As the American president Truman cruised towards northern Europe, an exhausted Churchill took the opportunity of a few days rest after the election and a chance to refresh himself before Potsdam. He and his wife, Clementine, stayed at the Château de Bordaberry, overlooking the Bay of Biscay in south-west France, painting and swimming, or, more accurately, floating. Churchill’s private secretary, Jock Colville, recorded in his diary that ‘the Prime Minister floated, like a benevolent hippo, in the middle of a large circle of protective French policemen who had duly donned bathing-suits for the purpose.’ When he was not bathing, Churchill painted coastal scenes at St Jean-de-Luz and Hendaye, using rich colours from his paint box to depict the dramatic Atlantic seashore.
Meanwhile, on 11 July, as the prime minister enjoyed a brief moment of relaxation in France, his chiefs of staff in London received their first glimpse of the second report on Operation Unthinkable. It had taken a month for the same JPS team of Grantham, Thompson and Dawson to report back on ‘what measures would be required to ensure the security of the British Isles in the event of war with Russia in the near future’. It was, of course, highly sensitive, even by the standards of national security and the normal staffs in the services ministries were not consulted. The premise was quite conceivable, for one of Stalin’s cherished ambitions was to control a unified greater Germany, and his Red Army might not stop at the Rhine. The report, however, assumed that the Red Army had overrun the whole of Western Europe and were poised to attack Britain, but there was no discussion as to how quickly and by what method the Soviets would conquer Europe.
There would have been some warning of a Soviet invasion, hopefully via British Intelligence, but the job of gathering intelligence on Red Army dispositions was never straightforward. Extracting information from German intelligence officers about Soviet movements caused a crisis of conscience for senior British intelligence officers, such as Dick White. ‘I would have objected to the use of a Nazi as an agent,’ he curtly noted, but ‘the prospect never arose.’ The Americans, however, had no such qualms and were not only using German Abwehr officers, but were even ‘pinching’ British agents. Britain’s pre-eminent place in the world of espionage was slipping, as was the relationship between the British and US intelligence services. The British Embassy in Moscow was obviously a conduit for local intelligence and debate about Soviet intentions. Staff spent endless hours poring over the Soviet press, such as Pravda, Izvestia or the English-language Moscow Evening News, as well as any number of technical journals for information about the strength of Soviet armaments. Then there were diplomatic trips to Kiev or Leningrad during April and May 1945, when the presence of the NKVD was not quite as claustrophobic as it would shortly become. There were gaps and opportunities, through which diplomats could talk to local people or glimpse ‘off limits’ areas.
Even if the West had some prior notice of a Soviet attack, it would only take the Red Army weeks to arrive on the French border. But what were the constraints on the Soviet operations? One major problem for the Red Army would be their long lines of communication, and once they had pushed their vast ‘Front’ units out of Eastern Europe they would no longer find themselves a majority force in their occupied territories, such as Poland, Ukraine and Germany. Resistance fighters in those countries could rise up in significant numbers and cause serious problems behind the Soviet lines.
Nonetheless, the planners opened their report with the blunt scenario:
The following are the main methods by which the Russians might attempt to attack the British Isles after they had reached the shores of the North Sea and Atlantic:
– By cutting our sea communications
– By invasion
– By air attack
– By rocket or other new methods
It was believed that the Soviets were unable to mount a submarine or air attack on Allied shipping, at least nowhere near the capability of the German threat in the Second World War. Reassuringly, it would take some years for Soviet technology to catch up, especially in submarine design. So, if the Soviets could not cut British sea communications, could they launch a successful invasion of Britain? They were unlikely to rely just on airborne operations and if they came ashore by landing craft, they would need to land in very large numbers to establish a beachhead. But the Soviets would be severely handicapped by their inexperience in such amphibious operations, and, having little or no merchant navy of their own, they could hardly support them. Most Allied merchant shipping would have been already withdrawn from Atlantic ports or otherwise scuttled in advance of the approaching Red Army; the threat of an invasion was always present but because of Soviet limitations the planners decided that the threat of invasion was not imminent.
