The Battle of the Ruhr begins

During the night of 5–6 March 1943, 442 aircraft of RAF Bomber Command attacked Essen, home of the Krupp armaments works. For the first time, a major raid on the heart of the Ruhr was marked entirely blind by aircraft guided by radio from England using the Oboe system. The attack opened a series of several dozen heavy raids on the industrial cities of the Rhine and the Ruhr that lasted until July 1943. The British called it the Battle of the Ruhr. It was the first campaign in which the head of Bomber Command, Air Marshal Arthur Harris, was able to use on a large scale the methods and equipment that had been in preparation since 1942.

In the same days Bomber Command also struck at two cities in southern Germany that lay beyond the range of Oboe. Chronologies of events record that Nuremberg was heavily bombed on 8 March and Munich on 9 March. More precisely, these were night raids, on the nights of 8–9 and 9–10 March. Both belonged to the same offensive, and their course shows clearly what a great difference radio target-marking made at the time.

The Ruhr before March 1943

The Ruhr was the industrial heart of the Reich. An area of some 2,600 square kilometres between Duisburg and Dortmund was home to more than four million people, and its mines, coking plants, steelworks and factories produced most of Germany’s coking coal and steel. RAF bombers had been attacking it since May 1940, but for almost three years with meagre results. An industrial haze hung almost permanently over the Ruhr valley, obscuring targets even on clear nights. Crews searching for Essen dropped their bombs on neighbouring towns or in open fields. In 1941, moreover, Krupp had built a decoy of its works on the Rottberg hill near Velbert, lit so as to resemble a poorly blacked-out industrial plant, and for a time it drew some of the bombs.

Even new navigational aids did not change this picture. The Gee system, introduced in the spring of 1942, allowed bombers to reach the Ruhr but was not accurate enough to hit a particular city, and the first Gee raids on Essen failed. The thousand-bomber raid on Essen in June 1942 likewise scattered in cloud and mist, and the Krupp works came through it almost unscathed. By British reckoning, over the whole of 1942 Bomber Command sent some 3,700 aircraft against Essen and lost more than two hundred of them without achieving anything that justified the effort.

Harris’s new tools

In the winter of 1942–1943 Bomber Command’s situation changed in several respects at once. First, the command received a clear political mandate. At the Casablanca Conference the Combined Chiefs of Staff agreed on a joint Anglo-American bomber offensive, and the directive of 21 January 1943, passed to Harris at the beginning of February, set as its aim “the progressive destruction and dislocation of the German military, industrial and economic system, and the undermining of the morale of the German people”. Harris read it as approval for continuing the area attacks on German cities that he had been carrying out since the spring of 1942. The Chief of the Air Staff, Air Chief Marshal Charles Portal, supported this campaign.

Second, the bomber force itself had changed. Light and medium twin-engined bombers had disappeared from the front line, and an ever larger share of the force consisted of four-engined Avro Lancasters and Handley Page Halifaxes, able to carry several tons of bombs. Alongside them still flew Short Stirlings and twin-engined Vickers Wellingtons. According to the British official history, in February 1943 Harris had on average just under 600 aircraft with crews ready to fly, but they were far more powerful machines than a year earlier.

Third, Bomber Command at last had the means to find its targets. In August 1942 the Pathfinder Force was formed under the Australian Donald Bennett, becoming No. 8 Group in January 1943. Its experienced crews flew ahead of the main force and marked the target. From the night of 16–17 January 1943 they used special target indicator bombs for this purpose, which at a set altitude ejected coloured pyrotechnic candles that burned on the ground as bright patches of fire or hung on parachutes above the clouds. At the end of January the H2S airborne radar, which showed the outline of the terrain beneath the aircraft, came into service, and in February it brought its first success over Wilhelmshaven.

Most important for the Ruhr, however, was Oboe. Two ground stations in England, known as “Cat” and “Mouse”, used radio pulses to measure the aircraft’s distance from them. The first guided it along an arc over the target, the second indicated the moment of release. The accuracy was within a few hundred metres, regardless of cloud and haze. Because the waves do not follow the curvature of the Earth, the range depended on the aircraft’s altitude. An aircraft at 8,500 metres could receive the signals at a distance of about 430 kilometres – just enough to cover the Ruhr, but not Berlin or Bavaria. Oboe was therefore fitted to the fast, high-flying Mosquitoes of No. 109 Squadron. It was first used operationally during the night of 20–21 December 1942 against a power station at Lutterade in the Netherlands. The system also had weaknesses: a pair of stations could handle only one aircraft at a time, and each approach took about ten minutes, so the markers went down intermittently and had to be kept going with ordinary target indicators.

The raid on Essen

On the evening of 5 March, 157 Lancasters, 131 Wellingtons, 94 Halifaxes, 52 Stirlings and eight Oboe Mosquitoes set out for Essen. According to Bomber Command records, that night the command flew its 100,000th operational sortie since the start of the war. Not everything went to plan: 56 aircraft turned back before reaching the target because of technical faults and other reasons, including three of the eight Mosquitoes on which the success of the raid depended. The remaining five, however, arrived over Essen on time, at around 9 p.m., and marked the city centre very accurately. The Pathfinder crews kept the marking going with further target indicators. Because the entire marking was done blind, the haze over Essen did not matter this time.

