The 'barrier of suspicion' that marked the beginning of the Cold War

One day in early August 1945, my father Richard Dimbleby broadcast a dispatch from the fallen German capital Berlin to the BBC in London. His words caused an uproar: "Somewhere between us and the Russians there's a barrier of suspicion... passing through the Brandenburg Gate, which marks the boundary between the British and Soviet zones of occupation in Berlin, is like crossing a frontier." He had broken a taboo by uttering an unpalatable truth.

Moscow and Washington protested vehemently while British negotiators at the Potsdam Conference - the meeting to decide Germany's post-war fate - not only rejected Dimbleby's assertion but sent a tart message to the BBC's director-general in London, warning him it would be "disastrous if our efforts to build a firm foundation of Allied unity to ensure the peace of the world were impaired by criticism in the BBC".

Yet, as every one of the Allies knew, even if none wanted to admit it openly, Stalin had not only won the war but the peace as well. Half of Europe was now at the mercy of the Soviet Union - and the dictator was starting to show his true colours. As Britain marks the 80th anniversary of VE Day, we honour those of our forebears who fought and died to save democracy, freedom and the rule of law from the tyranny of Nazism. It may seem callous, therefore, to suggest it was not so much those valiant warriors but the men and women of the Soviet Union who broke Hitler's stranglehold on Europe.

Yet - however disconcerting it may be - it was indeed the Red Army and not the Western Allies who destroyed the German armies on the battlefield and, in so doing, gave Stalin the whip hand in settling the fate of the continent for generations to come.

That victory in 1945 came at a terrible human price. Some nine million Soviet soldiers lost their lives in what the Russians call the "Great Patriotic War" - almost 10 times as many as on the Allied side. In addition, some 20 million Soviet civilians perished in the course of Hitler's crazed and fatal invasion of Russia in June 1941 in the belief he could destroy "Judaeo-Communism" and create "Lebensraum" (or living space) for his Aryan "master race".

At that point, the German High Command thought the Soviet Union would collapse within a few months, allowing Hitler to turn his attention back to Britain, the only remaining European democracy that was still free of the Nazi jackboot. The High Command in London feared exactly the same thing.

With America yet to enter the war, they hoped the titanic struggle between Europe's two most detestable regimes would last long enough to weaken them both - thereby taking some of the pressure off Britain's fight for survival. To that end, when Hitler launched Operation Barbarossa, the invasion of Russia on June 22, 1941, Churchill, who loathed communism with every fibre of his body, nonetheless publicly promised Stalin all the aid "which is in our power" to deliver, explaining privately: "If Hitler invaded Hell, I would make at least a favourable reference to the devil."

British aid and Lend-lease supplies from the United States began to trickle into Russia in the autumn of 1941. It was not enough to either arrest the Panzer blitzkrieg or to make more than a marginal impact on the Red Army's frenzied efforts to save Moscow. In those freezing winter weeks when frostbite claimed tens of thousands of German casualties, Hitler's "invincible" armies were forced into a disorderly retreat from the gates of the capital.

This was a point of no return for him, a military setback from which the Germans would never recover. From that moment on, he could squander the lives of millions of young men in a pointless war of attrition but, however fervently he might rant and rail, the Wehrmacht had lost its only chance of destroying the steadily growing might of the Red Army. That is not to forget the horror at Stalingrad in the last six months of 1942, when German morale was shattered and a growing number of generals finally realised that a full-scale withdrawal was their only realistic option.

And, in the summer of 1943, there was also the greatest tank battle in history at Kursk - the Wehrmacht's last-ditch attempt to reverse history. Despite all this, the onward march of the Red Army was unstoppable.

By January 1944, the Red Army had lost six million soldiers on the battlefield. Yet, so vast was the Soviet Union's pool of cannon fodder that Stalin could easily replace them. Thus even more than six million troops were now lined up along a front that stretched for 2,000 miles from the Baltic to the Balkans. Against this massive force, the Germans could only mount 2.5 million men, a relative disadvantage that was more than matched in armour, artillery and aircraft.

