strategic bombing during World War II

print Print
Please select which sections you would like to print:
verifiedCite
While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.
Select Citation Style
Feedback
Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login).
Thank you for your feedback

Our editors will review what you’ve submitted and determine whether to revise the article.

External Websites

strategic bombing during World War II, the mass bombing of military targets and population centres during World War II. Large multi-engine bombers operated in formations (sometimes numbering 1,000 or more aircraft) that were intended not to evade enemy defenses but to beat them back or simply overwhelm them.

This examination of the Allied strategic bombing campaign was written by one of its chief architects, Gen. Carl Spaatz, U.S. combat air commander (from January 1944) in World War II and the first chief of staff (1947–48) of the independent U.S. Air Force. It originally appeared in Britannica’s four-volume set 10 Eventful Years: A Record of Events of the Years Preceding, Including and Following World War II, 1937 Through 1946, published in 1947. It has been edited for style and clarity, but the author’s unwavering belief in the supremacy of air power remains undiminished throughout the article.

Origins of strategic bombing

The theory and practice of strategic bombing began in World War I but did not advance beyond the rudimentary stage. The airplane had not yet developed a sufficient load capacity to serve as a decisive offensive weapon. It was used mostly for reconnaissance and for tactical support of armies, with only experimental air effort applied to strategic objectives.

The weapons then available for surface war favoured defense over offense. As a result, the Western Front remained comparatively stationary for the greater part of four years, yielding a blood bath of positional war. Superiority of defense was a concomitant of the relative immobility of firepower entrenched behind barbed wire. Land offensives were restricted by the lack of a mobile armoured weapon. This deficiency was characteristic of surface war of the period in which the opponents were relatively equal and similar in personnel, distribution, weapons, and mobility. The objectives, of necessity, were limited to the defeat of the immediate military forces in the field and the progressive seizure of space. The tank, a mobile and offensive weapon, was not effectively employed until the final phase of the war. “The black day of the German Army,” according to German military chief Erich Ludendorff, was August 8, 1918, when the Allies launched their coordinated tank offensive at the Battle of Amiens. This battle marked the beginning of what came to be known as the “hundred days,” a string of Allied successes on the Western Front that led to the collapse of the German army and the end of the war. Short of a breakthrough such as this, the only other means to force the enemy’s collapse in two-dimensional war was the external blockade, which deprived an enemy army of outside sustenance.

The consequence of the superiority of defense resulting from immobility of firepower was that World War I, despite the many attacks and counterattacks, remained a stalemate until the closing months, when U.S. reinforcements upset the balance between the opposing forces. The inescapable high cost of successful land offensives predetermined the outcome of a war of attrition; the side with the greatest resources in personnel and matériel, including food, would emerge victorious. Germany was conquered, but not invaded, during the period of combat. Under pressure of external blockade, Germany’s “home front” collapsed, leaving its armies without support and therefore with no recourse but surrender. The “home front” was the Achilles heel.

The conclusion seemed plausible that constant increase of firepower, mounted in defensive works, would insure the continued superiority of defense over offense, given equality of forces engaged, and provided the “home fronts” remained unbroken. In the following years some authorities enunciated this dictum as an incontestable military doctrine. Its physical expression was the Maginot Line, the classical pattern for a stalemate war.

The offensive character of the tank was a challenge to the idea of impregnable defense in that it increased the mobility of firepower but within the limits imposed by its two-dimensional movement in surface warfare. Some new capacity was necessary. Proponents of air warfare believed that the airplane, operating in three dimensions, could not only give greater mobility to the offense but also could break the deadlock of positional war by its capacity to maintain an internal blockade on the enemy’s “home front.”

Get Unlimited Access
Try Britannica Premium for free and discover more.

The clue to this undeveloped capacity lay in the relatively insignificant experience with strategic bombing in World War I. Bombing operations were carried out with slight success by both sides in 1916. The German attacks on London in the summer of 1917, however, pointed to the strategic offensive potentials of air weapons. These attacks led to the creation of the Royal Air Force as a separate service and to the establishment (within the RAF) of a special bombing force for direct action against the heart of the German industrial system. In August 1917 Gen. Jan C. Smuts, in recommending air operations independent of the army and navy to the war cabinet, declared, “aerial operations…may become the principal operations of war, to which the older forms of military and naval operations may become secondary and subordinate.” The RAF dropped 543 tons of bombs on Germany in 1918, causing 2,589 casualties and damage amounting to $6,000,000. These operations by light airplanes were small compared with those of World War II, but they did demonstrate the efficacy of the strategic air offensive.

