Strategic bombing may generally be defined as air attacks directed at targets or systems capable of having a major impact on the will or ability of an enemy nation to wage war. Airpower proponents have touted strategic bombing as a unique war-winning capability and have used it to justify independent air services.
When World War II began, only two nations had a coherent and committed strategic bombing program: Great Britain and the United States. Although most states with advanced militaries had interest in powerful airpower, continental concerns, resource limitations, or misguided procurement policies hindered most aspirants to powerful long-range bombing forces. Only relatively protected naval powers such as the United States and Britain could afford to focus so much attention on strategic bombing, lured by the strong political appeal of its promise of quick victory at relatively low cost. Both efforts had roots in the experience of the Royal Air Force (RAF) in World War I, when Sir Hugh Trenchard developed tactics and policies for the world’s first independent air service and when talented subordinates such as Hardinge Goulburn Giffard, 1st Viscount Tiverton (subsequently 2nd Earl of Halsbury) pioneered target analysis for morale and material effects to assault the foundations of the German war economy. Although airmen in both countries became aware of the ideas of Giulio Douhet during the interwar years and used them to support arguments for strategic airpower, Douhet had little impact on the evolution of the RAF or the U.S. Army Air Corps.
The RAF continued to pursue Trenchard’s ideal of a massive aerial offensive, assisted by politicians who were willing to fund an aerial deterrent instead of large expensive land armies that could become involved in more bloody continental wars. However, targeting priorities remained vague, and the war would soon reveal the large gap between claims and capabilities.
The Americans took a different approach that can be traced back to Tiverton’s precedents. Although the subordinate army air service’s primary mission remained ground support, a group of smart young officers at the Air Corps Tactical School (ACTS) developed a theory of precision daylight bombing of carefully selected targets in the industrial and service systems of enemy economies. Pinning their hopes on the capabilities of new aircraft such as the B-17 Flying Fortress, these airmen expected unescorted self-defending bombers to destroy vital nodes of the enemy’s war economy that would grind it to a halt.
Bombing examples before and during the early days of World War II—in Spain and China and even the German Blitz on London—appeared to demonstrate the ineffectiveness and drawbacks of indiscriminate attacks on cities and to support the superiority of precision tactics. When President Franklin D. Roosevelt asked the army and navy for munitions estimates for a potential war in 1941, many of those ACTS instructors had joined the Air Staff in Washington. They soon developed a plan called AWPD/1 that envisioned a precision bombing campaign as a key component of the American war effort. When a larger plan that included AWPD/1 was accepted, the U.S. Army Air Forces (USAAF) finally had a justification for pursuing its own independent strategic bombing. They also found it difficult to put theory into practice.
Early British attacks moved from a Tivertonian focus on key systems like power plants or oil to a more Trenchardian reliance on widespread morale effects. Daylight raids proved deadly for RAF Bomber Command, revealing critical deficiencies in the number and quality of their bombers. Operations shifted to the nighttime, but the August 1941 Butt Report concluded that only about one in five aircrews were bombing within five miles of their intended targets. Adapting to the reality of their capabilities, in February 1942 Bomber Command was directed to attack area targets—that is, cities—with the objective of undermining German civilian morale, particularly that of industrial workers. Under the direction of Air Chief Marshal Sir Arthur Harris, Bomber Command built up its strength and obtained better aircraft, especially Halifax and Lancaster four-engine bombers. On 30 May 1942, Bomber Command mounted the first “thousand bomber raid” on Cologne, and in July 1943 it achieved the first bombing-induced firestorm against Hamburg, killing about 45,000 people. However German night defenses also adapted. When Harris decided to mount a full-scale assault on Berlin in late 1943, the Luftwaffe shot down so many British aircraft, and bombing results were so disappointing, that the utility of the whole night area campaign was brought into question.
