Many different factors contributed to the production performance of WWII combatants; some of these are shown in figure 5. The most important among them were the underlying economic strength of each country, the relative effectiveness of political and economic leadership, and the impact of enemy military action on aircraft production.

There were big differences in the underlying economic strength of the major aircraft producers. In 1938 the US and the USSR each generated a greater manufacturing output than Germany and Japan combined, with US output being more than twice as high. In the same year Great Britain's output was close to that of Germany and far exceeded Japan's. But while economic strength played a part in determining the level of aircraft production, there were substantial differences in the efficiency with which each country leveraged its economic resources. This efficiency hinged on leadership at both political and operational levels, and overall the Allies performed much better in these areas than the Axis, although there were significant differences from country to country.

Meanwhile, for all of the major combatants except the US, aircraft production was impacted directly or indirectly by enemy action. Factories in Britain, Germany and Japan were subject to enemy air attack, and this problem was only avoided in the USSR by moving entire factories far to the east - a process that was disruptive in itself. Meanwhile, Britain and Japan, and to a lesser extent the USSR, suffered severe disruption of their raw material supply, since virtually all raw materials had to be imported through submarine-infested waters. In Germany, the disruption in material supply came from air attack on the country's transportation system. Again, only the US was largely exempt from the affect of enemy action.

An interesting analysis is to compare aircraft production with pre-war economic strength. By to this measure the most successful major combatant was not the US, or even Great Britain, but Japan. Japan was closely followed by Great Britain with the US following in third place. Relative to their pre-war economic strength, Germany and the USSR were substantially less successful.

The end of World War II lies over fifty-five years in the past, and the US has been the leading military power for more than half a century. From today’s perspective it is difficult to imagine that, prior to World War II the US was in military terms a second rank power. In the 1930s the US had one of the world’s largest navies, but its army was small by European standards, and its armaments industry was correspondingly small. This is reflected in the relatively low level of aircraft production: in 1935 the US manufactured fewer than 500 aircraft. Britain, France, Germany Italy, Japan and the USSR all produced more.

The advent of the war transformed the US into a military superpower, with a corresponding growth in its aircraft industry. From its small pre-war base the US grew to be the world’s largest aircraft manufacturer by far, accounting for close to 40% of the aircraft produced from 1939 to 1945. The US dominance is even greater when the size and complexity of the aircraft is taken into account. By airframe weight the US accounted for 48% of production for the 1939 to 1945 period, and 57% in the peak year, 1944. This dramatic increase was achieved even though the US armed forces did not start to expand significantly until 1940, five years after most European countries.

Several factors combined to enable these remarkable achievements. Before the onset of World War II the US had the largest manufacturing sector in the world, accounting for 32% of world manufacturing output. One contributory factor was simply size, with the US having the largest population of any industrial country apart from the USSR. But even on a per-head basis the US out-produced Great Britain by nearly 20%, Germany by 70%, the USSR by over 200% and Japan by over 600%. The US lead in complex finished goods was even greater; for example, in 1938 the US built around 60% of the world’s motor vehicles. And supporting industries such as steel, aluminum, machine tools and electric power were also well developed.

But airplanes are not automobiles, and an aircraft industry requires specific expertise in designing and building aircraft. In the 1930s, while the US armed forces ordered relatively few aircraft, US manufacturers benefited from the world’s largest commercial airline industry. This airline industry stimulated the development of large aircraft and of powerful and reliable engines. US manufacturers also benefited from purchasing of military aircraft by European powers, especially Britain and France, when they rearmed in the late 1930s. Purchases by European powers doubled US output in the late 30s, bringing many aircraft companies their largest orders. The British and French invested directly in aircraft and engine plants, and even before the Lend-Lease program of 1941 Britain and France had ordered 14,000 aircraft from US factories. European purchasing missions were responsible for ordering into production aircraft such as the P-51 Mustang that would later become the staples of the US air arms.

A third factor that benefited the US industry - at least in relative terms - was that US industry was geographically isolated from both ground fighting and air raids. US manufacturers did not need to move their factories as the Russians did in 1941, nor to disperse their production to avoid presenting large targets for enemy bombers as did the British, the Germans and, later in the war, the Japanese. Most of the required raw materials were readily available domestically or from friendly countries in the western hemisphere.

