There have been ample opportunities since 1945 to show that material superiority in war is not enough if the will to fight is lacking. In Algeria, Vietnam and Afghanistan the balance of economic and military strength lay overwhelmingly on the side of France, the United States, and the Soviet Union, but the will to win was slowly eroded. Troops became demoralised and brutalised. Even a political solution was abandoned. In all three cases the greater power withdrew. The Second World War was an altogether different conflict, but the will to win was every bit as important - indeed it was more so. The contest was popularly perceived to be about issues of life and death of whole communities rather than for their fighting forces alone. They were issues, wrote one American observer in 1939, 'worth dying for'. If, he continued, 'the will-to-destruction triumphs, our resolution to preserve civilisation must become more implacable...our courage must mount'.Words like 'will' and 'courage' are difficult for historians to use as instruments of cold analysis. They cannot be quantified; they are elusive of definition; they are products of a moral language that is regarded sceptically today, even tainted by its association with fascist rhetoric. German and Japanese leaders believed that the spiritual strength of their soldiers and workers in some indefinable way compensate for their technical inferiority. When asked after the war why Japan lost, one senior naval officer replied that the Japanese 'were short on spirit, the military spirit was weak...' and put this explanation ahead of any material cause. Within Germany, belief that spiritual strength or willpower was worth more than generous supplies of weapons was not confined to Hitler by any means, though it was certainly a central element in the way he looked at the world.The irony was that Hitler's ambition to impose his will on others did perhaps more than anything to ensure that his enemies' will to win burned brighter still. The Allies were united by nothing so much as a fundamental desire to smash Hitlerism and Japanese militarism and to use any weapon to achieve it. The primal drive for victory at all costs nourished Allied fighting power and assuaged the thirst for vengeance. They fought not only because the sum of their resources added up to victory, but because they wanted to win and were certain that their cause was just.The Allies won the Second World War because they turned their economic strength into effective fighting power, and turned the moral energies of their people into an effective will to win. The mobilisation of national resources in this broad sense never worked perfectly, but worked well enough to prevail. Materially rich, but divided, demoralised, and poorly led, the Allied coalition would have lost the war, however exaggerated Axis ambitions, however flawed their moral outlook. The war made exceptional demands on the Allied peoples. Half a century later the level of cruelty, destruction and sacrifice that it engendered is hard to comprehend, let alone recapture. Fifty years of security and prosperity have opened up a gulf between our own age and the age of crisis and violence that propelled the world into war. Though from today's perspective Allied victory might seem somehow inevitable, the conflict was poised on a knife-edge in the middle years of the war. This period must surely rank as the most significant turning point in the history of the modern age.
— Richard Overy, Why the Allies Won