WW2: Why did the Allies win the Second World War? (2024)

Western Allied industrial, maritime and air power were fundamental to destroying the German war machine. But to win, it was crucial to take ground and destroy the forces holding it, and on this score, it was the eastern front where the Wehrmacht was broken most emphatically.

For me, it was Hitler and his generals’ underestimation of the Red Army, coupled with their ideology-­suffused faith in their own superiority, that were most decisive to German defeat. Not all commanders succumbed to this mindset during the run­up to the invasion of the Soviet Union, but many did. Their military intelligence substituted hard facts about the Red Army with arrogant, racially coloured assumptions of chaos and incompetence. All of this blinded them to the Red Army’s true strength, and to the perilously uneven state of their own forces.

The Red Army’s initially calamitous response to the invasion looked set to prove the Germans right. But the German advance took increasingly grievous losses to Soviet resistance, and its mobility was progressively eviscerated by the country’s immense distances, harsh environment and often ramshackle transport infrastructure. By the time the Germans reached the gates of Moscow in December 1941, the blitzkrieg was already exhausted, and with it expired their one chance of decisive victory.

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Over the following 18 months, the Wehrmacht strove repeatedly to regain the initiative – most famously at Stalingrad – but failed to do so to any decisive extent. All the while, the Red Army’s own fighting power burgeoned on all counts. It was fuelled by immense if brutally executed feats of Soviet industrial production, and increasingly by vast economic aid from the United States. Following further German failure at Kursk in July 1943, the Red Army pressed forward inexorably, and the Wehrmacht was never again able even to attempt to claw back the advantage.

Ben Shepherd is reader in history at Glasgow Caledonian University and the author of Hitler's Soldiers: The German Army in the Third Reich (Yale, 2016).

By James Holland

Historians tend to view the Second World War predominantly through the prism of strategic decisions and fighting at the coalface, when an arguably more important consideration is how combatant nations marshal their resources. I’ve recently been looking at a photograph of tanks being loaded onto landing ships before the Allied invasion of Sicily in July 1943 (above). It suggests exactly what it is: a demonstration of immense materiel power and wealth. What is so astonishing is that, at the start of the war, neither Britain nor the United States had much of an army and both had comparatively small air forces – very small in the case of the US. Yet in four years, they had grown exponentially and were fighting equally in the air, on land and at sea, on a truly global scale. They were also providing materiel support to the Soviet Union.

That the United States became the arsenal of democracy is reasonably well known, but the speed with which it achieved this is less understood. Nor is it much known that Britain’s military growth was also extremely impressive – to the tune of 132,500 aircraft, for example, and providing 31 per cent of all supplies to the US in the European theatre of operations. Lend­Lease cut both ways.

Food, materiel and fuel shortages for the Axis powers ran across the board

Key to this was prioritisation, which was dictated by a very clear goal or endgame, and brought research, development and production into very sharp focus. In contrast, both Germany and Japan were, after initial gains, caught in a production spiral from which they simply could not recover. Food and fuel were their biggest shortages, but materiel failure ran across the board. Japan didn’t sink the aircraft carriers at Pearl Harbor, and Germany didn’t win the Battle of Britain; while Britain and the US were still fighting, their materiel power – their ‘big war’ strategy – meant victory was assured.

James Holland is a historian and author. He is currently working on a new book about the 1943 Sicily campaign.

Hitler’s June 1941 advance into the USSR – known as Operation Barbarossa – was the decisive moment of the war, because there­ after, at unspeakable human cost, the Red Army did the heavy lifting: first to contain the Germans, and finally to defeat them.

It may be argued that American supplies – everything from aluminium to spam, boots, trucks and telephone cable – made an important contribution to Soviet victory, but in the crucial first 18 months of the eastern war, western materiel reached the USSR in modest quantities, making only a marginal contribution to the Soviet war effort until 1943, by which time the battle of Stalingrad had been fought and won.

As the great historian Sir Michael Howard often said, counter­factuals are foolish, because once one variable changes, infinite possibilities are opened up. But I have always thought that if Hitler, instead of launching Barbarossa, had reinforced Rommel and completed the conquest of the Mediterranean and Middle East, as I believe he could have done, Churchill’s government would not have survived. It might well have been replaced by a Tory administration that sought a compromise peace with Germany. After the experience of the First World War, I don’t think the British people (any more than the French) had the stomach for the ghastly struggle of attrition that proved necessary on the eastern front before the Germans were driven back. It is unlikely there was ever any easy route to winning the Second World War, or has been in any great clash between more or less evenly matched modern industrial powers.