But while the above factors go some way to explaining the US achievement - and were perhaps necessary to it - they do not account either for the degree to which US industry out-performed all others or the speed with which production was ramped up. Here we have to look to factors of leadership and organization, including the setting of very high goals for production. These goals were partly triggered by overestimates of German production, and partly reflected large numbers pulled out of the air by President Franklin Roosevelt. But the fact that these aggressive targets were largely achieved is a testament to the enormous success of the US economic system in mobilizing resources, people and technology.

Great Britain had always been a major producer of military aircraft, but through the late 1920s and early 1930s military spending had reduced in the face of economic pressures and production had dropped to a low rate. Alarmed at the rearming of Nazi Germany and spurred by the warnings of Winston Churchill and others, Britain started a massive rearmament campaign in the mid 1930s. This rearmament saw the building and conversion of many new aircraft factories, and also the introduction of a new generation of modern aircraft such as the Hurricane and Spitfire.

British production doubled from 1,440 aircraft in 1935 to 2,830 in 1938, and then increased another five-fold to over 15,000 in 1940 - the result of the re-armament measures put in place from 1935 on. From this point the actual number of aircraft grew more slowly with the total for both 1943 and 1944 being just over 26,000, but this relatively slow growth in unit numbers disguised a much more rapid growth in airframe weight as a growing share of production took the form of heavy four-engined bombers. While in numbers of aircraft Britain ranked third after the US and the USSR ­ and also fell behind Germany in 1944 - when measured in terms of airframe weight British production took second place after the US for every year from 1942 on, and also for the 1938-45 period as a whole.

On a per-head basis, British production was very close to that of the US, and outstripped by far that of all of the other combatants. In part the high production per head can be attributed to the advanced state of the British economy; on a per-head basis British pre-war manufacturing output was second only to the US. The much lower total production reflected the fact that Great Britain was a much smaller country with a population of less than a third that of the US.

British production also benefited from the relatively early start made to rearmament, and from the high priority put on aircraft production as opposed to other forms of armament. The aircraft industry was directed by the powerful and effective Ministry of Aircraft Production, and for much of the war got priority for labor and materials. This high priority derived in part from the extension to the air force the traditional role of the Royal Navy in protecting the island nation from overseas invaders. It was also aided by a large overestimate of the production levels achieved by Nazi Germany - in part derived from early Nazi propaganda that exaggerated their output.

British production was achieved in the face of a number of constraints and challenges that were not faced by the US. After war broke out in 1939 the growth of Britain’s aircraft industry faced considerable logistics challenges. Skilled labor was in short supply through the war, and the aircraft industry met its goals only by employing large numbers of women ­ an approach also followed by the US. Britain also faced a major challenge in supply of raw materials, with a heavy dependence on materials from overseas sources, all of which had to be shipped across waters patrolled by U-boats. These challenges in the areas of labor and raw materials were compounded by Britain’s need to disperse its factories to reduce its vulnerability to German air attacks ­ all other things being equal, one large factory is much more efficient than several smaller ones.

At the start of the 1930s the Soviet Union was the world’s largest aircraft producer by far. And as war clouds gathered during the late 1930s, the country’s production grew rapidly: Soviet production quadrupled from 2,529 in 1935 to 10,382 in 1939. Growth dipped in 1940 as the industry switched over to new types and as many factories relocated to the east, and then quadrupled again between 1941 and 1944 to exceed 40,000 units, making the Soviet Union the second-largest producer after the US in terms of number of aircraft. This continued growth after 1941 was achieved despite the fact that in 1941 the German army overran large areas of Soviet territory including many important industrial areas.

Although when viewed in isolation the country’s production appears impressive, when viewed in relative terms it is less so. The country’s share of World aircraft production fell from a quarter in 1935 to a sixth in 1944. In 1936 and 1937 Soviet production was overtaken briefly by that of the rearming Nazi Germany, while from 1940 the lead passed first to Great Britain and then the United States. While the USSR ended the war in second place in terms of numbers of aircraft, when measured by the more significant measure of airframe weight, Soviet production fell to fourth place behind the US, Great Britain and Germany.

The large production in the 1930s is easily explained. The USSR had the largest population of any industrialized countrywith the largest labor force by a considerable margin. Despite 20 years of communist rule, the Soviet Union was the world’s second largest industrial economy after the US, accounting for 18.5% of the World’s manufacturing output in 1938. And unlike the US the USSR maintained a large military establishment throughout this period.

