When Western Allied leaders met at the Casablanca Conference (January 14–24, 1943) the Combined Chiefs of Staff agreed that the USAAF and the RAF should coordinate bombing of Germany. The USAAF agreed to bomb by day—the preferred method of those who still believed in precision bombing —while RAF Bomber Command conducted area bombing by night. The directive for the CBO combined all threads of thinking about the functions of strategic bombing: destruction of enemy transportation and communications nets, retardation of war production, and conscious and deliberate suppression of civilian morale. Within the overall strategic directive given to the Western Allied air forces was a list of “primary objectives.” Listed by priority, these were: U-boat pens, the German aircraft industry, transportation and communications targets, synthetic oil facilities, and oil fields. The “Casablanca Directive” gave the CBO more apparent coherence than bombing yet displayed in fact, or was capable of achieving. Tensions persisted between airmen intent on using morale bombing as a supposed war-winning weapon and those who saw bombing’s major contribution to the war as wrecking critical areas of enemy production and preparing the way for a ground invasion through carefully targeted tactical strikes. Arthur Harris of RAF Bomber Command reinterpreted the Directive in ways that allowed him to continue to conduct the morale bombing he preferred. Though not as baldly, USAAF chiefs similarly interpreted the Directive to fit what they were already doing.
Harris launched a series of “air battles” during 1943, which he argued would prove decisive. The first was fought in the smog-filled skies above the Ruhr Valley, starting on March 5. Over the next four months bombers pounded Ruhr cities and industries, taking heavy casualties over the most heavily defended territory in Germany. Nuremberg, Essen, Dortmund, Duisburg, and Düsseldorf were all attacked multiple times. Bochum, Oberhausen, and smaller cities were also hit. Over 1,000 Allied aircraft were lost in the Ruhr campaign. While heavy damage was done and much loss of German life incurred, the Ruhr continued to produce critical resources for the German war economy. Harris ordered bombing of other German cities, including Cologne. A series of four great raids (GOMORRAH) by 3,000 heavy bombers of RAF Bomber Command carried out from July 24 to August 2, 1943, destroyed half of Hamburg. The raids created a firestorm that burned out hundreds of war factories and killed thousands of workers, while “de-housing” many thousands more. That set back German war production in Hamburg, making the argument over targeting doctrine even more complicated.
At the first Québec Conference (August 17–24, 1943), official emphasis on morale bombing was dropped in favor of attacking clearly listed, high-value targets. Among these, the highest priority was given to smashing the Luftwaffe’s fighter force and slowing fighter production by bombing aircraft factories. In fact, such priority targeting had been undertaken since May. But in accordance with the Québec directive, U.S. 8th Air Force attempted two precision raids on the critical and heavily defended fighter and ball-bearing works at Schweinfurt, with a companion raid against Regensburg. Carried out on August 17 and October 14, 1943, the Schweinfurt raids were a turning point in the air war. Out of 376 American bombers that made the first raid, 147 never saw their home airfields again. The second raid was even more disastrous: 60 bombers were shot down and 142 badly damaged out of a force of 291. The Americans did not try to hit Schweinfurt again until February 1944. The focus of Bomber Command turned to the Berlin bomber offensive through the winter of 1943–1944, while the USAAF reconsidered the wisdom of its entire approach to bombing Germany.
The official 1944 focus on reducing German fighter production and luring existing fighters into battle to be destroyed before the OVERLORD campaign was made possible by the advent of long-range American fighters. P-51 Mustangs equipped with drop tanks capable of escorting bombers deep into Germany turned the air war decisively and permanently in favor of the Western Allies. Rising confidence and air dominance led to the “Big Week” operation, a massive six-day bombing campaign (February 20–25, 1944) code named ARGUMENT. It was carried out by the U.S. 8th, 9th, and 15th Army Air Forces based in Britain and Italy and by RAF Bomber Command. Over 6,150 bombers were involved in a week-long assault on Luftwaffe fighter factories and bases. The Western Allies lost 411 aircraft, including several dozen fighters. It is believed that “Big Week” seriously interrupted fighter manufacture for several months, although production did not begin terminal decline until September. “Big Week” certainly damaged Luftwaffe morale, which was already low from chronic attrition and persistent failure to stop the bombers. This phase of the CBO was crucially important. It severely attrited Luftwaffe pilots and thereby established air supremacy over the landing zones in France in time for the invasion of Normandy in June. The air battle over Germany also eliminated many experienced Luftwaffe pilots. Thereafter, German fighter pilot skills were noticeably lessened and Western Allied kill ratios climbed. With long-range escort fighters available by mid-1944, even Bomber Command began carrying out more daylight precision raids. Fighter attrition continued over Germany during the last months of 1944 and into 1945, when the hugely controversial— though operationally not distinctive— Dresden raid was carried out, among other city bombings.
Suggested Reading: Tami Biddle, Rhetoric and Reality in Air Warfare: The Evolution of British and American Ideas about Strategic Bombing, 1914–1945 (2002).