I suppose a scenario can be pondered wherein the western Allies dallied until an atomic bomb was built, then used it against Germany. But that presupposes US entry into the war, and indeed many other things. I rest my case that an enormous amount of killing and dying had to happen before the Nazis were crushed, and though it did not seem so to the western Allies and their peoples at the time, posterity can see that the Soviets did most of it.

Sir Max Hastings is an author and journalist, whose books include Chastise: The Dambusters Story 1943 (William Collins, 2019).

Watch: Are we in denial about our role in WW2? Keith Lowe explains – in 60 seconds

By Andrew Roberts

Between 1941 and 1945, the Soviet Union produced 58,681 T-34 tanks. They were not the most powerful tanks in terms of firepower, nor the fastest, but their vast numbers won battle after battle for the Red Army, which is what ultimately destroyed Nazi Germany. “In the end,” Stalin is reputed to have said of the T-34, “quantity becomes quality.” Although the German Panzers were superior individually to the T-34, they could not overcome the odds of three or four or sometimes five to one that the Soviets were capable of deploying in key battles such as Kursk in July–August 1943.

A central statistic for the Second World War is that, for every five Germans killed in combat – not, therefore, including civilians killed in cities in the Allies’ Combined Bomber Offensive – four died on the eastern front. While we in the west understandably concentrate on events like D-Day, Arnhem and the battle of the Bulge, much larger campaigns were being fought in the east, allowing the Red Army to advance on Berlin, forcing Hitler to kill himself. For example, in Operation Bagration in Byelorussia from June to August 1944, some 450,000 casualties were inflicted on Ger many’s Army Group Centre. That is why the T-34 (which includes two main variants, the T-34/76 and T-34/85) was the most decisive factor in destroying nazism.

Andrew Roberts is a military historian whose most recent book is Leadership in War (Allen Lane, 2019).

By Nick Hewitt

Fundamentally, Allied sea power ensured Nazi Germany’s defeat. During the dark days of 1940 and 1941, Allied warships and other craft saved a succession of armies from certain destruction, evacuating them first from Norway, then famously from France via Dunkirk, and finally from Greece and Crete, despite relentless enemy attempts to prevent them. After France fell, it was the Royal Navy that saved Great Britain from invasion.

Warships protected convoys of merchant ships, carrying vital supplies from the United States, Canada and worldwide, in the face of determined Axis attempts to interdict them. This kept first Britain and then the Soviet Union in the fight. After the US entered the war in December 1941, sea power guaranteed the build-up of the overwhelming American military and air power required to take the fight back onto the continent.

Sea power kept British Commonwealth armies fighting in north Africa, despite devastating enemy attacks in the Mediterranean and perilously long supply routes around the Cape of Good Hope. Later, it gave the Allies the flexibility to move armies around the world, seizing the initiative and hitting their enemies where they were most vulnerable, from Madagascar, Morocco and Algeria to Sicily and southern Italy. For the western Allies, the Second World War was largely a naval war, fought with expeditionary armies.

Finally, it was overwhelming Allied sea power – a staggering 7,000 ships and vessels of all sizes – that put a vast Allied army ashore in Normandy on 6 June 1944, reinforced it with thousands of troops and vehicles every day, sustained it with food, petrol and ammunition, and provided everything it needed, from floating artillery support to workshops and headquarters.

D-Day forced Nazi Germany into a two-front war it could never win. It was the final, decisive triumph of Allied sea power, and brought the war in Europe to an end.

Nick Hewitt is head of collections and research at the National Museum of the Royal Navy, and the author of several works of naval history.

The single greatest factor in the Allied victory over Nazi Germany and its allies in Europe was the role that Adolf Hitler played in determining the offensives launched by the German military. On multiple occasions, Hitler’s decision­ making was flawed. While a political leader generally has an impact on his or her nation’s military engagements, Hitler frequently ignored the recommendations of his advisors, and ordered major opera­ tions that ultimately had enormous consequences and affected Germany’s ability to achieve final victory.

Hitler gave the green light to the invasion of the USSR on 20 June 1941, and the German invasion commenced two days later. Despite initial successes all along the front, the operation ground to a halt within months. Instead of easily defeating the Soviets, as predicted, the Germans woke a sleeping bear that refused to be budged from either Moscow or Stalingrad. Thousands of German soldiers surrendered or died while fighting in Moscow, Leningrad and Stalin­ grad. Like a meat grinder, the war in the east consumed millions of men. On 11 December 1941 – three days after he announced the end of the winter campaign – Hitler joined Mussolini in declaring war on the United States even though the Soviet Union had not yet been defeated

In the spring of 1943, despite the Wehrmacht’s crushing loss at Stalingrad, Hitler was still planning for Germany’s triumph. He authorised Operation Citadel, an attack against the Kursk salient that was one of the last major offensives on the eastern front, and which proved to be an unmitigated disaster. Following the Wehrmacht’s defeat in that battle, Soviet military forces

Hitler frequently ignored advice and launched major operations along the entire front began a steady push west towards Germany. By the summer of 1944, increasingly pressed by the western Allies, German forces faced challengers in Italy, France, Belgium and the Netherlands. Not willing to throw in the towel, Hitler authorised the Reich’s final counteroffensive in the west, Operation Autumn Mist – known as the battle of the Bulge – which also ended in defeat, and was the final nail in the coffin. Germany no longer had the chance of a victorious outcome. Although the Soviet, British, American and Canadian armies together defeated Germany, Hitler’s flawed decision ­making played a significant role in the Allied victory in Europe.