Prophets of the offensive use of air power included Marshal of the Royal Air Force Lord H.M. Trenchard; Winston Churchill, British minister of munitions, 1917; Brig. Gen. William Mitchell, U.S. Army Air Corps; and Gen. Giulio Douhet, Italian air force, author of Il dominio dell’aria (1921; The Command of the Air, 1942). The RAF staff college and the U.S. Army Air Corps tactical school focused attention on the necessity for a new means of offense to reach the vital centres of an enemy’s war production. From these studies there was gradually evolved a new concept based on the capacities of the airplane. The airplane was not limited by geography, except for its requirement of surface bases. Its one serious limitation—weather—could be mastered by human ingenuity in making and using electronic instruments. The airplane came from anywhere; it went everywhere.

The basic problem in designing a decisive service weapon is the necessary compromise between the contradictory imperatives of firepower, mobility, and protection (armour). In general experience, one of these is achieved in a weapon only at the sacrifice, to some degree, of the others. The airplane is peculiar in that it not only harmonizes the three imperatives but combines them to a high degree. Its firepower is measured by the allotment in its load capacity to armament and bombs, allowance being made for fuel and crews. It has unprecedented mobility in three dimensions. Speed and altitude are its principal armour. Its offensive character is determined by the extent of its radius of action and by power of penetration equal to its reach. These qualities made the airplane a decisive weapon of a high order.

The mobility of the airplane vastly extended the reach of firepower and created a new large-scale capacity for offense. It brought the enemy’s “home front” within immediate range during hostilities, thus altering the meaning of time and space in war operations. This capacity was the basis for changing the concept of war from limited conflict between armed forces in the field (nations in arms) to all-inclusive combat between the total human and material resources of the opposing nation-structures. The ultimate national aim of all military action is to break the enemy’s power and will to resist. Before proceeding to this ultimate objective, land forces are obliged to attain a limited intermediate objective—the defeat of the corresponding type of hostile force.

Air power, on the other hand, acts not only against the corresponding hostile air force but against all the hostile forces, land, sea and air. In addition, by reason of its power for offensive penetration, it proceeds to direct assault on the ultimate unlimited objective of all forces—the enemy’s national will, the “home front.”

The concept of strategic air offensive

The nine fundamental principles of war as outlined by the U.S. War Department in its Training Regulation 10–5, 1921—objective, offensive, mass, economy of force, maneuver, unity of command, security, surprise, and simplicity—were evolved during centuries of land warfare and were considered immutable. But air power was without the guidance of precedents for application of its peculiar capacities. The concept of the strategic air offensive could be stated in terms of the nine immutable principles, regrouped under the three headings: objective, means, and application.

Objective

In executing the national war aim of breaking the enemy’s will to resist, air power may be employed to attack the hostile air, land, and sea forces or to attack the enemy’s national infrastructure, depending on the enemy’s most vulnerable sources of strength. Against a heavily industrialized enemy, its maximum contribution to the national war aim is through strategic effort. It thus has both a mission which is sometimes coordinate, and sometimes subordinate, to the land and sea forces and an independent mission of its own.

Its tactical mission is the destruction of military forces. Maintenance of air cover over the land forces by bombers and fighters includes preparation for surface advance by assault on enemy ships, troops, and supply lines; local control of the air; isolation of the battlefield; and airborne operations.

The independent strategic mission is destruction of warmaking capacity. The main targets of an air offensive are not the enemy’s military forces in the field but the arsenals, essential war industries, transport systems, communications, fuel supplies, and other elements that sustain the national will on the “home front,” including civilian morale. A primary purpose is to destroy the enemy’s capacity to create war power and to maintain the battle. These vital objectives had formerly been accessible on a decisive scale only at the end of successful surface campaigns. They could be reached by air power regardless of the tide of surface battle, or even when surface forces were not engaged.

Systematic destruction of the enemy’s sources of war power on the “home front” breaks the will to resist through paralysis of means. To the indirect, external blockade is added a direct, internal blockade which disrupts the means of sustenance inside the area occupied by the enemy’s military forces and population. In a condition of progressive strangulation of the war effort, the enemy loses capacity to maintain the battle and is forced to collapse from within. This assault on the whole national structure is the peculiar capacity of air power and its dominant mission in war.

