How Did World War 2 Lead To The Cold War?

Decades after the official end of the (first) Cold War, many people wonder how it started. Did World War 2 cause the Cold War to begin, or was it inevitable?

The Cold War was, of course, a stalemate between the former Soviet Union and NATO countries. Both sides prepared for a major confrontation, across potentially global front lines. Their massive nuclear arsenals had more destructive potential than all of the bombs dropped during WW2. Fortunately a direct shooting war (i.e. a ‘hot war’) never began between these adversaries, but their cold, paranoid readiness to destroy whole cities at a stroke if pushed, placed the entire world at the brink of destruction.

Churchill, Roosevelt and Stalin at Yalta
(public domain)

And yet Russia and the Western Allies had fought alongside each other during WW2, eventually defeating Nazi Germany. So how could they so quickly have become such fierce enemies?

The seeds of mistrust had been sown between them long before that war, and then reinforced as the war progressed. So what is it that had happened, in such a profound way, that these vast military alliances could become such mortal enemies only years later?

Between them, the two World Wars re-wrote the rule book about what nation states found acceptable in warfare.

Atrocities have always occurred in war and civilians have frequently suffered. Take two examples:

  • … in 332 BCE Alexander ‘the Great’ crucified 2,000 Tyrians after the defeat of the city of Tyre. Another 30,000 civilians were sold into slavery.
  • … or how about the rampaging attacks of Attila the Hun’s armies (circa 434 – 451), which were synonymous with the sacking of cities, brutal torture, rapes and savagery.
Loading bombs onto a Vickers Wellington

However, mass production and the use of assembly lines meant that by 1914 the scale of killing and destruction in warfare could be taken to a whole new level (1). The degree of death and destruction during the two World Wars was unprecedented in the history of warfare. Fighting changed from limited numbers of soldiers facing each other across a defined battlefield, to strategic conflicts in which tens of thousands could die across frontlines spanning thousands of miles. These wars normalised the idea that non-combatant civilians could be freely attacked, and eventually that whole cities of millions of civilians could now be destroyed in seconds.

Ruins of a bombed city

About 40 million people were killed or wounded during WWI. Beginning just twenty one years later, a further 70-85 million people are estimated to have been killed in WW2, and about 40 million of those were civilians.

The so-called “rules of war” had been largely defined by the Geneva Conventions (2), but specific provisions for protecting civilians were not created until 1949. However, at the start of World War 2, it did seem that civilians were intended to be protected from harm as much as possible.

On September 1st 1939, President Roosevelt sent an “… urgent appeal to every Government which may be engaged in hostilities publicly to affirm its determination that its armed forces shall in no event, and under no circumstances, undertake the bombardment from the air of civilian populations or of unfortified cities, upon the understanding that these same rules of warfare will be scrupulously observed by all of their opponents(3).

Previously, in 1938 British Prime Minister Neville Chamberlain had told Parliament that “… it is against international law to bomb civilians as such(4).

Britain agreed to Roosevelt’s appeal on September 2nd, saying that the British and French had “… a firm desire to spare the civilian population(5). Germany agreed shortly afterwards.

Those commitments did not last long.

Soon Germany was bombing London and other cities during The Blitz.

Britain retaliated with increasing numbers of bombers attacking “strategic” targets in Germany, later to be joined in that campaign by the United States air force (USAAF).

Facing blitzkrieg on the land, U-boat wolf packs on the seas, and bombing from the air – all by an enemy who seemed fanatically focussed on creating its Third Reich and dominating Europe – the countries captured or threatened by Nazi Germany faced an existential crisis. What actions might those countries not take to resist or defend themselves?

WW2 was a global, Total War – it normalised the idea that perhaps almost anything was permissible…

… and that anything included the total destruction of cities as a strategic warfare goal.

One estimate is that the Allies dropped around 3.4 million tons of bombs during WW2. Many civilians were killed in ‘strategic bombing’ attacks on “… railways, harbours, cities, workers’ and civilian housing, and industrial districts in enemy territory…” (6). Hundreds, sometimes thousands of civilians would have been living and working in these areas – their deaths were unavoidable, inevitable.

The leaders of Bomber Command were increasingly seeking to determine how the maximum amount of damage could be wrought in a ‘raid’, or series of raids.

Mass bomber raid on Cologne – official war art by W. Krogman
(public domain)

If the right conditions prevailed they would be able to trigger a ‘firestorm’ (feuersturm) that could devastate a whole city in a single raid. In July 1943 they achieved this during an attack on Hamburg which saw over 2,300 tonnes of bombs dropped on the city. It is estimated that 34,000 – 43,000 people were killed in a truly barbaric manner (7).