Although the Soviet economic system was very different from those of the US and Great Britain, the country was more successful in expanding aircraft production than any of the Axis countries. Like the Western powers the Soviet Union put aircraft production in the hand of civilian experts rather than the military. The Soviets mobilized many millions of women to work in their armaments industry, and production was motivated by an intense patriotic desire to expel the German invaders from Soviet soil - a major factor in persuading Soviet workers to put up with conditions that would have been totally unacceptable in the West.

Soviet production did have some significant obstacles to overcome. In 1941 the German army overran many factory locations in the western USSR, and factories had to be moved far to the east to put them out-of-range. This move was a major undertaking, although started before the Soviet Union entered the war. Once completed, however, the move put the Soviet factories well beyond the range of German interference, allowing large factories to be built and operated without being subjected to bombing.

From a resource standpoint the USSR was reasonably placed. The country was self-sufficient in most raw materials, although it was dependent on imports for aluminum, one of the key requirements of aircraft production. After 1941 the US became the country’s major supplier of this vital commodity, and no major shortage was experienced, although the only available supply routes were the long, slow and expensive Middle Eastern route through Iran, or the faster but more dangerous route across the North Atlantic.

After being debarred from producing military aircraft following the first world war, Germany started to rearm in secret in the early 1930s, coming into the open with the election of Adolf Hitler as chancellor in 1933. By 1935 Germany produced more aircraft than any other country, although the 3,183 aircraft produced were predominantly training aircraft rather than combat types. By 1939 production had not only more than doubled to 7,350 aircraft, it had been converted largely to combat aircraft. Then in the next four years production increased by another factor of five to over 40,000.

As in the case of the Russian industry, German production seems impressive when viewed in isolation, but the German aircraft industry was also less successful in expanding production than the western Allies. While in 1939 German production was over 25% higher than British production, by 1941 Britain caught up and remained ahead for the remainder of the war. Meanwhile, US production, which is 1939 was half that of Germany, also caught up in 1939 and grew at a much higher rate thereafter. Germany's failure to match the high production volumes of its adversaries severely constrained its capacity to wage war and was a major factor in the eventual Allied victory.

Germany’s relatively poor performance is highlighted by the fact that, relative to the size of its pre-war economy, the country produced just over half as many aircraft as the British and Americans. And this despite a substantial increase in the economic resources and raw materials available following the conquest of many of the surrounding countries between 1938 and 1941.

Germany certainly benefited from a large economy, and from a manufacturing sector that was among the world’s most productive. However, unlike US and British industry, which was oriented towards finished goods, German industry was heavily concentrated in primary industries such as metals and chemicals. The country's automobile industry did not lag far behind the most advanced in Europe at the time, those of France and the UK, but was way behind that of the US. Germany was also tightly constrained by the availability of raw materials, at least prior to its European conquests in 1940.

Above all, the poor German production record relative to the size of its economy and the availability of raw materials is a result of poor management. The biggest culprit was Hermann Goering who, as head of the Luftwaffe, consistently overestimated his own strength and underestimated that of his adversaries, feeding over-optimistic reports to Hitler. Goering also put the grossly under-qualified Ernst Udet in the key position of Chief of the Luftwaffe Technical Office.

Hitler himself contributed to the problem in several ways. Following German successes in 1940 he scaled back all armament production, partly in an effort to maintain support from the populace by maintaining a flow of civilian goods. He accepted Goering’s over-optimistic assessments because they lined up with his own prejudices, and then punished the Luftwaffe when it failed to deliver its promised victory over the RAF in the battle of Britain by channeling resources to other purposes ­ while maintaining the ineffective Goering in his position.

Other management problems included the failure to convert the automobile industry to aircraft production, the failure to mobilize women, and the dominant role played by the military in overseeing production. Luftwaffe directives ensured a continuous series of detailed enhancements that slowed production. In contrast, the civilian-dominated production managers in the Allied countries often forewent enhancements to achieve higher production rates.

As Germany’s fortunes on the battlefield declined after the end of 1942, the country’s aircraft industry saw new leadership, resulting in renewed growth that began to close the production gap, at least with Great Britain. Udet committed suicide and was relaced by the far more effective Erhard Milch, and industrialist Albert Speer played a growing role. This team achieved a dramatic increase in production by 1944, rapidly closing the gap with British production.

