Over those seaside towns all the separate squadrons in each group would merge into a wide stream heading out to sea. For those in the vanguard it was possible to make out many of the other aircraft filling the sky around them. By now it was well after ten o’clock, but with double summertime bringing the clocks forward two hours the sky was still fairly light, especially to the north and west. For those coming later it was already too dark to make out any of their fellow aeroplanes. Only the occasional blink of green and red navigation lights told them that they were not alone, but as they headed out to sea even those lights were extinguished, rendering almost eight hundred aircraft virtually invisible in the night.

As they made for the darkness of mainland Europe, the atmosphere inside each aeroplane was professional, businesslike. Each member of the crew was left to perform his duties in his own way. In general, strict radio silence was observed, and crews did not speak to each other on the intercoms unless there was something important to report. The only sound was the constant drone of the aircraft engines as they continued to climb as high as they could go, but in the thin, warm air of summer many aeroplanes struggled to reach their operational ceilings.

Leading the bomber stream were the Pathfinders of 8 Group. Behind them, spreading back over almost two hundred miles, was the rest of the force. They were heading to a point about eighty miles from the German coast – 54°45N, 07°00E – where the three separate streams of bombers were to merge into one, then turn towards the south-east and their target. The lead aircraft had already been in the air for two and a half hours. They turned at about twenty past midnight and headed towards the German coast on a bearing of 103°.

Ten minutes later the flight engineer in each of the leading aircraft climbed over the main spar into the back of the plane and began to drop the first bundles of Window. ¹⁰The crews had been provided with stop watches and told to throw the bundles down the flare chute at exactly one-minute intervals. The bundles were supposed to disperse into small clouds of paper that would float harmlessly down through the air. In practice, however, the ‘machine-like’ efficiency called for at the briefing often ended up being a little more chaotic. Sometimes the Window would blow back into the aircraft, filling the air in the back of the plane with metallized paper strips. Once or twice the bundles did not open properly and the solid packets hit other bombers, ripping off aerials or even breaking through the Perspex of a gun turret. ¹¹Even when the Window dispersed properly, it often blew up on to the mid-upper turrets of the aeroplanes, obscuring the gunner’s view. One side of the paper was covered with a black coating that easily rubbed off, and after fifteen minutes or so the plexiglass on the mid-upper turret was so smudged and blackened that the gunner there was effectively blinded. The black coating also came off on the man tasked with throwing it from the plane; many bombaimers and flight engineers soon looked like chimney sweeps, covered from head to toe with soot.

Despite the various mishaps, though, most of the crews managed to drop the bundles of metal strips according to plan. As they ploughed on towards the German coast they had no idea whether or not the new device would work, and gradually they became anxious once more. In less than half an hour they would be over Hamburg, and the real test of their new tactics would begin.

* * *

By now the Germans knew the RAF were coming. A long-range Freya radar station near Ostend had picked up the first aeroplanes heading across the sea at around eleven o’clock, and the defences had been plotting the course of the bomber stream ever since, waiting to see where it turned before committing their night fighters to action. ¹²By half past midnight, shortly after the first planes in the bomber stream had turned towards Hamburg, the night fighters of several airfields were airborne. Since Hamburg was now a possible target, at 12.33 a.m. the order was given to sound the Fliegeralarm sirens. ¹³

In 1943 Germany had the most impressive defences of any country in the world. First came the infamous Kammhuber Line – a belt of interlinked night-fighter ‘boxes’ that stretched the length of the European coast. Each box had its own fighters, which would patrol that box only, ensuring an evenly spread defence across the whole line. Hamburg in particular was protected by more than a dozen airfields. ¹⁴Closer in, there were belts of searchlights, and dozens of heavy-flak batteries (see Map 1, p. 36). It was a formidable set-up, and the whole structure was now on high alert, waiting for the British to arrive.

As the bomber stream approached the coast, it was being watched closely by the head of the German 2nd Fighter Division, Generalleutnant Schwabedissen, in his headquarters at Stade airfield. Housed in a giant bomb-proof bunker, Schwabedissen’s central combat station was the nerve-centre of all the defences in north-west Europe and was a true triumph of German technology. One of only five control centres in the country, it was nicknamed the ‘Battle Opera House’, or the ‘Kammhuber Kino’, because of its resemblance to a cinema. Inside, dominating the huge control room, there was a gigantic frosted-glass screen, about fifty feet wide, inscribed with a map of Germany. On to it were projected spots of light, which represented all of the different aeroplanes in the sky at any one time – white spots to show the enemy planes approaching, green spots for the German night fighters, and illuminated details of their height, position and direction of flight.

Even the Luftwaffe’s commander of fighters, Adolf Galland, found this feat of technology impressive:

The whole was reminiscent of a huge aquarium lit up, with a multitude of water-fleas scuttling madly behind the glass walls. Each single dot and each change to be seen here was the result of reports and observations from radar sets, aircraft-spotters, listening posts, reconnaissance and contact planes, or from units in action. They all merged together by telephone or wireless in this centre, to be received, sorted, and within a few minutes transposed into transmittable messages. What was represented here on a giant map was a picture of the air situation … with about one minute’s delay. ¹⁵

In front of this huge map, on rising steps like those in an amphitheatre, fighter-control officers ( Jägerleitoffiziere) were seated in several rows, ready to direct their night fighters by radio into the hunt. Above them, on a raised balcony, Generalleutnant Schwabedissen and his staff conducted the battle against the Allied bombers in an unhealthy fog of cigarette smoke, his voiced orders rising above a symphony of ticking teleprinters, humming ventilators and the urgent murmur of telephone operators across the room.

Tonight everyone was watching the screen as avidly as any cinema audience. Schwabedissen had already ordered his night fighters to scramble, and scores of green T-shapes were making their way across the frosted-glass map. Ahead a mass of white dots was making its way towards the German coastline. But something was wrong: while the front of the bomber stream still appeared to be moving forwards, the tail end remained static on the map – it was as if the RAF bomber force was expanding before their eyes.

Up on the balcony, Schwabedissen demanded to know what was going on, but nobody could give him a straight answer. Nervous telephone operators were engaged in urgent conversations with radar stations throughout north-west Germany. The messages they were getting back were always the same. It was impossible: there appeared to be not merely hundreds of bombers approaching but thousands– too many for the radar screens to cope with. Some radar sets appeared to have stopped working altogether: instead of registering single, distinct ‘blips’ on their screens they showed nothing but a general fuzz, as if the bombers were approaching in a solid wall several miles wide.