In the next five months, Stalin's forces advanced relentlessly, lifting the siege of Leningrad, retaking the Crimea in the south and liberating much of the Ukraine. But it was in June 1944, at the centre of the line, that they delivered the coup de grace, a death knell that opened the way to the German frontier long before Western Allies had even reached Paris. Stalin launched Operation Bagration on June 21, a fortnight after D-Day.

But while the Allied armies got bogged down in Northern France, the Red Army swept through Belorussia (today's Belarus). Within two weeks they had killed or captured 350,000 German soldiers - the cream of the Wehrmacht. It was the greatest defeat in any campaign ever inflicted on any German army, a body-blow from which it was quite impossible for the Wehrmacht to recover.

Poland, whose people had endured unspeakable cruelty at the hands of the Nazis, was the Red Army's next target for liberation, its advance greatly accelerated by the US-supplied Chevrolet and Chrysler trucks (which had been arriving in ever larger quantities from across the Atlantic), which made it possible for the infantry to keep up with tanks.

On August 1, with the Red Army fast approaching, the Polish Resistance staged the heroic but suicidal Warsaw Uprising against their Nazi occupiers, who had already subjected them to unspeakable cruelties. But Hitler was not yet finished. His response was to order that "every citizen of Warsaw is to be killed, including men, women and children" and that the city "be levelled to the ground in order to set a terrifying example to the rest of Europe".

Driven by the same murderous hatred, he also sent Adolf Eichmann to Budapest with orders to transport every Jew still living in the Hungarian capital to the extermination camp at Auschwitz to join the six million already slaughtered by the Nazis. Such barbarity could not stop the advance of Stalin's armies - themselves consumed by hatred and hungry for vengeance - from reaching the iron heart of the Third Reich. The Soviet advance towards Berlin had unstoppable momentum.

Some Americans would later claim that along with a huge amount of other supplies, Allied aid saved the Soviet Union from defeat. Some Russians claimed conversely that it made little or no difference. In truth, supplies from the two Western Allies played a significant but not critical role. Stalin's victory was accelerated but in due course the Soviets would have occupied Eastern Europe anyway.

Of greater strategic significance was the faith an ailing Franklin D Roosevelt chose to place in Stalin's integrity. While Churchill railed in private that "the Russians are spreading across Europe like a tide" and "drunk on victory", the US president continued to take the Soviet dictator at his word.

To the PM's horror, the Americans agreed in the spring of 1945 that the main US force would link up with its Soviet counterparts well south of the German capital rather than in Berlin itself. Delighted by this agreement, Stalin confirmed gleefully that he was in no hurry to occupy the capital either.

At once, though, he summoned his most senior generals, asking them: "Who is going to get to Berlin first?" As they knew, it was a rhetorical question. The date was April 1 - All Fools Day. In the "race to Berlin" there would be only one runner. After a bloody struggle in the streets of the city, the Red Flag was duly raised on the roof of the Reichstag on May 3, 1945, three days after Hitler had killed himself in his bunker. Five days later, on May 8, Germany formally and unconditionally surrendered.

My father stayed on in Berlin for several more weeks, sending back some 80 reports to the BBC in which he described the broken state of the capital and the terrible privations endured by so many citizens, including the surviving Jews, as they scrabbled for survival amidst the rubble.

In almost six years of war he had witnessed terrible things, not least the concentration camp at Bergen-Bergen, much of which he would hope to forget. Not though, that broadcast which so angered the Allied negotiators at Potsdam.

Stalin had got exactly what he wanted and there was nothing the West could do about it. And that was the fact neither London nor Washington wanted openly to acknowledge at Potsdam. The chill winds of the Cold War were already blowing with grim inevitability.

• Jonathan Dimbleby is the author of Barbarossa: How Hitler Lost The War; and Endgame 1944: How Stalin Won The War, both published in paperback by Penguin, priced £12.99 and £10.99 respectively