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Operation Unthinkable: Churchill’s plan for World War Three

Churchill’s top secret plan to attack the Soviet Empire was scheduled for 1 July 1945. British, US, Polish and German forces were to attempt to liberate East Germany and Poland and bring Stalin back to the conference table. If they did not succeed, Allied forces would be sucked into a Third World War. How close did Britain come to Armageddon in 1945?

Jonathan Walker is the author of Operation Unthinkable: British plans to attack The Soviet Empire 1945. He is a member of the British Commission for Military History. He is also a Vice-President of the West Country Writers’ Association and recently retired as an Honorary Research Associate at the University of Birmingham. He writes, broadcasts and lectures widely on aspects of 20th Century warfare and makes regular visits to battlefields across the world.


Good afternoon to you all, ladies and gentlemen, it’s very good to see you.

Events in Ukraine have really highlighted the whole issue of Eastern Europe, but this afternoon we’re going to look at the extraordinary plan that Churchill had to attack the Soviet Empire on the 1st July 1945 and try and claw back East Europe and Poland in the first instance.

It is amazing to think that just two months after the end of the Second World War, the world could have faced Armageddon and we’re just going to look at how close we came to that position.

The story of this astonishing plan really starts with this National Archives’ document here. It’s a folder belonging to the joint planning staff and they were tasked, during World War Two, with devising all sorts of plans. Most of their papers were released into the then Public Records Office in 1972 and this is a memorandum of some of their war plans and you’ll see we have a number here which are withdrawn.

Now when researchers first looked at this, this got them going a bit because they’d heard rumours there was an unthinkable plan; what had happened to it? And obviously it was probably one of these from the original memorandum.

Enquiries were made to the Cabinet Office who steadfastly refused to comment; they said there was no plan. Then suddenly in 1998, the plan called Operation Unthinkable suddenly appeared in the then PRO [Public Records Office] and it was reference CAB 120/691. Obviously, by then, the Cabinet Office believed with the Cold War over, that Russia was not going to be too upset with our plans to attack them.

Now the story of this plan really starts here; some of you may be familiar with it. Churchill knew this as his naughty document, he called it. And it was hatched when he was very concerned that the Red Army were going to sweep into Athens. And he had a meeting with Stalin and they’re sitting opposite each other and Churchill has this note scribbled down with percentages of influence in all the countries in Europe and he pushes it across the table to Stalin who ticks it at the top.

Interestingly enough, the one country on there which isn’t a percentage deal is Poland because Churchill wants to keep Poland relatively free and democratic, compared to a lot of these other countries.

By the time Churchill, Stalin and Roosevelt meet, The Big Three, in Yalta in February 1945, Stalin has already stitched Poland up. He has virtual control of the country, has eliminated the resistance and he was setting up a provisional, communist, pro-Soviet government.

Churchill is determined to hold out for free and fair elections in Poland but the problem he has is that Roosevelt, who is clearly a sick man, is determined to act as honest broker; he’s got no wish to upset Stalin. And this is firstly because Roosevelt is anti-imperial and he suspects that anything Churchill hatches or suggests is part of his ambition to maintain the influence of the British Empire; and secondly, Roosevelt is very keen to keep Stalin on board because he wants Soviet help to finish off Japan. And remember, at this stage of the war, war with Japan is probably going to go on until 1946. So consequently, Churchill is elbowed out.

Now as Yalta came to a close, the race was on between the US and British commanders to reach strategic targets in Germany and here we see in the Jeep, Churchill and Montgomery travelling up to the Rhine and this is six weeks before the end of the War.

Monty was keen for a single thrust to Berlin, but he was thwarted by Eisenhower, the Supreme Allied Commander, who was determined to make the industrial Ruhr the main Allied target, leaving Berlin to the Soviets. And it was this massive, threatening presence of two and a half million Soviet soldiers around Berlin that really alarmed Churchill.

During this period, Churchill constantly sends telegrams to Roosevelt, warning him about the threat from further Soviet advances. The US President, who we saw there in a very poorly state, nevertheless bluntly tells Churchill: ‘I’ve tried to make it clear to you, Winston, that while we’re your allies and in it to victory by your side, you must never get the idea that we’re in it just to help you hang on to your archaic, medieval empire’. And the other problem for the Allies, the equation between East and West, is that Roosevelt dies on the 12th April and his successor is the poker-playing farmer from Missouri, Harry Truman.

He came into the game at a critical stage not having met the principal players. But Churchill is initially delighted with Truman because he has a very tough stance towards Stalin; that is, before the American State Department get at him.