This new organization would have been even more successful if it wasn’t for the growing weight of Allied bombing. While many post-war analysts interpreted the growth in German production well into 1944 as proof of the ineffectiveness of the Allied bombing campaign in its primary mission of slowing German production, the effect was certainly considerable. After the war Speer told his interviewers that production could have been 30% higher were it not from the constant barrage of Allied bombing.

Bombing hampered the German production effort is several different ways. Even the threat of bombing forced the dispersal of facilities, forcing the Germans to produce in smaller, less efficient units. They also directed resources to building massive underground factories. Direct damage to production facilities also had a significant impact. An oft-repeated error in analysis has been to conclude that, because facilities were often repaired and up and running only a few weeks after bomb damage, the percentage impact on production was small. But this analysis doesn’t take account the diversion of resources and management attention such interruption imposes on an enterprise. A factory striving to restore production in the face of bomb damage is not focusing its efforts on increasing production. If the same effort made to repair damage was devoted to increasing production, then output would certainly have been higher. Factories also suffered from growing worker absenteeism following bomb attacks on residential areas. And resources that could have been employed building aircraft were diverted to militarily insignificant retaliation weapons such as the V-2 rocket.

Of the five major combatants, Japanese aircraft production was the lowest by far. From 1939 to 1945 Japan produced between one half and two thirds of the number produced by Germany, Britain and the USSR. More significantly, Japanese production amounted to only a quarter of that of its most direct adversary, the US. Moreover, the aircraft built by Japan were on average smaller and lighter than those of the other major combatants, so while the country produced 9% of all aircraft, these amounted to just 6% of worldwide production by airframe weight.

But while in absolute terms Japanese production fell well short of the other major combatants, it can nevertheless be seen as a remarkable achievement relative to the country’s level of development. In contrast to the other major combatants that had highly-developed industrial economies, in the 1930s Japan was still in the relatively early stages of industrialization. Although in population terms Japan exceeded both Britain and Germany in size, the country’s manufacturing output per head in 1938 was a third that of Germany and a fifth that of the US. And the Japan that Europeans and Americans were to fear as a trading competitor lay well in the future: in 1938 this great car producer of the future built fewer than 1% of the world’s motor vehicles, compared to around 10% each for Britain and Germany, and over 50% for the US.

This small industrial base was not the only challenge that Japan had to overcome. Prior to the 1930s the country had no history of designing and producing its own aircraft, and developed this expertise by a concerted policy of buying, testing, copying and improving foreign designs. By the beginning of the Pacific war in 1941 Japanese aircraft were in some respects among the best in the world, and in the initial stages of the war Allied pilots were amazed at the range, speed and maneuverability of the Zero fighter. But Japan always lagged in the performance of its engines, and this was a handicap that forced Japanese designers to compromise on armament and protection, which had a big impact on their success in combat.

Both before and during the war, Japanese industry was critically short of many raw materials ­ which had been a major factor persuading them to go to war in the first place. Almost none of the raw materials required by the aircraft industry were to be found in the Japanese home islands, and they had to be imported from territories such as Indonesia that Japan conquered in 1942. The problem was that the sea lanes through which these raw materials had to be transported were the hunting grounds of US submarines, and later on of US aircraft, and supply could never be assured. Shortage of alloys such as nickel for high quality steels led to a reduction in steel quality and thus to reliability problems that greatly reduced the effectiveness of those aircraft that were produced.

Another major problem impacting Japanese output was in the organization of production. The country was run by the armed forces. While the major industrial concerns supported the war effort, civilians did not drive production decisions as they did in both the west and the Soviet Union. There was a proliferation of different models of aircraft, resulting in the shortest production runs of any major power, and this proliferation extended to subsystems such as weapons, which Japan produced in greater variety than any other combatant. This proliferation was exacerbated by the most important conflict waged by the Japanese army and navy ­ that with each other. Not only did this lead to wasteful duplication, but the army and navy also fought over resources, even using different ships to transport raw materials from overseas.

Until late 1944 the Japanese aircraft industry was not troubled by direct attack. But when US bombing started in earnest in early 1945 aircraft production was badly and directly hit. Japanese towns proved highly combustible, and much production was distributed among small workshops in residential areas which burned to the ground in the immense fires started by US attacks. By the time of the Japanese surrender in August 1945, Japanese production had been reduced to a small fraction of its peak a year earlier.