Means

The means for fulfillment of the strategic concept of air power are organized air forces, adequately equipped with airplanes of various types with the speed, range, and firepower necessary to execute their particular missions. Auxiliary instruments include bomb sights, navigational aids, radio, aerial cameras, etc. The national sources of supply must be adequate to build and maintain the air forces and to replace battle wastage of personnel and matériel.

Application

The application of air power includes those principles of war not listed under the objective. A special requirement is advance knowledge of the targets most vital to the enemy’s war effort. These are selected from available intelligence sources and confirmed by aerial photography.

The principle of the offensive is inherent in the airplane; it cannot remain still. The methods of the offensive are attrition, destruction, external and internal blockade, and capture. Security, in combat and at the airbase, is achieved by control of the air. This is gained by progressive destruction of the enemy’s air force in the air and on the ground and by attacking the enemy’s industrial base to destroy its replacement capacity. The offensive for control of the air in its early stages parallels the strategic mission, as an air force on the defensive can be forced into the skies to engage in combat by bombing “sensitive” targets. Control of the air is essential to freedom of action of all forces, land, sea, and air. When the enemy’s air force has been neutralized to the point where it can not effectively intercept strategic missions, the degree of air control advances to air supremacy which, if maintained, is tantamount to victory.

Air power achieves the principle of mass more effectively than any other armed power. By its extreme mobility, it attains an unprecedented concentration of force over single targets from bases separated by hundreds, and eventually thousands, of miles.

Economy of force is the efficiency which results from accurate bombing of the primary objective with the least expenditure of manpower and equipment and by avoidance of dissipation of strength on secondary operations. Air power is not committed to position in battle; its units retire to base to prepare for renewal of the assault. The rapid turnaround schedules permit a high degree of sustained effort on targets marked for destruction.

Movement is characterized by high flexibility in the tactical maneuvers of combat and in employment. Strategic air forces may be used tactically; tactical air forces may be used strategically. Any component, within the limits of its capabilities, may be shifted from one target to another, from one type of operation to another, or from one theatre of war to another in shuttle operations. High flexibility is a dominant characteristic of air power.

Surprise is elemental in air warfare. The enemy can never be certain of the target selected for attack. Feint attacks, camouflaged efforts, and changes in direction are possible while missions are in flight. Diversionary missions cannot be evaluated in time to take successful countermeasures.

Simplicity, through unity of command, is a prerequisite of the air offensive to insure integration of effort under the principle of mass. Cooperation is attained between strategical and tactical air forces, between bombers and fighters, and between the air and surface forces by careful observance of timing. Coordination among the air, land, and sea forces is achieved through a supreme commander and the overall offensive plan.

The combination of new medium, new capacity for offense, and new concept of total war enabled commanders to raise their sights over the traditional line-of-war to the enemy’s war capacity in the rear. By its ability to utilize increased firepower to enlarge rather than reduce the mobility of armed forces, air power abolished the stalemate of positional war. By its independent strategic mission to force collapse of the national structure, it could shorten the term of hostilities. As the new and supreme instrument of national will, air power altered the dynamics by which nations at war survive.

Strategic employment of air power

The concept of strategic air offensive was not given an adequate tryout until the final year and a half of World War II. Air operations between the two world wars (carried out by the Japanese against China, the Italians against Ethiopia, and the German Condor Legion against the Republicans during Spanish Civil War) were necessarily tactical because of the lack of strategic targets in such areas. One notable exception was the German terror bombing of the Spanish city of Guernica (April 26, 1937). Hundreds of civilians were killed in an attack that destroyed large portions of the historic Basque city.

German air campaigns

The Germans, in preparing for World War II, designed a large air force for tactical support of fast-moving ground troops, without an independent strategic mission of its own. They had not developed the strategic bombing concept. Their light and medium bombers (Junkers Ju-88, Heinkel He-111, and Dornier Do-17) were inadequately armed, and the only long-range heavy bomber deployed by the Luftwaffe, the Heinkel He-177, saw extremely limited use. The Germans used their fighters defensively in close support of the bombers instead of offensively in general support.

Because of a faulty offensive concept, the Luftwaffe failed to concentrate primarily on the RAF and subsequently on industry and ports. They were unable to establish control of the air against the superb eight-gunned British fighters (Spitfire and Hurricane), which were aided by the warnings of the secret Chain Home radar system. Consequently, despite the Germans’ numerical superiority, their air offensive in the Battle of Britain (1940) and the German bombing campaign during the Blitz (1940–41) were doomed to failure.