Being overwhelmed by the Red Air Force was another possibility. Although their strategic bomber force was not rated by British advisors, the flying distance from coastal air bases in France or the Low Countries to Britain was short enough to bring industrial and military targets within easy range. Although Soviet tactical bombers were normally trained to support land operations, they could easily adapt for such an important mission and their sheer numbers could pose a threat. The RAF could expect to inflict very heavy losses on the Red Air Force, but its victory was by no means assured. However, it was the prospect of an attack by rockets or pilotless aircraft that posed the most concern:
The Russians are likely to begin large scale production of these weapons at an early date. We must expect a far heavier scale of attack than the Germans were able to develop, and we do not at present see any method of effectively reducing this. This would be the main threat over the considerable period which must elapse before the Russians can contemplate any attempt at invasion.
The planners were right to acknowledge this menace from the new weapons, for the Soviets were racing to develop copies of the German V–2, as well as ‘pilotless aircraft’. But fortunately for the Allies, they were some way from manufacturing large rockets capable of crossing the Channel. It was true that they had acquired detailed plans and operational knowledge of the V–2 rocket when their forces overran the Blizna testing ground in south-east Poland in August 1944. They were also due to receive the captured V–2 plant at Nordhausen from the Americans on 1 July 1945 (ironically the same date as Unthinkable had been due to start). But even then, the Soviets still did not possess any stocks of captured, complete V–2 rockets and neither did they have the services of enough German scientists. They did manage to secure some, but they were not even communist sympathisers. Helmut Gröttrup, a former assistant to the director of the Guidance, Control and Telemetry Laboratory at Peenemünde, had other motives, as his wife later confided:
They [the Americans] grabbed Wernher von Braun, Hüter, Schilling, Steinhoff, Gröttrup and other leading rocket experts. We were housed at Witzenhausen and interrogated. After weeks had passed, Helmut was handed a contract offering him a transfer to the USA without his family, a contract terminable by one signatory only: the US Army. Since we wanted to remain in Germany, we moved back to the Russian Zone.
It would be another year before scientists such as Gröttrup could begin to turn out Soviet V–2 rockets in sufficient quantity to endanger the West. The planners did not detail the type of rockets that posed a threat, but it would not come from the smaller Katyusha type. After all, the closest distance between France and England was 26 miles and the most powerful existing rocket, the M–13 DD, only had a range of 7 miles. However, if the rocket threat materialised any earlier, the main British defence would depend on anti-aircraft batteries, rather than the RAF – at least as far as Churchill was concerned. He had already attacked Sir Archibald Sinclair over claims that it was the RAF which had defeated the V-weapons:
You have no grounds to claim that the RAF frustrated the attacks by the V weapons. The RAF took their part, but in my opinion, their effort ranks definitely below that of the AA Artillery and still further below the achievements of the Army in clearing out all the establishments in the Pas de Calais. As to the V2, nothing has been done or can be done by the RAF.
To reduce the threat from rockets, the possibility of retaining bridgeheads on the continent was considered. By holding on to coastal areas, the idea was to deprive the Red Army of launch sites. If they had to fire rockets from further inland, aimed at London, it would be beyond the range of a V–2 type. But it was out of the question to expect an Allied army to hold on to a continual stretch of continental coastline in the face of such massive enemy forces. However, peninsulas such as Cherbourg or Brittany could be considered, along with Denmark or Western Holland, though concentrating Allied troops in these compact areas would provide the enemy with an easy target. In the end, the planners came down against establishing bridgeheads for the following reasons:
The range of the present rocket would necessitate the holding of a continuous front well into France and the Low Countries, if the scale of attack by this method is to be seriously affected.
If used as bases for a return to the continent, we should be sacrificing surprise and would enable the enemy to build up against us at leisure.
Except in the case of Denmark, use of which is limited by way of lack of harbours on the north and west coasts, the air forces we could station in the bridgehead would be little greater than those required to support the troops defending it.
Rockets were obviously an insoluble problem for the planners, who were more comfortable with the idea of conventional warfare and planning for the possibility of the Red Army sitting in captured French fortifications across the Channel. How would British commanders deploy their forces to defend the homeland? There would be the risk of a Soviet airborne invasion or amphibious landings, or both, and there would have to be mobile British units to deal with these threats – garrisons would need to be sent to defend urban and industrial centres, as well as ports. As for the defence of the rest of the country, that would be in the hands of some twenty British and US infantry and armoured divisions, deployed south of a line between the Severn and the Wash, with a concentration in the south-east of the country. The bulk of these forces were already in Britain, but they would have to be supplemented by troops withdrawing from Europe in the face of a Soviet advance. The speed of the retreat on the continent would mean a lot of their heavy equipment would be left behind. Indeed, the loss of equipment and the ability of British industry to replace it and keep its forces continually supplied would require industrial capacity to be substantially raised.
There was no reference in the plan to the possibility of an actual Soviet occupation of the British mainland, or indeed the provisions to set up a British government-in-exile in somewhere such as Canada, Newfoundland or South Africa. There was some reassurance, however, that the Royal Navy and RAF would provide a safe cordon around the country, with the local naval forces guarding the southern and eastern approaches and the Home Fleet protecting the northern waters. Depending on how the Soviet threat developed, convoy escorts would be required at a later date.
If the planners had unbounded faith in the Royal Navy, they had even more confidence in the ability of the Royal Air Force to deal with the Red Air Force, but only if both RAF and USAAF squadrons could be recalled from Europe in time to operate from British bases. To this end, RAF aircraft and personnel would be held back from deployment in the Far East, though the effect this would have on the continuing war against Japan was not calculated. Even if these conditions were met, the combined Anglo-American air force would need to muster 230 fighter squadrons, 100 tactical bomber and 200 heavy bomber squadrons.
The planners concluded:
It is only by the use of rockets and other new weapons that the Russians could develop any serious threat to the security of this country in the initial stages. Invasion or a serious attack upon our sea communications could only be undertaken after a period of preparation which must last some years.
While the chiefs of staff contemplated the JPS report, Churchill continued his long-overdue break in France, pending the start of the Potsdam Conference. ‘I’m going to relax completely,’ he informed his doctor. ‘I’m not going to look at any papers.’ It was clear he was not going to digest any government documents, and that included any new papers on Operation Unthinkable. They would have to wait. On 15 July, without returning to London, he flew from Bordeaux to Berlin for the beginning of the Potsdam conference.
Churchill invited Attlee to join him at Potsdam, pending the results of the British general election and Attlee flew out to the conference on 15 July, much to the surprise of the Soviet delegation, who could not understand why the leader of the opposition party should be included. By the time of the conference Allied troops had been withdrawn to the agreed zones, and Eden, as foreign secretary, was preparing to ‘tie up the loose ends’ of the Polish machination. Although Churchill remained depressed at not achieving his goal over Poland, he entered the conference room at Potsdam knowing that the Allies still had a major card to play – a card that could change the whole strategic balance.
Even before the first atomic test in July, the British had given their consent in principle to its use against the Japanese. Churchill confirmed that support for the bomb was emphatic:
The historic fact remains, and must be judged in the after-time, that the decision whether or not to use the atomic bomb to compel the surrender of Japan was never an issue. There was unanimous, automatic, unquestioned agreement around our table.
Truman entered the rooms at the Cecilienhof Palace in Potsdam fully briefed about the impending Trinity atomic test. The conference was due to start on 16 July, but Stalin had suffered a minor heart attack and the start of business was rescheduled for the following day. It was no wonder then that Major-General Leslie Hollis remarked ‘in the eighteen months since I first saw him [Stalin] at Teheran, his hair had gone as white as the tunic he wore.’ Churchill used the spare day to visit Berlin and the ruins of the Reich Chancellery. Lord Moran, who accompanied the PM, noted that Churchill was strangely unmoved by the surroundings. He was not even excited by the prospect of seeing the entrance to the bunker and the scene of the last sordid days of his bitter enemy. He took a few steps down into the bunker and promptly came back up into the ruined gardens. ‘Hitler must have come out here to get some air,’ he ventured, ‘and heard the guns getting nearer and nearer.’
A battered chair, hastily rescued from the bunker, was brought forward for a photo opportunity, and the prime minister dutifully sat down. ‘Churchill tries out Hitler’s chair for size’, trumpeted the subsequent headlines, but there was little triumph in Churchill’s demeanour. He was, no doubt, thinking of the forthcoming meetings and his first real discussions with Truman. He had met the president fleetingly before and had spoken to him on the telephone, but this was the first time they had met as world leaders. The PM was impressed with Truman but the feelings were not entirely mutual. ‘I’m sure we can get along,’ Truman cautiously noted in his diary, ‘if he doesn’t try to give me too much soft soap.’ When Truman finally met Stalin the following day, he had no such reservations about the Soviet leader. ‘I can deal with Stalin. He is honest – but smart as hell.’ Some of Stalin’s pronouncements certainly chimed with Truman, especially when he mentioned he would like to divide up some of the old colonies and mandates.