Meanwhile, the Americans had also encountered difficulties. At Casablanca in January 1943, Allied leaders had agreed to a Combined Bomber Offensive (CBO) of round-the-clock attacks. It was rather poorly coordinated, but it did allow each air force to pursue its preferred approach. The most significant USAAF strategic attack of that year was General James Doolittle’s July 1943 attack on Rome from North Africa, which heavily damaged the marshaling yards, limited collateral damage with impressive accuracy, and contributed to the fall of Benito Mussolini’s government. Elements of the Eighth Air Force began bombing the continent from England in August 1942, although they did not fly deep penetration raids into central and eastern Germany until a year later. Losses among unescorted B-17 and B-24 “Liberator” bombers were horrendous, especially during attacks against ball-bearing plants at Schweinfurt in August and October 1943. Although the Fifteenth Air Force in Italy joined the daylight campaign in November 1943, the Americans were unable to sustain such attrition. By the end of the year, such deep attacks on Germany were suspended, and it appeared that the Luftwaffe was on the verge of winning the strategic air war in Europe.
Everything changed, however, with the advent of the Allied long-range escort fighter, most notably the P-51 “Mustang.” In mid-February 1944, the U.S. Strategic Air Forces (USSTAF) began their “Big Week” attacks against German aircraft factories. The air battles that ensued decimated the Luftwaffe, and by the time of the D-day landings in June, the Allies achieved air supremacy over France and air superiority over Germany. The escort fighters began by sticking close to their bombers, but they proved most effective when they were released to sweep against enemy aircraft in the air and on the ground. Because of the American adoption of radar-directed bombing methods through overcast skies, the Germans had little respite even in poor weather, and their losses were increased by many accidents. Although the strategic bombers had an initial priority to operations in support of the coming invasion, Allied airpower had built up to the point that USSTAF commander General Carl Spaatz could begin sustained attacks against oil targets in May. By the fall of 1944, Luftwaffe and Wehrmacht operations were severely crippled by fuel shortages, and concentrated attacks against transportation networks further limited German mobility and economic activity.
During this period, Harris resisted diversions against “panacea targets” such as oil and remained committed to “dehousing” German workers. However, British bombers did sometimes assist with attacks on oil and transportation targets, and their larger loads of bombs could cause considerable damage. The RAF greatly improved its ability to navigate and bomb at night or in bad weather, and it usually achieved greater accuracy than the Americans under such conditions. Even in clear weather, precision bombing did not approach the image often portrayed in the press of bombs dropping down smokestacks. Usually, all aircraft in the B-17 and B-24 formations dropped their loads together, with intervals set between bombs so they would fall a few hundred feet apart. The pattern therefore covered a wide area. As USSTAF strength increased and targets became scarcer, planners became more tolerant of civilian casualties, adopting less accurate radar-directed bombardment methods in bad weather and hitting transportation objectives in city centers.
At least in Europe, American air leaders remained committed to attacks aimed primarily at economic and military targets instead of at civilian morale, a policy that sometimes caused friction with their British allies. There were also differences over bombing in occupied countries, where the British were particularly sensitive to political repercussions. The Americans were willing to bomb any Axis factory regardless of the nationality of the workers, whereas the British preferred to strike any German anywhere. The British also favored heavy attacks on the capitals of Axis allies in the Balkans, although the Americans successfully blocked what they saw as an inefficient and ineffective diversion of valuable airpower. Debates about the relative success and morality of RAF and USAAF bombing have continued to the present day.
The differing national approaches also played a role as the war in Europe approached its end, and both air forces sought an aerial death blow to finish the war. The British plan, codenamed THUNDERCLAP, was based on shattering morale by destroying Berlin. That major assault was conducted by the Eighth Air Force on 3 February 1945. Allied concerns about assisting the Soviet advance helped produce the firestorm that devastated Dresden 10 days later. The corresponding American plan, code-named CLARION, aimed to awe the German populace with widespread attacks on targets in every village. It was eventually changed into primarily a transportation assault because of concerns for efficiency, public image, and even morality. The controversy in Great Britain over the Dresden attack was one factor in the suspension of the strategic air war against Germany in April, although it was not as important as the simple fact that Allied bombing forces were running out of suitable targets.