The main force bombed in three waves: first the Halifaxes, then the Wellingtons and Stirlings, and finally the Lancasters. Two-thirds of the tonnage consisted of incendiary bombs, and a third of the high-explosive bombs were fitted with long-delay fuses to hamper rescue work and firefighting. The attack lasted about 40 minutes. 362 crews reported bombing the target, dropping more than 1,000 tons of bombs. This pattern – Oboe marking, backed up by the Pathfinders, followed by a concentrated attack in waves by the main force with a preponderance of incendiaries – became the model for most of the raids on the Ruhr in the months that followed.

British reconnaissance photographs showed some 65 hectares of buildings destroyed in the centre of Essen and hits on 53 buildings of the Krupp works. According to German figures compiled in Essen, at least 457 people were killed and more than 3,000 buildings were completely destroyed. Stray bombs fell on six other towns in the Ruhr. Bomber Command lost 14 aircraft – four Lancasters and four Wellingtons, and three Halifaxes and three Stirlings – or 3.2 per cent of those dispatched. At Bomber Command headquarters the raid was regarded as the first real success over a city that had defied the crews for years.

A week later, during the night of 12–13 March, 457 aircraft returned to Essen. The centre of the bombing fell squarely on the vast Krupp works west of the city centre. According to British photographic assessment, the factory suffered 30 per cent more damage than a week earlier. This time, however, the defences were more alert: 23 bombers, 5 per cent of the force, were shot down. According to the New Zealand official history, after the second March raid Krupp did not resume locomotive production.

Nuremberg and Munich

Not all the March targets lay within Oboe range. During the night of 8–9 March, 335 bombers – 170 Lancasters, 103 Halifaxes and 62 Stirlings – flew to Nuremberg, the city of the NSDAP party rallies and an important centre of the electrical and engineering industries. It was the second raid on the city in two weeks, after the attack of 25–26 February. At this distance the Pathfinders had to mark the target by H2S radar and visually. There was no moon, and although the sky was cloudless, haze made it impossible to identify the city accurately. According to Bomber Command records, the markers and bombs were spread over more than 16 kilometres along the line of approach, and more than half the bombs fell outside the city limits of Nuremberg. Even so, the city suffered serious damage. According to official German figures, 343 people were killed and some 600 buildings completely destroyed, and among the places damaged were the MAN and Siemens works and the marshalling yard. Bombs also fell on neighbouring Fürth, where, according to local sources, between 32 and 40 people were killed. The RAF lost eight aircraft, 2.4 per cent of the force.

The following night, 9–10 March, 264 bombers – 142 Lancasters, 81 Halifaxes and 41 Stirlings – attacked Munich, the “Capital of the Movement” of National Socialism. It was the first raid on the city to use H2S radar. The wind pushed the bombing onto the western part of the city rather than the centre, but the damage was heavy nonetheless. The worst hit were the BMW works, where the aero-engine assembly shop was out of production for six weeks. Many other plants were also destroyed, including 141 small workshops. Studies of Munich state that more than 200 people were killed in the raid and several hundred injured. Bomber Command lost eight aircraft, 3 per cent of those dispatched.

These two raids showed the limits of what was then possible. Beyond the range of Oboe, bombing was still scattered and dependent on the weather, and the bombs fell on residential districts and suburbs more often than on factories. The raid by 314 aircraft on Stuttgart during the night of 11–12 March failed in a similar way: most of the bombs fell on fields and suburbs, and the Germans used dummy target indicators for the first time to deceive the crews. Harris therefore concentrated his main effort in the spring of 1943 on the Ruhr, where Oboe gave him the advantage, and sent forces against more distant targets only from time to time, so that the Germans could not concentrate all their defences over the Ruhr.

Place in the war

The raid of 5–6 March opened Bomber Command’s first great planned campaign. By July 1943 the bombers had struck the Ruhr and the neighbouring Rhineland 43 times over 39 nights, attacking Duisburg, Dortmund, Bochum, Düsseldorf, Krefeld, Wuppertal and Cologne, among others, as well as Essen many times over. The offensive peaked in May and June. During the night of 16–17 May the Lancasters of No. 617 Squadron destroyed the Möhne and Eder dams in Operation Chastise, and at the end of May a raid on Wuppertal started a fire in which several thousand people died. With bitter irony the crews called the Ruhr valley “Happy Valley”, because it was defended by a dense belt of searchlights, anti-aircraft guns and night fighters.

According to the British official history, over the whole battle Bomber Command dispatched 18,506 aircraft, of which 872 failed to return and 2,126 were damaged. The command could not have sustained such heavy losses for long. On the German side some 15,000 people are estimated to have been killed – city dwellers and forced labourers from occupied Europe. The assessment of the results remains disputed. The German historian Horst Boog believed that Bomber Command had overestimated the importance of Essen and that Ruhr industry had lost only a few weeks’ production in all. The British historian Adam Tooze, by contrast, sees the Battle of the Ruhr as a turning point for the German war economy: shortages of steel and components from the Ruhr halted, in the second half of 1943, the growth in armaments output that the Armaments Minister, Albert Speer, had been achieving since 1942.

The offensive also forced changes on the German side. The Luftwaffe drew into the defence of the Reich ever more fighters and anti-aircraft guns that were needed on the Eastern Front and in the Mediterranean, and industry began to disperse its production. At the end of July 1943 Harris shifted his main effort to Hamburg, where Operation Gomorrah caused a firestorm, and from November to Berlin. At the same time, from the spring of 1943, an ever greater role was played by the American day bombers, which in January had attacked Germany for the first time. March 1943 was thus the moment when the RAF’s night raids ceased to be largely haphazard and became a tool capable of systematically destroying designated cities – with all the burden that this placed on the civilian population.