In the air, the situation was just as confused. Night-fighter pilots who had been following instructions from their fighter-control officers now found themselves being sent round in circles. When it became clear that something was wrong with the ground radar, they began to rely on their Lichtenstein sets – but they, too, were beginning to show false readings, as one German fighter pilot, Wilhelm Johnen, recalled:

It was obvious that no one knew exactly where the enemy was or what his objective would be. An early recognition of the direction was essential so that the night fighters could be introduced as early as possible into the bomber stream. But the radio reports kept contradicting themselves. Now the enemy was over Amsterdam and then suddenly west of Brussels, and a moment later they were reported far out to sea in map square 25. What was to be done? The uncertainty of the ground stations was communicated to the crews … No one knew where the British were, but all the pilots were reporting pictures on their screens. I was no exception. At 15,000 feet my sparker announced the first enemy machine on his Li [airborne Lichtenstein radar set] … Facius proceeded to report three or four pictures on his screen. I hoped that I would have enough ammunition to deal with them! Then Facius suddenly shouted: ‘Tommy flying towards us at a great speed. Distance decreasing … 2000 yards, 1,500 … 1,000 … 500 … He’s gone.’ ‘You’re crackers, Facius,’ I said jestingly. But I soon lost my sense of humour, for this crazy performance was repeated a score of times. ¹⁶

No matter where the pilot flew he made no contact with any bombers: they disappeared, like phantoms, as soon as he approached. Window, it seemed, was having exactly the effect that the British desired.

* * *

As the leading British Pathfinder aircraft crossed the German coast near Heide, they began to drop the first of their yellow route-maker flares. The idea was to give the bomber stream, which was still spread out all over the sky, a single point to fly through – that way they would be a far more concentrated force as they arrived in Hamburg. However, it was not only the RAF bombers who saw the flares: a handful of German night fighters in the area spotted them too. In the absence of anything else to help them find the bomber stream, they headed towards the light. One managed to shoot down a Halifax, which fell in flames and exploded over the sea. A few minutes later a second Halifax was attacked, but this time the rear gunner returned fire at once, and the German plane fell, eventually crashing into the ground near Flensburg. ¹⁷

It is easy to summarize such events in a few words, but combat like this was a desperate affair, especially for British bomber crews. After more than two hours of silence, a burst of fire could appear from the darkness and kill seven men in an instant. Crews that were shot down rarely saw it coming. If they did, a short burst from one of the gunners was sometimes enough to scare off the enemy – an alert bomber crew could be just as deadly as the night fighters, as the combat over the German coast that night demonstrated. Usually it was the rear gunner, with his clear-vision panel at the back, who saw the danger first. He would broadcast a warning to the pilot on the intercom: ‘Fighter on the port quarter – corkscrew port!’ The temptation to turn away from an attacker was strong, but the trick for survival was to turn intohim so that he could not follow. Then, for the next thirty seconds or so, the bomber pilot would have to throw his aircraft about the sky, hoping that he had dropped out of his attacker’s line of sight. As long as he kept flying in a spiral motion then his enemy would not be able to keep his guns trained on him for more than an instant. A minute later the bomber would be back on course, with nothing to show for the experience but the mess of charts and instruments that had been thrown off the navigator’s desk, and the faint smell of fear in the aircraft.

That night there would be very few such incidents. Most of the German night fighters remained tied to their ‘boxes’, unable to locate the bomber stream amid the confusion. The aeroplanes continued unmolested across the coast, and down to their next turning point above Kellinghausen, a few minutes north-northwest of Hamburg.

Some of the crews dropped propaganda leaflets on German towns along the way. More would drop leaflets later, either over the target or on the way home. Leafleting was an unpopular pastime in the higher levels of Bomber Command, and staff officers joked that its only effect was to supplement German civilians’ rations of toilet paper. (They were only half joking: when middle-class Hamburg housewives were reduced to cutting squares of toilet paper from biscuit wrappers, this important commodity was in short supply.) ¹⁸Tonight’s leaflets showed a picture of RAF bombers flying over the burning streets of Dortmund, with the caption ‘ Die Festung Europa hat kein Dach’ (‘Fortress Europe has no roof’). To press the message home, one or two airmen emptied the contents of their urine bottles on to the leaflets before dropping them out – a petty act of contempt to add to the injuries they were about to inflict. ¹⁹

Eventually, after almost three hours in the air, the navigators of the leading Pathfinders recognized the outline of the city on their H ₂S sets: they had arrived. As they began their final approach to Hamburg, the crews of more than seven hundred bombers braced themselves for the onslaught of flak and searchlights they expected to encounter above the most heavily defended target in northern Germany. But the nightmare never materialized. There were fifty-four heavy and twenty-six light flak batteries defending the city, and twenty-two searchlight batteries, ²⁰but they were all reliant on the same ‘Würzburg’ radar sets that were being disrupted so efficiently by Window. In some cases the battery commanders could hear the drone of aeroplanes in the sky above them, yet when they turned to their radar operators for confirmation the response was the same as before: instead of clear, distinct pulses showing where the aircraft were, the radar screens were a mass of flashing zigzag curves, making it impossible to distinguish anything specific. Some batteries began to shoot random, unaimed barrages into the sky; others remained silent. Hamburg’s defences had been blinded.

For some of the more experienced bomber crews, the sight that greeted them when they arrived over the target was a dream come true. ‘Under normal circumstances the searchlights kept a fairly accurate pinpoint on any aircraft,’ says Leonard Cooper, a flight engineer with 7 Squadron (Pathfinder Force), ‘but on this occasion they were just waving around all over the place.’ ²¹Ted Edwards, a pilot from 100 Squadron, was equally impressed: ‘We were quite amazed to see the searchlights just weaving around the countryside over enemy territory. They hadn’t got a clue where we were.’ ²²

For those sceptics who had doubted that Window would work, it was a moment of revelation. ‘They said that Window was going to upset the German radar when we went in, but we more or less said, “Oh, yes?”’ remembers Leonard Bradfield, a bomb-aimer with 49 Squadron. ‘But when we actually got there it was happening! We were absolutely delighted.’ ²³He continues:

It was absolutely fantastic. We came up the Elbe and could see the river quite clearly. The radar-controlled blue master searchlights were standing absolutely upright and the white ones were weaving around, just searching. There were no night fighters because they were all in their boxes waiting to be given the vectors. The flak was just in a block over the target … It was the only time on any bomb run I was able to have 20 seconds completely unimpeded, without being stalked by the flak. ²⁴