In 1943 the British theoretical physicist Freeman Dyson was working “in the Operational Research Section (ORS) of RAF Bomber Command… developing analytical methods for calculating the ideal density for bomber formations…” (8). In his Weapons and Hope (New York: HarperCollins, 1984 – p117) and Disturbing the Universe (New York: Harper & Row, 1979- p28) he makes it clear that the intention to destroy German cities in this manner was deliberate:

… Nobody understands to this day why or how fire storms begin. In every big raid we tried to raise a fire storm, but we succeeded only twice, once in Hamburg and once two years later in Dresden…

The Hamburg firestorm was in many ways comparable to the nuclear attacks that Japan would soon see:

… concentrated, unchecked fires linked up to turn parts of Hamburg into a furnace. Hot air soared into the sky, sucking more from street level… temperatures reached at least 800C. Wood, fabric and flesh blazed. Glass exploded, metal twisted, stonework glowed dull red… streets became tunnels of screaming hurricane-force winds. One survivor recalled a noise ‘like an old church organ when someone is playing all the notes at once.”(7)

Two years later another firestorm was triggered when over 3,900 tonnes of bombs were dropped on Dresden. An estimated 25,000 people were killed in that attack (9).

The fight against Nazi Germany had normalised the killing of whole civilian populations during a war, including the total destruction of cities for ‘strategic purposes’.

Nobody had been safe – fighting could rapidly spread into previously unaffected areas, cities were freely attacked, with survivors and refugees then being left to fend for themselves.

German armed forces unconditionally surrendered to the Allies in Reims on 7th May 1945, just before America was ready to use its new atomic bomb.

America was destined to emerge from the war as the predominant global superpower… and, for a while, no other nation would have the finances or technical ‘know how’ to stand against them.

The decisions and actions leading to the atomic bombing of Hiroshima and Nagasaki were tragic and significant factors leading to the Cold War.

American soldiers were still dying in a brutal battle against the Japanese in the Pacific theatre. With the norm of not deliberately harming civilians discarded, the path towards the atomic bombing of Hiroshima and Nagasaki was clear, perhaps inevitable?

Britain was on its knees with debts to the US and Canada which then took 61 years to repay (10). Much of Europe was in ruins and Germany was imploding.

Meanwhile, being a long way from the frontline European areas, the American economy was booming towards full employment. It had been able to develop a vibrant wartime industrial economy which would soon evolve into a ‘Military-Industrial Complex’ (11). The vested interests of the military, politicians and private corporations created structures that fed vast quantities of materiel into the military supply chain, generating huge investments and profits, and creating all the infrastructure needed to complete the Manhattan Project.

The first atomic bomb – used in the ‘Trinity’ test, 1945

Costing about $28 billion in today’s money, it had needed the simultaneous solving of theoretical physics problems (without the aid of modern computers), engineering solutions for an actual bomb (the ‘gadget’) and the development of industrial-scale chemical processes for enriching uranium and plutonium at sites like Oak Ridge and Hanford. At this point in the war, only the vast science-technical-industrial base of the US stood a chance of completing the Manhattan Project and developing an atomic bomb.

But by late July – early August 1945, the Japanese were trying to negotiate a surrender.

We know from a 10th August 1945 communique between Mr. Max Grässli, the Chargé d’ Affaires ad interim of Switzerland, and James F. Byrnes, the US Secretary of State, that they had approached the ‘Soviet government’ several weeks previously to help them negotiate a surrender in line with the 26th July Potsdam declaration. Their only request was that their Emperor should remain as their ‘sovereign ruler’ (12). Nothing came of that approach – everything was now leading towards the first wholesale slaughter of a city with a nuclear weapon.

On 24th July, during the Allies’ conference at Potsdam, President Truman told Stalin that the US now had “… a new weapon of unusual destructive force(13)

According to Truman and Churchill, Stalin seemed to not be overly interested in this news, other than hoping “… we would make “good use of it against the Japanese…” They concluded that Stalin had no special knowledge about the vast research that had gone into the Manhattan Project. This research was not being freely shared with Russia and despite “the enemy of my enemy being my friend”, Stalin must have clearly perceived the lack of trust between him and the other Allied leaders.

Details of the Manhattan Project had in fact been obtained by spies working for Russia, including Morris Cohen, Klaus Fuchs and Theodore Hall (14). Soviet Marshal Georgii Zhukov later said that Stalin pretended to take no special interest in this news, and when he discussed it later with Molotov, it became clear that Russia was already working on its own atomic bomb project (13).

Having invested so much money in the Manhattan Project, what would it have taken for ‘the bomb’ not to be used?

Politically, it may have been impossible for Truman to accept anything other than an unconditional surrender by Japan after Pearl Harbor and the deaths of so many American soldiers in the Pacific Theatre. Roosevelt had said after the attack on Pearl Harbor, that “… we will not only defend ourselves to the uttermost but will make it very certain that this form of treachery shall never again endanger us(15).

At 08:15 on 6th August 1945, the US ‘Enola Gay’ B-29 Superfortress bomber dropped the ‘Little Boy‘ bomb on Hiroshima. Weighing 4.6 tons, it fell for 53 seconds before exploding with a yield equivalent to 15 kilotons of TNT.

The ‘Enola Gay’ bomber

The city was devastated. Approximately 80,000 people were killed immediately in the blast and ensuing firestorm. Tens of thousands more would die afterwards from exposure to radiation (16).

