In the years before World War I, theorists and engineers of military aviation began contemplating a division of responsibility between military aircraft. Large bomber aircraft, with long ranges and heavy payloads, could undertake strikes at distance. Smaller, more maneuverable aircraft could undertake tactical tasks such as reconnaissance, light attack, and winning air superiority.

By the end of the war, several countries had succeeded in manufacturing dedicated bombers and fighters, the former geared towards heavy strike against enemy cities, and the latter (in some part) to the defense of those cities. Over the next seventy years, the actual and perceived balance of capability between bombers and fighters would have an enormous impact in how nations built their military institutions and provided for their defense. This balance would depend to great extent on how effectively fighters could detect, intercept and destroy incoming bombers. Even today, the biggest air forces weight trade-offs between fighter and bomber aircraft, based to some extent on how effectively each type can carry out its missions.

World War I

The strategic bombing campaigns of World War I both began with huge advantages for the bombers. The British lacked much in the way of an early warning system, meaning that German dirigibles could attack with surprise, and interceptors of the time could not climb to the altitudes necessary to defeat the bombers. A typical zeppelin could make around 60mph and carry around 3000lbs of bombs, allowing it to deadly, although on balance minor, damage on British urban areas. These early raids nevertheless inspired terror in civilian populations across England.

Anti-aircraft guns had some success, but early fighter intercepts were unimpressive. In February 1916, the British lost six of twenty-two interceptors to bad weather in a single raid, and failed to shoot down any dirigibles. Additional raids on England were successful, but in September 1916 a British B.E.2c piloted by William Leefe Robinson managed to intercept and down a large dirigible. The B.E.2c was only slightly faster than the zeppelin, but by this point the British had developed a combination of incendiary and explosive ammunition that could turn a dirigible into a death trap. The Germans still had an altitude advantage, but needed to operate at dangerous heights in order to deliver bombs with any accuracy. More importantly, the British had developed an early warning system and airspace monitoring that allowed fighters to respond quickly to dirigible incursions, a critical requirement given how long it took the fighters to reach high altitude. Coast watchers, telephones, and powerful searchlights illuminated the dirigibles as they approached, and gave fighter the chance to get into intercept position. British aviators shot down several more dirigibles across the rest of 1916, making the campaign untenable.

Partially in consequence of the vulnerability of dirigibles, the Gotha Raids began in May of 1917. A gigantic biplane bomber, the Gotha could make 83mph and carry 1100lbs of bombs, and could climb at faster rate than the zeppelins. Early raids, conducted in daylight, had a (for the time) devastating effect on targets in England. A Gotha was lost to an interceptor in July, and from that point the game was on; German success depended on how quickly intelligence of the arrival of the German planes on the coast was relayed to airfields across England. The capabilities of defensive systems increased faster than bombers, however, and the German attrition rate continued to climb for the rest of the war. The introduction of the Sopwith Camel, which could fly at over 110mph and climb at a much faster rate than the B.E.2c, helped shift the equation decisively in the direction of the fighters.

The German strategic campaign against England was not the only such campaign of World War I, but it was by far the most effective. German bombing failed to turn the tide, but the bombers had enough of an effect for aviators around the world to conclude that they might have a decisive effect on future war. Notwithstanding the success of interceptors, aviators in the United States and the United Kingdom focused on the bomber, in part because it offered an argument for the decisive impact of aviation on war.

Inter-war

Debate over the relative effectiveness of fighters and bombers dominated interwar airpower theory. Planners worried that the raids against England were only a taste of the future, and that better-resourced strategic bombing campaigns might destroy industry, cause panic, or even drive a revolution. For their part, aviators tended to play up these fears, as they justified the investment of resources in aircraft development, as well as institutional autonomy. Although different in important ways, the American Billy Mitchell, the British Hugh Trenchard and the Italian Giulio Douhet each emphasized the importance of the bomber. As British parliamentarian Stanley Baldwin declared in 1932, “the bomber will always get through.”

In the United States, a body of theory emerged from Air Corps Tactical School (ACTS) that focused on the ability of self-defending formations of fast strategic bombers to defeat enemy air defenses and destroy enemy industry. Suggestions that pursuit aircraft might be effective against such formations were not welcome. The United States invested heavily in developing bomber technology, culminating in the Martin B-10, which could outperform most of the world’s fighter aircraft when it entered service in 1934. An all-metal two-engined monoplane, the B-10 could reach 210mph and carry 2260lbs of bombs.

British airpower theory developed in different directions, driven in large part by operational requirements in the empire. However, the logic of heavy bombing against enemy population centers remained critical to long-range RAF planning for great power war. But despite the stated importance of strategic bombing, the RAF was not well-supplied with modern heavy bombers when the war began. A trio of medium bombers entered service in the late 1930s, including the Armstrong Whitworth Whitley, the Vickers Wellington and the Handley Page Hampden. Each of these could make more than 200mph and carry in excess of 4000lbs of bombs.

Germany developed several medium bombers for the Luftwaffe, including most notably the Heinkel He 111, Dornier Do17, and Junkers Ju88, all of which could exceed 250mph at altitude and carry more than 2000lbs of bombs. Notably, however, Germany did not expect strategic bombing to win wars independently. Other countries, including Russia, Italy, France and Japan, developed their own medium bomber variants, generally of similar capabilities.

Unfortunately for the bombers, a new generation of fighters was also about to arrive. From the mid-1930s on, all metal monoplane fighters such as the P-36 Hawk, the Bf-109 and the Hawker Hurricane began to enter service. These aircraft could outpace existing bombers while carrying armaments heavy enough to cause serious damage. This did not invalidate the belief that bombers would dominate, but it did mean that fighters would be able to engage on their own terms. The Martin B-10, for example, was hopelessly obsolete by the time the war began.

These air forces also paid some attention to fighter doctrine. Based on the experience of World War I, the Royal Air Force established Fighter Command in 1926, with the mission of defending British interests at home and abroad. Fighter Command offered a greenhouse for innovative thinking about intercepting and destroying bombers. Perhaps most consequentially, in the late 1930s, the British began to experiment with using radio signals to detect enemy bombers as they entered British airspace.

Parting Bombs:

On the eve of World War II, the great air forces of the world were not well-prepared for the clash between fighters and bombers. War forced every country to do the best with what it had, using existing aircraft and force structures as effectively as possible given the circumstances. This would often have tragic results, as the best laid plans crashed into hard reality. But both fighters and bombers would remain relevant for the duration of the war.

Robert Farley, a frequent contributor to TNI, is a Visiting Professor at the United States Army War College. The views expressed are those of the author and do not necessarily reflect the official policy or position of the Department of the Army, Department of Defense, or the U.S. Government.