Mary Kathryn Barbier is professor of history at Mississippi State University and the author of Spies, Lies, and Citizenship: The Hunt for Nazi Criminals in America and Abroad (Potomac Books, 2017).

As soon as their homeland was invaded in September 1939, several Polish math­ ematicians escaped to the west with the secrets of the German ‘Enigma’ encryption device. This scrambled all 26 letters of the alphabet to a pre­set key that changed every 24 hours. From the May 1940 invasion of France onwards, German reports – essentially transmitted in Enigma gibberish – were intercepted over the air and forwarded by outstations to Bletchley Park, near Milton Keynes in Buckingham­ shire, which housed the UK Government Code and Cypher School and the intelli­ gence programme known as ‘Ultra’.

Several brilliant minds at Bletchley helped devise ‘bombes’: electromechanical devices designed to discover the daily settings of Enigma machines. From March 1940, these increased the pace that German messages could be deciphered, translated into English and assessed for their military importance. Understanding Enigma traffic contributed to victory in the Battle of Britain, assessing the German threats to invade England, and was especially important during the battle of the Atlantic, on which British survival depended in 1941–42.

Enigma provided tactical intelligence of mostly short­term value. More long­ term insights into the German military mind were gleaned from mid­1941, when senior commanders started transmitting coded orders to one another using the ‘Lorenz’ wireless teleprinter, whose traffic was nicknamed ‘Tunny’. This gave access to strategic intentions and was initially deciphered by brainpower alone, until the creation of ‘Colossus’, the world’s first programmable digital electronic computer, which commenced operations in February 1944.

It is challenging to measure the precise value of the work done at Bletchley, where Italian and Japanese traffic was also broken. We do know that on 12 July 1945, US general and future president Dwight D Eisenhower wrote a secret letter to thank Sir Stewart Menzies, who had kept both Churchill and Eisenhower supplied with daily Ultra material. In it, he stated: “The intelligence which has emanated from you before and during this campaign has been of priceless value to me... It has saved Intelligent design thousands of British and American lives, and in no small way contributed to the speed with which the enemy was routed and eventually forced to surrender.”

This was reinforced by Sir Harry Hinsley, a former Bletchley man and later author of the official volumes on British Intelligence in the Second World War. He stated that, without Ultra, “the war would have been something like two years longer, perhaps three years longer, possibly four years longer than it was”.

Peter Caddick-Adams is a military historian whose latest book is Sand and Steel: A New History → of D-Day (Arrow, 2020).

Fundamentally, the European Axis – and Japan – lost because they were much weaker than the Allied coalition. The Second World War was fought between the haves and have­nots, between established powers and ‘revisionist’ ones. To the Axis leaders, world resources – both overseas and in territories within Eurasia – had been divided up unfairly and without their participation, in the 1919 Treaty of Versailles and before. To quote the Axis Tripartite Pact of Septem­ ber 1940, it is “a prerequisite of a lasting peace that each nation of the world receive the space to which it is entitled”. They lacked these resources in 1939, and Germany faced the additional problem that the treaty had restricted its armed forces until the mid­1930s.

There is no space to discuss Italy or the smaller Axis satellites; they too had a sense of entitlement, but could never have won without Germany. Hitler believed he could deal with the estab­ lished powers by knocking them out one by one, and at the same time consolidate a blockade­proof resource base deep in Eurasia. Related to this was the Prus­ sian­German military tradition, which counted on better­led armed forces winning quick victories in ‘wars of movement’ rather than protracted wars of attrition. This failed: by late 1941 Hitler faced a situation where he could not invade Britain nor control more than the deep borderlands of the USSR. As Hitler put it in his ‘Testament’, written in a besieged Berlin in the war’s endgame: “The tragedy of the Germans is that we never have enough time.” Historically the Axis powers were late­comers, trying to catch up from a position of weakness. Because they were weak, they failed.

Evan Mawdsley is honorary professorial research fellow at the University of Glasgow and the author of The War for the Seas: A Maritime History of World War II (Yale, 2019).

This article was first published in the May 2020 edition of BBC History Magazine