Hiroshima after the atomic bombing by the Enola Gay

The mass slaughter of civilians continued when, on 9th August 1945, the US bomber ‘Bockscar’ dropped the ‘Fat Man‘ bomb on Nagasaki. Weighing 5.1 tons, it exploded with an equivalent yield of 21 kilotons of TNT. Approximately 40,000 people died immediately, and another 30,000 by the end of 1945.

On 14th August Japan signalled that it would accept America’s terms, and formally surrendered to General MacArthur aboard the USS Missouri on 2nd September.

WW2 was over – so what are the reasons why the Cold War started so soon afterwards?

As the war finished, differences between the former Allies were already laying down the roots for the Cold War that was to follow.

Governments quickly understood that the atomic bombing of Hiroshima and Nagasaki had changed the world forever.

How could any State protect its citizens from the terrible destructive power of these new nuclear weapons?

And how safe were they in a world where only America had that technology, particularly when ideological differences between ‘The West’ (capitalist democracies) and the USSR (communist totalitarianism) had already driven a huge wedge between them. Suspicion, mistrust and fear became driving forces in the politics of both blocs.

America was triumphant and determined to remain the dominant global superpower, initially reneging on an agreement to share its nuclear secrets with Britain, which had merged its own Tube Alloys research work into the American Manhattan Project in 1943. But this American technological dominance was built on a foundation of insecurity after the attack on Pearl Harbor on 7th December 1941 – its leaders could never again leave a defence vulnerability like that unmitigated. Becoming unassailable meant having an unassailable nuclear arsenal. This would both enable the US to deter attacks and use the threat of those weapons to force other states to accept its foreign policy goals.

Russia was driven to secure its borders within a huge buffer zone, in order to protect itself from future invasions. How could it not remember Napoleon’s invasion of 1812, or the loss of Ukraine, Belarus and the Baltic States to Germany in WWI, or the Allies sending soldiers to fight against the Bolsheviks in the Russian Revolution, or the ferocity of Germany’s blitzkreig during Operation Barbarossa in 1941? How could it not feel threatened by the nuclear secrets that the Allies were not sharing about weapons that could destroy whole cities? Russia then successfully tested its first atomic bomb in 1949, and its first hydrogen bomb in 1953 (RDS-6).

Britain’s ‘days of Empire’ were nearly over and its position as a major global superpower was finished in all but name. The Empire was slowly contracting and it urgently needed to earn currency. Yet, with America withholding nuclear technology, and in order to stay seated ‘at the top table’, Britain felt forced to invest money desperately needed for rebuilding into its own nuclear bomb project. At enormous cost, it successfully tested an atomic bomb in October 1952 (Operation Hurricane) and a fusion-type hydrogen bomb in November 1957.

Much of Europe needed to rebuild and the continent was now split by the Iron Curtain that Churchill defined in his speech at Westminster College in Fulton, Missouri on March 5, 1946 (17).

Berlin was an uncomfortable potential flashpoint between East and West. The declaration of East Germany as the German Democratic Republic in 1949 was not recognised by the West, and espionage was becoming the next battlefield, with Vienna as an initial key focal point.

Cold War and Nuclear Weapons
All sides hid the truth about nuclear weapons from their general populations, fearing that their weapons policies would be rejected. People knew that conventional bombing raids, involving hundreds of aircraft, had totally destroyed Hamburg and Dresden. They slowly became aware that nuclear weapons could destroy entire cities with a single bomb dropped from a single aircraft, but the full details were suppressed and State propaganda about nuclear weapons began.

‘Castle Romeo’ test, 1954 – 11 Mt yield.

As both East and West lost clarity about each other’s intentions, suspicions and guesses came to shape defence policies.

With both sides now possessing fusion bombs, the risk of a superpower confrontation to the survival of billions cannot be underestimated.

The Cold War had truly started and no end seemed to be in sight.


1 – “The industrialisation of war: lessons from World War I” –

2 – “Geneva Conventions” –

3 – Foreign Relations of the United States Diplomatic Papers, 1939, General, Volume I – telegram –

Washington, September 1, 1939—5 a.m. 744. –

4 – House of Commons statement by Prime Minister Neville Chamberlain – Hansard, vol 337, col 937

5 – “conduct hostilities with a firm desire” John Finnis, et al., Nuclear Deterrence, Morality and Realism (New York: Oxford University Press, 1987), 39.

6 – “Strategic bombing during World War II” –

7 – “Operation Gomorrah: Firestorm created ‘Germany’s Nagasaki’” – BBC News –

8 – “Freeman Dyson” –

9 – “Bombing of Dresden in World War II” –

10 – “UK settles WWII debts to allies” –

11 – “Military–industrial complex” –

12 – “Japan’s Surrender Communiqués” –

13 – “Truman Tells Stalin, July 24, 1945” –

14 – has 3 references:

  1. “Atomic spies” –

  2. “Spies Who Spilled Atomic Bomb Secrets” –

  3. “Atomic Spies” –

15 – “The President Requests War Declaration 125 (December 7, 1941)” –

15 – “Bombing of Hiroshima and Nagasaki“ –

16 – “Winston Churchill’s Iron Curtain Speech” –

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: