The thousand-bomber raid on Cologne

On the night of 30/31 May 1942 the British bomber force, RAF Bomber Command, sent 1,047 aircraft to Cologne. No one had ever before sent so many bombers against a single target. The largest earlier RAF raids had numbered about 270 aircraft, and during the Blitz the Luftwaffe had sent at most a few hundred against any one city. The operation was code-named Millennium, and it went down in history as the first “thousand-bomber raid”. In about 90 minutes almost one and a half thousand tonnes of bombs, two-thirds of them incendiaries, fell on one of the largest cities of the Reich. Some 2,500 fires broke out, almost five hundred people were killed, and more than 45,000 were left homeless.

It is sometimes written that the raid “revealed new techniques of area bombing”. Bombing whole districts of cities was not in itself new at the time: Bomber Command had been doing it since February 1942, and in March and April it had burned Lübeck and Rostock. What was new was the scale of the raid and the way it was conducted. For the first time all the aircraft flew in a single concentrated “bomber stream”, along a common route, with assigned times and heights, and passed over the target in a time previously thought impossible. This method became the basis of Bomber Command’s operations until the end of the war.

A gamble for Bomber Command’s future

In the spring of 1942 the future of the British bomber force was by no means assured. The Butt Report of August 1941 had shown that only about a third of the crews who reported attacking dropped their bombs within five miles (eight kilometres) of the target. The Navy was demanding aircraft to fight the U-boats in the Battle of the Atlantic, the Army wanted air support, and the commanders in the Middle East and India wanted long-range bombers. Air Marshal Arthur Harris, who had commanded Bomber Command since 22 February, had about four hundred aircraft with ready crews available on any given day. Most were twin-engined Wellingtons, while the four-engined Stirlings, Halifaxes and Lancasters were only just entering service.

The raids on Lübeck and Rostock had shown that small, weakly defended old towns could be burned at night. The April raids on Cologne and Hamburg, however, though record-breaking, had produced scattered bombing and little damage. Harris needed something that would convince the War Cabinet that an expanded bomber fleet could deal Germany blows that no one else could. In mid-May he hit on the idea of gathering everything that could fly for a single night: not only the front-line squadrons but also the aircraft and instructors of the training units. The figure of a thousand was above all a symbol meant to capture the imagination of politicians and the public. The Chief of the Air Staff, Air Chief Marshal Charles Portal, backed the plan. According to Harris’s memoirs, Winston Churchill, to whom he presented it at his country residence, Chequers, agreed enthusiastically and declared that he was prepared to accept even the loss of a hundred aircraft.

The risk was enormous. Had the raid ended in disaster, Bomber Command would have lost not only front-line squadrons but also the instructors on whom the training of future intakes of aircrew depended.

Where to find a thousand aircraft

To muster a thousand machines, Harris drew on Bomber Command’s training groups – the Operational Training Units. Their aircraft were mostly older and worn out, and their crews consisted of instructors and the most advanced pupils, often before their first operational flight. More than three hundred machines, roughly one in three of those taking part in the raid, came from such units. About 250 aircraft had been promised by RAF Coastal Command, but a few days before the operation the Admiralty forbade their participation, judging that the propaganda effect did not justify diverting aircraft from the war against submarines. At the last minute Harris had to man several dozen more aircraft with pupils and instructors.

In the end 1,047 bombers took off: according to British operational records, 602 Wellingtons, 131 Halifaxes, 88 Stirlings, 79 Hampdens, 73 Lancasters, 46 Manchesters and 28 Whitleys. Among them were crews from the Polish bomber squadrons. No. 300 (Land of Masovia) Squadron sent 15 crews and No. 305 (Land of Greater Poland) Squadron 13; No. 301 (Land of Pomerania) Squadron also took part in the raid, and Polish airmen flew in aircraft of the training units as well. In addition, more than a hundred aircraft, mainly Blenheim light bombers, were to attack the airfields of German night fighters in the Netherlands and Belgium.

The bomber stream

Tactics were what mattered most. The German night defences were based on a belt of zones stretching from Denmark to France, known after its creator, General Josef Kammhuber, as the Kammhuber Line. In each zone radars on the ground guided one night fighter onto one bomber. The British calculated that the controller of a single zone could carry out at most about six interceptions an hour. Until then the bombers had flown over Germany singly, each on its own route, and a raid stretched over four hours or more, which gave the defences time to pick out their targets one after another. Now the whole armada was to pass through a few zones in a concentrated stream, so that the defences would be saturated and most of the bombers would get through before the fighters could react. Only 90 minutes were allowed over the target.

The price was the risk of collisions. Scientists of Bomber Command’s Operational Research Section estimated that there would be few collisions over the target and judged the risk acceptable compared with losses to fighters. Such a flight was made possible by the Gee radio navigation system, which allowed hundreds of aircraft to be led along a common route with sufficient accuracy to find a city. The March raids using Gee, however, had shown that the system failed over the smoke-shrouded Ruhr.

The target was originally to have been Hamburg, which lay beyond the range of Gee but on a clear night offered the chance of a great conflagration. For several days, however, the weather prevented take-off. On the morning of 30 May, with the full moon beginning to wane and the training groups unable to wait indefinitely, Harris, at his headquarters near High Wycombe, listened to the forecast: cloud was expected over northern Germany, while over the Rhineland the sky was to clear. He chose Cologne, the alternative target, which lay within range of Gee.

The plan of the raid was simple. The first fifteen minutes belonged to the experienced, Gee-equipped crews of Nos. 1 and 3 Groups, who were to mark the target with fires. Then the main mass would come over for an hour, and finally the heavy four-engined bombers of Nos. 4 and 5 Groups. Three aiming points were set: the old town by the Neumarkt square, and districts one and a half kilometres north and south of it. Before take-off the crews were read a message from Harris which, according to British studies, ended with the call to “let him have it – right on the chin”.

