Another problem was predictive flak. Using their radar screens, the German defenders could plot the height, speed and direction of flight of any one of the British bombers. They could then predict exactly where the aeroplane would be in the time it took the flak shells to fly 20,000 feet into the air, and direct the flak batteries accordingly. The only way for a British pilot to avoid this was to zigzag and corkscrew across the sky – which, when the sky was full of other aeroplanes, greatly increased the chances of a collision. When a crew were about to release their bombs even this course of evasive action was denied them: if they were to hit the target they were obliged to fly straight and level for a full minute before the bombs were released and they could think about escaping. Only when the photoflash had gone, marking the place they had bombed on an intelligence photograph, could they turn tail and head away from the hail of flak.

Hamburg had some of the most formidable flak defences in Germany. Not only was there a ring of batteries on the outskirts of the city, but four massive gun towers stood in the centre and the port. The heaviest guns were capable of firing a pair of 128mm shells twice a minute, each weighing 26 kilograms, to a range of 45,000 feet vertically into the sky. ⁵If an aircraft received a direct hit from a shell like this it spelled disaster for the crew inside – if not immediately, then during the long flight over the North Sea on the way home. Even if an aircraft was not hit, the threat of the incredible firepower exploding around them could seriously unnerve a crew, and cause them to drop their bombs early and off-target.

Given the importance of the target and the strength of Hamburg’s defences, Harris was determined to use every advantage he could to make sure the operation succeeded. By the summer of 1943 Germany’s radar-controlled defences were causing intolerable casualties, so Harris began to press the Prime Minister to authorize the use of a new secret weapon that would jam German radar. Codenamed ‘Window’, it consisted of bundles of paper strips coated with metal foil on one side. When the bundles were dropped down the flare chute during the flight over Germany they would disperse, and as the strips floated to earth they created a false ‘blip’ on German radar screens. With thousands of false readings it would become impossible for the operators to tell where the real bombers were – at a stroke, all of their defences would be rendered useless.

Until now the device had never been used because the Ministry for Home Security was terrified that Germany would copy it and use it against Britain. However, by 1943 the threat of a new Blitz by the Luftwaffe was unlikely, so on 15 July Churchill gave Harris the go-ahead. Ironically, the Germans already knew of the principle behind Window – their own version was called Düppel – but the German Chief of Air Signals, General Martini, had prevented its use because, he, too, was afraid of the consequences if the British ever copied the idea. ⁶Over the coming week Martini’s worst fears would come true.

Since Window only worked on the Würzburg and Lichtenstein frequencies, the bombers would also use two other devices: ‘Mandrel’, which interfered with the German long-range Freya radar, and ‘Tinsel’, which jammed German radio frequencies by transmitting the sound of the aircraft engines to drown the voices of the pilots and their radar controllers.

This, then, was the British plan of attack for what would become known as the battle of Hamburg. As Harris made his way back to his office, his deputy, Air Vice Marshal Sir Robert Saundby, remained in the Operations Room to organize the practicalities of the raid. First he telephoned Air Vice Marshal Don Bennett, head of the Pathfinder Force, which would lead the operation. After discussing the precise route to and from the target with him, Saundby set about organizing the other details of the attack: bomb loads, take-off times, aiming points and so on. Only after every detail had been precisely established would he and the rest of the staff retire to their own offices in the base at High Wycombe. For the rest of the day, department by department, the devastation of Hamburg was carefully prepared.

9. The First Strike

I know death hath ten thousand several doors

For men to take their exits

John Webster, The Duchess of Malfi ¹

At air bases across the eastern half of England it was a beautiful summer’s day. Clear blue skies and bright sunshine had brought most of the young men from their quarters early, and for the first few hours of the day they passed the time in whatever way suited them best: reading, sharing cigarettes outside their quarters, or playing cricket on the wide-open spaces of the aerodrome. There was an atmosphere of expectancy in the air: operations had been cancelled for two days in a row, and if they were cancelled again there would be the chance of a day out in one of the local market towns. They could dash for the bus to York or Nottingham, Lincoln or Cambridge or even take a train to London. They might perhaps catch a matinée at the cinema, then have a quick meal before they joined the many other servicemen at one of the pubs or Saturday-night dance-halls. For those with wives or girlfriends, it would be a chance to spend valuable time together; for those without, it would be an opportunity to meet some of the local girls. Unlike those in the other armed services, the men in Bomber Command were not quite so restricted by the discipline of barrack duties, and when they were not on operations their time was generally their own. It was a good life for a young man – as long as he remained on the ground.

The cancellation of the previous two operations, both on Hamburg, had been frustrating for everyone. Thursday had been particularly bad. Many crews had taken their aeroplanes to the end of the runways and were about to take off when the trip had been cancelled. Some had already swallowed caffeine pills or benzedrine, dispensed by the station medical officer, to keep them awake during the long flight across the North Sea and back. It was too late to get to any of the local towns to blow off steam, so those who could had made their way to the village pubs to counteract the action of the drugs in their system with alcohol. Others settled down in the mess, or tried to get an early night. Even those who hadn’t taken the MO’s ‘wakey-wakey’ pills often found it difficult to sleep. Having geared themselves up for action throughout the day, they found it difficult to let go of all the accumulated anxiety. They knew that any cancellation of operations was only a temporary reprieve: if they didn’t fly on their first, tenth or twentieth operation tonight they would only have to do it tomorrow or the day after.

While most of the young airmen relaxed in the morning sunshine, a few, usually the skippers of the aircraft, would make their way to the station office to hear the results of the morning’s ‘group tie-up’ with Bomber Command Headquarters. Others would go to the messes, where the battle order was pinned to a board whenever operations were on. When they discovered that ‘ops’ were indeed on, there was a general sigh. There was no indication of what the target would be, but the fuel loads designated for each plane were the same as yesterday so it was probably Hamburg again. There would be no chance of a trip to Betty’s Bar, or the Snakepit, or the Windmill Theatre this Saturday night. Reluctantly, they headed back out on to the airfield to relay the news to their air crews on the grass.

Once a crew knew that ops were on, a change came over them: the frivolity of a cricket match would be replaced with an air of purpose – they had a job to prepare for. They would leave off what they had been doing and make their way out to where their planes were standing, round the perimeter of the airfield. Here, trains of bombs would be arriving, ready to be fused by the station armourers, then loaded into the planes. That morning something else was waiting for them too: stacks and stacks of brown-paper parcels, piled up on the runway beside each plane. Many of the men were used to taking propaganda leaflets on a raid, but this was different. Unable to contain their curiosity some of the men opened the packages, but what they found inside perplexed them. Each package contained nothing but bundles of paper strips – about fourteen inches long and an inch wide – silver on one side, black on the other. Speculation about what they might be was rife. ‘We couldn’t make head nor tail of it,’ said Harold McLean, of 427 Squadron. ‘One chap peed on it to see if it reacted. It didn’t.’ ²