Another potential flash point between East and West is the area at the top of the Adriatic. I don’t know whether any of you have been to this area, it’s called Venezia Giulia and it’s just below the Julian Alps. In all the papers you read concerning this area, this is the point where the planners believe that World War Three might start in the closing months of the Second World War.

But the problem is you’ve got Tito and the Yugoslav communist partisans coming up this way, Alexandra and the British forces closing in here. Tito is trying to take Trieste and the fear is that if there’s a clash in this area here, Stalin will weigh in on Tito’s side and the Americans will have to support the British and it’ll all kick off.

The other flash points the Allies are concerned about are up in Austria, up through here, where the Red Army is facing Allied forces. Units of the US and Soviet armies finally meet on the 25th April 1945 at Torgau on the river Elba. Remember that during World War Two, or as the Soviets called it, the Great Patriotic War, they lost over 25 million citizens, and the country lost a third of its national wealth. In the grand scheme of things, Stalin believes that because of this sacrifice, he’s got every right to take as much European territory as a prize as he can get away with. Despite the false scenes of mutual admiration between the US and Soviet forces when they meet, there are great underlying tensions.

By the 8th May, Western forces had pushed some 150 miles beyond the Yalta agreed boundaries to a line of contact with the Soviets. So this whole pink area here the Allies take in addition to what was agreed, that was the Yalta line there, but because of the logistics they pushed onto this line here. The Americans are very keen to give it up; Churchill wants to hang onto it as a bargaining chip.

Churchill cables his Foreign Secretary, Anthony Eden: ‘The Allies must not retreat from their present positions until we are satisfied about Poland and also about the temporary character of the Russian occupation of Germany. If these problems are not settled before the US armies withdraw from Europe and the Western world folds up its war machines, there is very little prospect of preventing a Third World War.’

So there you have it in black and white.

Churchill’s other concern as the war closes, is Soviet designs on the Denmark peninsular. British forces are coming up here and just managed to close off the point here [near Lemberg] just as the Soviets arrive 12 hours later and British forces are getting, as it happened, erroneous reports that up here in Copenhagen, Soviet paratroops are landing. So there’s a very real fear in the air that the Soviet are going to press on up through Denmark and perhaps up into the Low Countries.

At this time, Churchill is getting a lot of reports about the systematic rape and destruction that’s going on around Berlin and the Soviet occupied areas. In his letters that are very wide ranging in his fears, they kept at Churchill Collage, he’s regularly talking to his political colleagues and military commanders saying how concerned he is that this system of rape and pillage is going to be carrying on throughout the whole of Eastern Europe.

Another thing the Allies are concerned about is the state of the way the Soviets are stripping out the infrastructure of the territory they occupy. This factory in Germany, the damage isn’t caused by Allied bombing, this is Soviet engineers stripping out and taking away everything which can be of service and taking it back to the Soviet Union. And this particular policy is happening very much in Poland.

The concerns we’ve looked at compelled Churchill in early May 1945, to order his chiefs to contemplate a new war with the Soviet Union. It’s quite clear that Stalin has reneged on Yalta, especially over free and fair elections in Poland. If the West could invade Eastern Germany and Poland and inflict on Stalin a crushing, short, sharp defeat, Stalin might have to rethink his domination of Eastern Europe.

But Britain had to act quickly while she still had the military force. Within months demobilisation would erode her strength and the Americans, of course, were preparing to move vast numbers of troops out to the Far East.

So the chiefs and their planners immediately start work on the top secret plan Operation Unthinkable. And the date is 1st July 1945, two months after the end of the Second World War. British planners anticipate the Americans will have to be involved, but at this stage they’re not consulted.

It’s hard to see though, from the policy of Truman and the State Department that they ever would be involved in it; they continued to see Churchill as the fly in the ointment in their dealings with Stalin. One American general though, was ready for another scrap. He needs no introduction, but I think he’s pointing the way to Moscow; he would have been up for it.

And here is the previously top secret plan, known only to Churchill, his three Chiefs of Staff and their immediate planning team. So the idea is to use a combined force of British, American, Polish, German forces to attack and defeat the Red Army and in the words of the planners: ‘The overall or political object is to impose upon Russia, the will of the United States and the British Empire’.

Tough talk indeed.

Interestingly the maps and plans were never brought into the public domain; they were either destroyed or they’re still withheld. So this is a map I’ve constructed from the, pretty detailed, movements reported in the plan. And the idea was, it would be a two-thrusted attack: northern, here, on a line from Stettin through to Bydgoszcz, curving up here and taking some of the Baltic coast. There would be Allied assaults here, coming in through here into Gdańsk; this was thought to be a fairly easy area to take. The tricky part would be the southern flank which would come up here through Cottbus, through Poznan and peel off there and take Wrocław.