British air campaigns

The Royal Air Force did have a strategic bombing concept, but its available aircraft were inadequate for the mission. Daylight raids on German targets in 1940 resulted in prohibitive losses. The RAF Bomber Command was forced into night bombing from 1940 onwards. It was not until 1942 that the development of radio navigational aids and the improvement of four-engined bombers (particularly the Lancaster) made the night operations of Bomber Command demonstrably effective in destroying German war capacity. The British heavy night bomber, which sacrificed defensive armament to bomb load, was successful to a limited degree while operating unsupported in its strategic tasks by U.S. heavy day bombers; it remained the greatest load carrier of the war in Europe.

With its new equipment and more effective technique for concentration, Bomber Command, under Air Chief Marshal Sir Arthur T. Harris, was able to begin mass attacks on the concentrated German industries (the first mission was over Cologne on May 20, 1942, when 1,043 bombers dropped 2,000 tons in 90 minutes). Subsequently, RAF area bombing became the night shift in the round-the-clock strategic Allied air offensive; in smashing Germany’s national infrastructure, it had the effectiveness of a titanic sledgehammer. Later, because of improved techniques in aiming, night bombing from medium altitude by the RAF achieved degrees of accuracy and economy of force unsurpassed by other forms of air attack on specific and individual targets.

U.S. air campaigns in Europe and the Pacific

Shortly after World War I, U.S. air leaders began to formulate ideas for the correct methods of using air power as the new decisive instrument in war. These ideas gradually assumed the status of air doctrine—the basis of the U.S. version of the strategic bombing concept.

The strategic plans of the U.S. Army Air Forces (USAAF) envisaged precision bombing from high altitudes in daylight, aided by the secret Norden bombsight. The prohibitive losses incurred by the German and British daylight missions were to be prevented by more and heavier guns on the bombers and the use of tactical formations in combat to gain an intense concentration of protective firepower.

At the moment of Pearl Harbor, the USAAF confronted war in Europe and the Pacific without the means of putting its strategic bombing concept into operation. It did have the advantage of time to prepare while the Allies maintained the battle, of an enormous national industrial establishment for forging the weapon, and of a vast reservoir of U.S. youth capable of being trained in air techniques.

During the ensuing two years the USAAF under the command of Gen. Henry (“Hap”) Arnold built the striking force necessary to execute the concept. Its strength, which was 43,118 personnel and 2,546 airplanes in 1940, was expanded to 2.3 million total personnel and 80,000 airplanes in early 1944. Technical training was necessary in the organization of air and ground crews, as well as in intelligence and target analysis, radio, tactical air doctrine, etc. Mastery of the new technique kept pace of the weapons—B-17 and B-24 heavy bombers and P-38, P-47, and P-51 fighters for escort. The first heavy bombing unit of the 8th Air Force arrived in Great Britain on June 10, 1942. The first mission of the 8th Bomber Command was an attack by 12 B-17s on the Rouen marshaling yards on August 17, 1942. On the following day, U.S. fighters, P-38s, made their first sorties.

Day bombing was tentative and experimental until the Casablanca directive was issued by the combined chiefs of staff on January 21, 1943. It sanctioned the “destruction and dislocation of the German military, industrial, and economic system, and the undermining of the morale of the German people to the point where their capacity for armed resistance is fatally weakened.” To implement this directive there was drawn up “the combined bomber offensive plan” based on an operations analysis report. This plan, also called “Operation Pointblank,” was approved by the combined chiefs of staff on June 10, 1943, and issued to the air commanders of the RAF and the USAAF. The order of target priorities established were: (1) submarine construction yards and bases, (2) the aircraft industry, (3) the ball bearing industry, (4) the oil industry, (5) synthetic rubber plants, and (6) the military transport vehicle industry. This order of priorities changed as the air offensive progressed.

During 1943 the 8th Air Force carried out strategic missions with insufficient force to insure control of the air over the targets. Losses threatened to become prohibitive. The development of long-range escorts, achieved by installing additional fuel tanks in fighters, solved this problem and permitted deeper penetrations. By the end of 1943, the 8th Air Force attained the necessary build-up of strength for effective execution of its strategic mission. The advance of the Allied forces across North Africa to Italy led to activation of the 15th Air Force on November 1, 1943, with bases in the Foggia area. This made possible the coordination of bombing attacks from two theatres on the same German targets, implementing the principle of mass.

