The Battle of the Ruhr (5 March – 31 July 1943) was a strategic bombing campaign against the Ruhr Area in Nazi Germany carried out by RAF Bomber Command during the Second World War. The Ruhr was the main centre of German heavy industry with coke plants, steelworks, armaments factories and ten synthetic oil plants. The British attacked 26 targets identified in the Combined Bomber Offensive. Targets included the Krupp armament works (Essen), the Nordstern synthetic oil plant at Gelsenkirchen and the Rheinmetal–Borsig plant in Düsseldorf, which was evacuated during the battle. The battle included cities such as Cologne not in the Ruhr proper but which were in the larger Rhine-Ruhr region and considered part of the Ruhr industrial complex. Some targets were not sites of heavy industry but part of the production and movement of materiel.
The Ruhr had been attacked by Bomber Command from 1940; its defences and the amounts of industrial pollutants produced a semi-permanent smog that hampered bomb aiming. Along with anti-aircraft guns, searchlights and night fighters, the Germans built large night-time decoys such as the Krupp decoy site () near Essen to spoof the bombers into hitting the open country. Cities outside the Ruhr were attacked to prevent the Germans from concentrating their defences and before the end of the battle, Operation Gomorrah on 24 July 1943 began the Battle of Hamburg. After the turn to Hamburg, Bomber Command continued to raid the Ruhr to keep the German defences dispersed.
Background
Bomber Command, 1942
In 1942 some answers to the chronic problems of night navigation and target finding began to emerge but the number of bombers had stagnated. In November 1941 Bomber Command had a daily average of 506 bombers available and in January 1943 the average was 515. To carry out the Thousand-bomber raids Bomber Command drew on crews and aircraft from the Operational Training Units, which could only be exceptional. Navigation had been helped by the introduction of Gee but this device lacked accuracy for bombing through the dark and smog of the Ruhr, lacked range and from 4 August 1942 the Germans began to jam the device.
The Pathfinder Force (PFF) was established on 15 August 1942 but with Gee jammed and no target indicator bombs to mark the aiming point for the rest of the bombers (the Main Force), the task of the PFF varied from thankless to impossible. Despite its problems, Bomber Command had been able to achieve some spectacular results but these had been isolated events and due to favourable circumstances as well as judgement. The loss of 1,404 aircraft and 2,724 damaged to German night defences of increasing quantity and quality, especially German night fighters () had become a serious threat to the viability of the command and of strategic bombing as a theory of war.
In 1942 Bomber Command had created 19 new squadrons but 13 had been transferred to other commands. The quantity of aircraft had barely increased but a big improvement in quality had been achieved. Bristol Blenheim light bombers and Armstrong Whitworth Whitley medium bombers had been retired from the command in mid-1942, followed by the Handley Page Hampden medium bomber in September. The disappointments of the Short Stirling and the early Handley Page Halifax variants and the fiasco of the Avro Manchester, withdrawn in June 1942, was balanced by the Avro Lancaster, which made its operational début in March and demonstrated its superiority over all other bombers. Re-equipment with new types of aircraft led to an average of 16.36 per cent of Bomber Command squadrons withdrawn from operations for conversion onto new aircraft in 1942, against 3.3 per cent in 1943. On 1 January 1942 the command had 48 squadrons, 9 with heavy bombers, 34 with medium and five with light bombers (Blenheims). On 1 January 1943, there were 49 squadrons, 32 heavy, 11 medium and six light (de Havilland Mosquito). The command had flown 30,508 operational sorties in 1941 and dropped of bombs, in 1942 it dropped from 29,929 sorties.