The problem is that the southern flank, Czechoslovakia, it is absolutely heaving with Soviet forces and the danger is, if the Allies pushed too deep into Poland, they’d be cut off by a southern thrust from the Red Army in Czechoslovakia.

So the idea is to defeat the Red Army in this area here, and that includes defeating their armoured brigades, and then establish a line from Gdańsk right down to Wrocław; with the hope that Stalin would have had such a bloody nose he would have come back to the conference table and we might have renegotiated the borders.

Now the problem was, if we didn’t defeat the Red Army in the field decisively but got drawn further in, we would have the same fate as Hitler and before him, Napoleon; the classic clamp. The planners also believed that once we’d attacked the Red Army, Stalin would have pushed up through here, taken Norway and moved down as far as Trondheim. He would also have invaded Greece, he would have taken Turkey and come down here and taken Iraq and Iran for the oil.

At the same time, they believed that once hostilities started, Stalin would immediately ally himself with Japan; so problems on all fronts. And despite the fact that the Poles had most to gain from Unthinkable, at the time they’re kept in the dark about the plan and there appears to be no record of Operation Unthinkable in the Polish records. But their army would have been an important element and they would have proved a very formidable force because at the end of the Second World War they number about 250,000 and growing. And their ranks are continually swelled by POWs being released and also the Poles who are conscripted into the German Wehrmacht, they’re pouring back to join Anders’ army because, although they don’t know about Unthinkable, they really do believe there’s a chance of taking on the Soviet Union. And if Unthinkable did get underway, this would be a man the Allies would definitely need, General Anders.

At the end of the war he’s commanding the Second Corps in northern Italy. An implacable opponent, in many ways, of Churchill; sometimes it’s a love/hate and sometimes it’s just purely hate. Anders spent some time in Soviet prisons, so he knew all about how the mentality worked and he’s forever telling Churchill how Stalin thinks and works. Churchill, on his side, often is drawn to frustration and says, ‘we don’t need your help, you can take your divisions away; we’ll do without them’. And of course, if it did come to a war, we would have definitely have needed them. And Anders’ Army, which I said grows and grows immediately after the war, is not disbanded until 1947 because amongst Polish leaders there is still this hope that they’ll be able to claw back their territory.

Now, while Churchill weighs up the Soviet threat in May, tensions are running high in Berlin where Field Marshal Montgomery has to liaise with his Soviet counterparts seen here, Marshals Rokossovsky and Zuhkov and of course the Brandenburg in the back.

On the 14th May, just a week after VE day, Montgomery flew back to London to see Churchill and was surprised when he was ordered not to destroy any German weapons in case they were needed for a future war with the Soviet Union. So you have massive compounds of Wehrmacht equipment being guarded by British forces; artillery and even aircraft, all kept in a state of readiness, as well as a lot of German units, just in case they’re needed.

Another problem that concerned the planners was demobilisation of British and Empire troops. At VE Day, there are about five million British service men and women and their due to be demobbed and of course they’re keen to get out and get home. There’s always the spectre of being sent out to the Far East but most troops felt they had just done their job and wanted to get home. Planners were worried that if it’s delayed too much, there’ll be unrest.

But, interestingly enough, in May and June 1945, the rate slows; it’s only three thousand a day are demobbed. That, I think, is an indication from on high that people are saying, ‘Well hang on, let’s not just push this too far in case we need forces in the coming months’. Practical side was: troops who’d fought a bitter war and fought their way all up through northwest Europe, when they’d reached their target, then to be told, ‘Well hang on, in a couple of weeks we’re going to be at it again’, I cannot believe that morale would have been sustained.

Now, if the Allies did get pulled into a deeper war in Europe, if they didn’t destroy the Red Army early on but pushed on through beyond Warsaw, they’d encounter countryside like this. I know it’s a bit like Britain recently but the land beyond Warsaw is very difficult to work in; you’ve got huge swamps, large forests and mechanised brigades have their work cut out getting through it.

Now the real crunch with this plan comes over man power because the planners beaver away, working out how many divisions we’ve got, active divisions can take part, infantry and armour and looking at the Soviets. It turns out that the Soviets exceed our infantry divisions by 4:1 and in armour they’re 2:1; so huge advantage on the other side. As far as actual divisions go, the Allies could muster 47 divisions while the Soviets would manage 170 divisions.