The coordination of the strategic bombing effort by the 8th Air Force, commanded by Lieut. Gen. James H. Doolittle, and the 15th Air Force, commanded by Maj. Gen. Nathan F. Twining, was the function of the headquarters of the U.S. Strategic Air Forces, established in Great Britain on January 6, 1944, under the command of Lieut. Gen. Carl Spaatz. These air forces were in two theatres of operations, the European under Gen. Dwight D. Eisenhower and the Mediterranean under Gen. Sir Henry Maitland Wilson. The reach and power of the strategic air arm had not made sufficient impact on the thinking of military strategists to cause organization of theatres of war in conformity with the capability of the most elastic, far-reaching, powerful weapon. Under this condition, the difficulties of operating the U.S. strategic air forces in Europe were greatly augmented. However, by frequent conferences between Spaatz and Lieut. Gen. Ira C. Eaker, commanding general of the Allied air forces in the Mediterranean who had administrative control of the 15th Air Force, whole-hearted cooperation and effective coordination of effort was obtained. Coordination within U.S. Strategic Tactical Air Forces was attained by appointment of two deputy commanding generals, Maj. Gen. F. L. Anderson, operations, and Maj. Gen. Hugh J. Knerr, administration (supply).

The absolute necessity for furtherance of the Anglo-U.S. strategic mission and of preparations for surface invasion of the continent was control of the air over Germany. This could be won only by cutting off the replacements of the German air force and by fighting its existing force out of the sky. The rising scale of RAF night bombing of industrial concentrations, augmented by U.S. daylight attacks, led to German countermeasures. In 1942 the Germans began dispersal of aircraft factories to the deep interior. They planned to quadruple their monthly output of single-engined fighters by April 1944. The 8th Air Force began its offensive for control of the air by an attack on the Focke-Wulf plant at Bremen on April 17, 1943. On six successive days in late July, it attacked the German aircraft industry so successfully that the production curve, which had attained double the output of 1942, was turned downward. The climax came in late February 1944 (the “big week"), when during six days of perfect weather the RAF/USAAF team dropped 16,506 tons of bombs in a series of attacks on the German aircraft industry. These fatally reduced its replacement capacity. German aircraft production subsequently recovered, but the Allies retained control of the air during the remainder of the war.

The combined chiefs of staff retained final control of strategic bombing in Europe throughout the period of hostilities after the U.S. entry into the war. Until April 14, 1944, their designated agent in exercise of control was Air Chief Marshal Sir Charles Portal, who as chief of air staff was ipso facto a member of the combined chiefs of staff. From that date until September 15, 1944, the strategic air forces were placed at the disposal of the supreme commander, Eisenhower. During this period they were used to prepare for and support the surface invasion of the continent (Operation Overlord). Coordination between the tactical and strategic air forces was effected by the deputy supreme commander, Air Chief Marshal Sir Arthur Tedder, as representative of Eisenhower. On September 15, 1944, the strategic air forces reverted to the direct control of the combined chiefs of staff. Portal and Arnold were designated joint agents, with Air Marshal Sir Norman Bottomley and Spaatz charged with coordination in the field.

From April 1944 onward the immediate objectives were transportation systems, with increasing effort assigned to synthetic oil production and other strategic targets of a vital nature. Total German production and imports of oil dropped from 918,000 tons per month in the first quarter of 1944 to 319,000 tons in the last quarter, a decline of two-thirds caused preponderantly by the attacks of the strategic air forces. The effect of the oil shortage was catastrophic for all the German armed forces. The German ground troops literally ran out of oil in the Battle of the Bulge (December 16, 1944–January 16, 1945). Destruction of the German oil supply was the climactic fulfillment of the strategic air offensive in Europe. By February 1945 most of the remaining airplanes of the German air force, including the jet-propelled Messerschmitt Me 262, were pinned to the ground by lack of fuel. Consequently, the Allied strategic air forces could attack at will, with negligible loss, any part of Germany’s armed forces or national structure selected for destruction. Total air supremacy was achieved over the whole area of the European war.

On April 16, 1945, orders were issued to the strategic air forces as follows: “The advances of our ground forces have brought to a close the Strategic Air War waged by the United States Strategic Air Forces and the Royal Air Force Bomber Command. It has been won with a decisiveness becoming increasingly evident as our armies overrun Germany. From now onward our Strategic Air Forces must operate with our Tactical Air Forces in close cooperation with our armies.”

