor conditions for reception, the German recipient of a signal was obliged to ask the sender for the message to be repeated, whereas our listening stations had recorded it fully the first time. This placed British Intelligence in the position of knowing the contents of a signal before the intended recipient.’2
By late September, Hitler was starting to turn his attentions east, towards his projected invasion of Russia. Although the Luftwaffe had lost a great many men and planes throughout the Battle of Britain, however, this did not stop their aerial bombing campaign.
The Blitz started on the afternoon of 7 September 1940. Dread-filled Londoners gradually became aware of a distant muffled roar, like thunder, approaching from the east as 350 German bombers darkened the horizon. The RAF, expecting an assault on their bases, had missed the attackers. Within minutes, the German planes were flying over the vast docks and warehouses of east London. As they dropped their incendiary bombs, the warehouses, filled with imported sugar, molasses and timber, went up in a series of blossoming yellow and blue infernos.
The daylight raids were not to continue, for too many of the German planes were picked off on their way back to base. But nightly bombing soon began, and even though the darkness hampered much of the Luftwaffe’s accuracy, the result was still devastation, and a population forced to seek shelter and sleep far underground in Tube stations. It was, and remains, unimaginably relentless – in the following months, some 19,000 tons of bombs fell on London alone.
But with the coming of that ferocious onslaught to London, the cryptographers at Bletchley made a further breakthrough. Crucially, the Germans sent information about their bombers’ navigation beams – the beams that were supposed to keep them on course – via radio. These radio signals were picked up by the Y Services. And on being passed on to Bletchley, a new colour of Enigma decrypt – ‘Brown’, for this section of the Luftwaffe – was assigned to the specific cracking of such messages.
The operatives of Hut 6 rapidly succeeded in doing so. Within days the Air Ministry was receiving vital information concerning potential raids and the numbers of bombers that might be involved. Thanks to Enigma, as Oliver Lawn explains, the Air Ministry also had the wherewithal to ‘bend’ the German navigation beams, thereby causing the planes to drop their loads in the wrong places: ‘One of the things the Germans used the Enigma machine for, in the early stages of the war, was directing their bombing of British cities – beam bombing. That’s an aeroplane going along a beam and another beam being