Perhaps one of the most controversial parts of the plan was the use of German troops. After VE Day, 700,000 Wehrmacht troops are kept within military formations inside the occupation zone. Obviously disarmed but they are still kept in their units until the end of 1945; in fact, even the replacement Nazi government, presided over by Admiral Doenitz, continues in office for up to two weeks after the end of the war. But the problem is quite how the British, US and Polish forces would have reacted to operating alongside their recent enemy is hard to fathom.

Mercifully, the plan did not envisage using SS formations but since the start of the hostilities is scheduled for 1st July 1945, they don’t believe that they can re-equip and retrain the Wehrmacht to work with British and American forces until mid-summer. So they envisage that if the war drags on through the summer, at that point German forces will be used. But even then, if you’re a German infantryman and you’d served a few years out on the eastern front, you certainly wouldn’t want to return.

What about the role of the British and US air forces? Well the Allies would have had superiority over the Red Air Force, but the Allied Tactical Bomber Force would be initially hampered by having to operate from bases in England. It would take quite a few months to move bases forward into Germany, by which time, of course, the impetus would be lost.

The other big difference operating in this theatre is the sheer distance to be covered; much greater of course than into Germany in the Second World War. Now among the Allied targets would be Red Army troop concentrations, railways and river crossings, as well as the elongated Soviet lines of communication. But the Allied Air Force wouldn’t have the large number of industrial centres that were popular targets in Germany and although Soviet radar technique is inferior to the West, losses suffered by the Allied Air Force in Operation Unthinkable, could not easily be replaced. Remember we’d lost 55,000 bomber crew and that sort of experience was at a premium.

Using resources from northwest Europe and the Mediterranean, the planners reckon that we can muster 2,500 bombers. Against them, the Red Air Force could muster 3,000 bombers and a number of these would be occupied by all-female crews, known as the Night Witches.

There were about a thousand Soviet women employed as fighter or bomber pilots and many became highly decorated, but so many of the Soviet aircraft were obsolete or damaged and the Red Air Force tactical fighter aircraft were far more formidable, for the morale of the Red Air Force was very high, but they were vulnerable.

They had to import 50% of their high grade aviation spirit and if the Soviets were denied aluminium, which they had been getting throughout the war from the West, they couldn’t replace their lost aircraft. With the numbers, Allied aircraft estimated at 6,500 and Soviet fighters at 12,000, so in fighter aircraft the Soviets had a 2:1 superiority.

The Allies would also find themselves with problem behind their own lines. Much of Allied occupied Europe, Allied occupied Germany, is in disarray. Refugees, millions of them, are pouring backwards and forwards and the infrastructure is smashed. There’s also the fear of the allegiance of resistance groups in France, Italy and the Low Countries and the planners say that there are so many communists in, for example here, the Maquis, or in the Italian or Dutch resistance, that Stalin would issue orders for them to sabotage Allied operations.

What about the strength and calibre of the Soviet infantry? On 1st July 1945, the Red Army would probably number about seven million men, of whom six million are in the western theatre; in addition there’s about half a million special security or NKVD [Narodnyy Komissariat Vnutrennikh Del] troops.

For the Allies, the plus side is that Stalin’s constant purges had cleared out many of the able and educated officers. Discipline and drinking is also a problem and the average Red Army soldier was pretty exhausted by 1945. But, Soviet equipment had improved a lot during the war and they’d also captured vast quantities of German weapons, especially huge numbers of anti-tank weapons. They’d become competent tacticians, engineers and signallers, so in short, they’re a formidable enemy.

8th June 1945 and the Chiefs of Staff submit their final conclusions on Operation Unthinkable to Churchill. Mercifully, they decided that due to the huge numerical superiority of the Red Army, a short, sharp Allied attack into Poland would not succeed and that total war would be the only outcome. If the Allies were drawn into the Soviet Union itself and the horrendous winter set in, the US would weary and Western resolve would collapse. At the same time as this is happening, the British general election takes place. Although the election took place on the 5th July, because all the votes cast by troops in the Far East had to be counted, the results would not be announced until three weeks later. In the meantime, Churchill is still consumed with the threat from Stalin. After his Chiefs of Staff have turned down the original idea of attacking the Soviet Union, Churchill now turns Operation Unthinkable on its head and he says to his Chiefs, ‘look, if we can’t attack them, what will happen if the Red Army push beyond Berlin, sweep through France and into the Low Countries and try and attack Britain?’. So he gets them to work on a new plan. And while they’re calculating the odds of Britain being invaded, Churchill goes off to the Potsdam Conference and he just takes a few hours out to visit the bunker [Führerbunker]. And here he’s supposed to be…the caption on this one says he’s trying out Hitler’s chair for size. Well of course, it was any old chair they found there, I’m more than sure it wasn’t Hitler’s.