Until the arrival in sufficient numbers of very heavy, long-range bombers—B-29s—the air mission in the Pacific was tactical support of the navy and the amphibious forces. The objectives were Japanese land, sea, and air forces, and islands which were utilized as bases as the offensive closed on Japan proper. The strategic mission began in the summer of 1944 with small attacks on the industries of Japan by B-29s based in China. Attacks of similar weight were begun in November 1944 from the newly acquired bases on the Marianas. With the decimation of Japan’s remaining skilled pilots at the battles of the Philippine Sea (June 19–20, 1944) and Leyte Gulf (October 23–26, 1944), the necessary control of the air had already been won. On March 9, 1945, Maj. Gen. Curtis LeMay, commanding general of the 21st Bomber Command (the striking force of the 20th Air Force, then commanded by Arnold from Washington, D.C.) initiated the all-out mass offensive by low-level incendiary attack.

The U.S. Army strategic air forces, under the command of Spaatz, was activated July 11, 1945, with headquarters at Guam. The attacks on Japan continued at accelerated frequency and unbearable intensity. The dropping of the two atomic bombs, one on Hiroshima on August 6 and the second on Nagasaki on August 9, merely served as justification for the capitulation. This came on August 14, 1945, by the government of a nation long since defeated. A surface invasion proved unnecessary. For this reason the air offensive against Japan was the classic prototype of fulfillment of the strategic bombing concept in World War II.

In its strategic effort (1942–45) the USAAF expended 1,050,710 U.S. tons of bombs against Germany and 179,967 tons against Japan. In similar operations the RAF Bomber Command expended 989,320 U.S. tons against Germany (1941–45) and 13,730 tons against Japan (1943–45). Both air forces expended considerable additional tonnage in tactical operations of the air war. The combination of bombing by day and by night round-the-clock fulfilled the Casablanca directive of the combined chiefs of staff.

Assessment of the Allied strategic bombing campaign in World War II

The two following extracts serve as overall assessment of the strategic air war (from the Overall Report [European War] of the United States Strategic Bombing Survey, September 30, 1945):

Allied air power was decisive in the war in Western Europe….In the air, its victory was complete; at sea, its contribution, combined with naval power, brought an end to the enemy’s greatest naval threat—the U-boat; on land, it helped turn the tide overwhelmingly in favor of Allied ground forces. Its power and superiority made possible the success of the invasion. It brought the economy which sustained the enemy’s armed forces to virtual collapse, although the full effects of this collapse had not reached the enemy’s front lines when they were overrun by Allied forces. It brought home to the German people the full impact of modern war with all its horror and suffering. Its imprint on the German nation will be lasting.

From the Summary Report (Pacific War) of the United States Strategic Bombing Survey, July 1, 1946:

The physical destruction resulting from the air attack on Japan approximates that suffered by Germany, even though the tonnage of bombs dropped was far smaller. The attack was more concentrated in time, and the target areas were smaller and more vulnerable. Not only were the Japanese defenses overwhelmed, but Japan’s will and capacity for reconstruction, dispersal, and passive defense were less than Germany’s.

The time lapse between military impotence and political acceptance of the inevitable might have been shorter had the political structure of Japan permitted a more rapid and decisive determination of national policies. Nevertheless, it seems clear that, even without the atomic bombing attacks, air supremacy over Japan could have exerted sufficient pressure to bring about unconditional surrender and obviate the need for invasion.

Based on a detailed investigation of all the facts, and supported by the testimony of the surviving Japanese leaders involved, it is the Survey’s opinion that certainly prior to 31 December 1945, and in all probability prior to 1 November 1945, Japan would have surrendered even if the atomic bomb had not been dropped, even if Russia had not entered the war, and even if no invasion had been planned or contemplated.

World War II was won through coordinated effort of all forces, land, sea and air, organized in overall offensive plans. Air power did not attain its necessary striking potential until the closing 18 months. It was the new instrument of war and became the spark to success of all forces engaged. The national structures of Germany and Japan were disrupted; their defenses saturated; their “home fronts” dissolved in rubble. This appalling penalty was visited upon nations unable to control the air over their own territories.

Except for the two atomic bombs on Hiroshima and Nagasaki, the bombs carried the conventional type of explosives. A very small percentage of the total tonnage expended, if put in the form of atomic bombs, would have achieved the same results. Carrying a nation’s power through the air and applying it to strategic objectives on the enemy’s “home front” had become the most powerful means to wage war.

Development of the heavy bomber was decisive in the first total war of history. Further evolution of the strategic air concept would include development of guided missiles. The military necessity of the strategic air concept thus epitomized the future issue between possible totality of destruction and the survival capacities of technical civilization.

Carl Spaatz The Editors of Encyclopaedia Britannica