Over Cologne

The bombers took off from several dozen airfields in eastern England late on the evening of 30 May. The night was clear, and the moon lit up the Rhine and the spires of the cathedral, excellent landmarks. The first bombs fell on Cologne at 12.47 a.m. on 31 May. For the next hour and a half a bomber arrived over the city on average every few seconds. According to British records 868 aircraft bombed the main target, and a dozen or so others attacked alternative targets. 1,455 tonnes of bombs were dropped, roughly two-thirds of them incendiaries.

The German anti-aircraft guns fired throughout, and searchlights caught one aircraft after another, but the defences could not keep up. The crews of the last wave could see the burning city from a great distance as a glow on the horizon. Cologne’s fire brigade counted about 2,500 fires, of which it classed 1,700 as large. Wide streets and the efforts of the firemen prevented the fires from merging into a firestorm, but most of the destruction was caused by fire rather than by explosions.

One of the aircraft that did not return was a Manchester of No. 50 Squadron, piloted by the twenty-year-old Flying Officer Leslie Manser. Over Cologne the machine was caught by searchlights and hit by flak (PL). Manser dropped his bombs, nursed the burning, barely controllable aircraft out of the city and tried to reach England. Over Belgium, when the port engine caught fire and it became impossible to hold height, he ordered the crew to bail out and stayed at the controls himself. He refused the parachute that was handed to him. The aircraft crashed near Bree. One of the airmen was taken prisoner, but five evaded capture and returned to England, and their accounts led to Manser being awarded a posthumous Victoria Cross.

Losses

According to the report of Cologne’s police president, 469 people were killed, 411 civilians and 58 servicemen; later tallies, which include those who died of their wounds, give up to about 486 dead. 5,027 people were injured and 45,132 were left homeless. 13,010 dwellings were completely destroyed, 6,360 badly damaged and 22,270 lightly damaged. More than 3,300 non-residential buildings were burned out or destroyed, among them 9 hospitals, 17 churches, 16 schools, 4 university buildings and a dozen or so historic monuments. Factories and railway junctions were hit, but the only military installation damaged in the raid was an anti-aircraft barracks. British aerial photographs showed some 600 acres, or about 240 hectares, of built-up area destroyed. The cathedral, standing next to the main railway station, survived. In the following weeks, according to German studies, between 135,000 and 150,000 of the city’s roughly 700,000 inhabitants left; the number of registered residents fell by about 63,000.

Bomber Command lost 41 of the 1,047 aircraft sent to Cologne, or 3.9 per cent; counting the machines attacking the night-fighter airfields, 43 aircraft failed to return. The Germans claimed 44 shot down. About half of the losses occurred in the area of the city itself. According to British analyses, among the losses whose cause was established, those to anti-aircraft fire predominated; night fighters brought down only a few machines, and two bombers collided with each other. The commanders judged the losses moderate and a proof that the bomber stream worked.

Propaganda and reactions

On the morning of 31 May the raid became a sensation in Britain. The Air Ministry and the BBC announced that more than a thousand bombers had flown over Germany, and the newspapers vied with one another in their headlines. The Daily Express wrote of the greatest air undertaking attempted by any country in this war, and The Times headed its report “Reaping the Whirlwind”, an allusion to the biblical “they have sown the wind, and they shall reap the whirlwind”. Churchill wrote to Harris that this proof of the growing power of the British bomber force was the “herald of what Germany will receive, city by city, from now on”.

In Germany the reaction was twofold. The Wehrmacht communiqués played down the scale of the raid, and German radio presented it as the British answer to the defeat of their Soviet ally in the Second Battle of Kharkov and announced retaliation. The following night, 31 May/1 June, the Luftwaffe bombed Canterbury, opening the second phase of the Baedeker raids, which were far smaller than the raid on Cologne. According to the memoirs of Albert Speer, Hermann Göring refused to accept the reports of the Gauleiter of Cologne on the scale of the destruction and accused him of exaggerating. Joseph Goebbels admitted in his diary that the damage was heavy and feared the raid’s effect on the mood of the population.

Place in the war

Harris had won his gamble. The raid convinced the government that Bomber Command was an instrument worth investing in, and on 11 June 1942 its commander was knighted. The success, however, could not quickly be repeated. On the night of 1/2 June 956 aircraft, again including training machines, flew to Essen, but over the Ruhr, shrouded in haze and smoke, the bombs were scattered. On the night of 25/26 June about a thousand aircraft were sent to Bremen, this time with more than a hundred Coastal Command machines taking part, but once again cloud reduced the effectiveness of the attack. After that the great raids involving training units were abandoned, as they disrupted training too much. Further thousand-bomber raids came only in 1944, when Bomber Command could mount them with heavy front-line aircraft alone.

Operation Millennium nevertheless set the course for the rest of the war. The bomber stream, the concentration of a raid into a short time and the massed use of incendiaries became the foundation of Bomber Command’s operations. In August 1942 a target-marking force was formed, and new navigational aids and airborne radar improved accuracy. In the summer of 1943, in Hamburg, a firestorm caused by the raids killed about 34,000 people. Cologne was bombed more than two hundred times during the war; the heaviest raid, on the night of 28/29 June 1943, killed some 4,500 people. When the Americans entered the city in March 1945, they found a few tens of thousands of inhabitants and a sea of ruins, above which the damaged cathedral still stood. The area bombing of German cities, in which by various estimates several hundred thousand civilians died, remains to this day one of the most controversial decisions of the Allies, and the raid on Cologne of 30/31 May 1942 is its symbolic beginning.