Interestingly enough, when he visits the bunker, when you think he’s coming to the lair of his archenemy, he’s not in awe or he doesn’t make any profound statements. He goes a few steps down into the bunker, where the air is very fetid, comes back up and just says to somebody, ‘Hitler must have come out here to get some air and heard the guns getting nearer and nearer’. That’s all he says and then walks off without comment.

Back into the conference, Churchill, Truman and Stalin all smiling for the camera, each one of them with, probably, with fingers crossed behind their backs. Despite the forced friendship at Potsdam, Churchill is still very concerned. After all, Stalin’s grip on power relies on the continued revolutionary struggle. The perpetual search for enemies of the people has to be carried out and its momentum has to be kept going and they really think that’s going to push him further on.

The British planners calculate that if the Red Army occupies Western Europe, they won’t attempt an amphibious landing but what they would do, would be to use German rocket technology and blast their way. Because they’d captured a lot of V2 scientists, they’d captured the V2 testing site early on at Wizna in Poland and they thought, within months of the end of the war, the planners thought, the Soviets would have the power to launch salvos of V2s at us from the Low Countries. So an immediate strengthening of Britain’s forces is ordered.

How much did Stalin know about Operation Unthinkable? Well he obviously knew the British were stockpiling German weapons and supplies and he may well have received secret British documents relating to Unthinkable, via probably, Donald Maclean, later exposed of course as one of the Cambridge spies. Maclean was First Secretary of the British Embassy in Washington at this time and we know from the Venona papers, that he did pass on to his Soviet handlers, secret telegrams between Churchill and Truman and telegrams lower down the food chain.

At the Potsdam Conference, Churchill received news of the successful US testing if an atomic device. According to his Chief of Staff, he became animated, declaring that Stalin, no longer had the West by the throat. He said, ‘If Stalin insists on doing this or that, we can just blot out Moscow, Kharkov or Kiev’.

The atomic bomb had clearly reignited Churchill’s hopes of Operation Unthinkable. The problem was, it was America who controlled the Atomic Bomb, not Britain.

The new device was to be used without delay, to force the Japanese surrender. This is Little Boy on its cradle, ready for loading onto the aircraft which will drop this bomb onto Hiroshima.

Much to everyone’s surprise the Labour party, under Clement Attlee, win a landslide victory in the British general election. For once, Stalin was stunned. He really couldn’t understand why Churchill hadn’t rigged it. But it was Attlee who now took his place alongside Truman and Stalin and although British foreign policy didn’t change radically under the new Labour government, it would be very hard to see Attlee taking this plan up – although, possibly Bevin at the back there, might have been persuaded.

So Operation Unthinkable was then, with a new government and new administration, it was put away in a bottom draw and forgotten. This is Colonel Tibbets piloting the aircraft which takes off on the 6th August 1945 to drop the first atomic bomb on Japan. The bomb detonated at six hundred meters above Hiroshima and destroyed the city. Two days later, as agreed at Yalta, Stalin declares war on Japan and invaded Manchuria to grab as much of it as he could before the Japanese surrender. That evening, a second atomic bomb was dropped on Nagasaki and within the week, Japan had surrendered. But the irony of this is, that with the atomic bomb, the US never needed the Soviet Union’s help to defeat Japan.

Had the atomic bomb been successfully tested several months before July 1945, there could have been less cause for the US to appease Stalin at Yalta and Potsdam.

With determined pressure from both Britain and the US, it’s just possible that Stalin might have pulled back from his total domination of Eastern Europe.

And I’ll finish with this slide of American servicemen and servicewomen celebrating the end of the war. They’re desperate to go home. Peace is everything and the last things on the minds of these servicemen is another conflict with the Soviet Union. But, within months, the US Chiefs of Staff were becoming alarmed at the real extent of Soviet expansion. They started work on their own plans for a war with the Soviet Union and asked for meetings with their British counterparts on how best to meet the challenge. They devise a plan called Operation Pincher which is their equivalent of Operation Unthinkable. So by 1946, Operation Unthinkable is not quite the fanciful thing it was a year before and the Cold War had really begun.

So, thank you ladies and gentlemen, I hope this talk has given you some new angles to consider and I hope that my book, Operation Unthinkable: the Third World War [], will show that while Britain and the West celebrated the end of the war, there were so many millions of people in Eastern Europe who were about to suffer another 40 years of domination. So thank you for coming.

Transcribed by Matthew Vernon as part of a volunteer project, November 2014.