Business got underway quickly, despite the constant interruptions caused by delegates leaving the meeting rooms – diarrhoea was rampant, due to pollution of the local water supply – while the main concern of three British chiefs of staff was the plague of mosquitos ever present around their lakeside villa. Brooke, Portal and Cunningham made time for the odd spot of recreation, though the British chiefs were disappointed to be told that the nearby Lake Griebnitzsee was polluted by dead bodies and the fish had been blown up by hand grenades. Nevertheless, the Chief of the Imperial General Staff could still be seen in a canoe, with fishing rod in hand, being paddled around the lake by the Marshal of the RAF.
As the delegates prepared for their meetings, 6,000 miles away in a small military installation in the Jornada de Muerto desert in southern New Mexico, US scientists were about to experiment with a world-changing weapon. Just before dawn on 16 July, a truck arrived at the site bearing an innocuous-looking metal sphere. The ball looked simple enough, and, with a radius of 4ft 6in, it very much resembled a sea mine. The 4-ton load was hoisted off the truck and placed on the ground. Then, with due reverence, a canopy was placed over it, allowing technicians to adjust the device in complete and sterile privacy. The ball was then raised high up into a gantry, some 100ft above the ground. At precisely 5.29 a.m., ‘Fat Man’ was detonated. The plutonium bomb vaporised the gantry and eliminated all desert life within half a mile. Equivalent to the result of using 20 kilotons of TNT, the blast created an ‘oven heat’ that was felt 10 miles away, and its searing light was sufficient to cause temporary blindness at that distance. J. Robert Oppenheimer, the scientific director of the Manhattan Project tasked with developing the atomic bomb, solemnly witnessed the Trinity test explosion:
We knew the world would not be the same. A few people laughed. A few people cried. Most people were silent. I remembered the line from the Hindu scripture, ‘Now I am become Death, the destroyer of worlds’. I suppose we all thought that, one way or another.
On 18 July Truman informed Churchill about the results of the atomic test. Before he had left for Potsdam, Churchill had asked Truman to cable him as soon as the news came through as to ‘whether it is a flop or a plop’. The telegram read ‘It’s a plop. Truman.’ At Churchill’s request the president held off from telling Stalin until 24 July. Even then Stalin did not seem to be particularly impressed or surprised at the news. There is no doubt that he knew of the progress of the US Manhattan Project through such spies as Klaus Fuchs, whose information was ‘of great value’ to the Soviets and was later exposed in the Venona transcripts. Stalin would also have been familiar with the earlier Anglo-American atomic co-operation, known as the Tube Alloys project, from Soviet agents inside Whitehall, London. However, he may not have understood the full implications until the bomb was dropped on Hiroshima several weeks later. Only then did Stalin and Beria break into a gallop with the development of a Soviet nuclear programme.
The explosion of an atomic bomb was also another massive jolt to Stalin’s view of his future relations with the West. Together with Roosevelt’s death, in April 1945, these two seismic changes in the international landscape reawakened Stalin’s ‘old demons of insecurity’. He would now have to deal with a material shift in the balance of military power, as well as a new host of diplomatic figures, including, shortly, a change in the British leadership. Such insecurity was also felt by Stalin’s colleagues. Yuli Khariton, one of the early Soviet atomic designers, gloomily concluded that ‘the Soviet Government interpreted Hiroshima as atomic blackmail against the USSR, as a threat to unleash a new, even more terrible and devastating war.’ The Soviets were now well aware that the USAAF was capable of delivering atomic bombs, from their bases in Europe and the Middle East, to the very heart of Stalin’s empire. The bomb also hammered home to Stalin that if Japan quickly capitulated, he could swiftly lose his chance to enact the Yalta agreement and capture strategic territory around Manchuria and Japan and thereby improve his security in the east.
News on 16 July that the plutonium-based bomb was successful meant that the Americans might not need to worry about pushing the Soviets to enter the war against Japan – could they now finish off Japan on their own? At this stage the US military did not think that atomic bombs could ensure victory on their own, but would instead be a powerful addition to the mix of bombardment necessary to support the land invasion of Japan in the autumn of 1945. A much simpler uranium bomb, known as ‘Little Boy’, was also being developed, though this would not require a test explosion. Even so, little was known about the effect of radiation, and army commanders even discussed using the bombs tactically to soften up beach defences around the Japanese mainland.
The success of the Trinity test theoretically released the West from the obligation of courting Stalin and should have freed them to take a hard line with him over Poland and the other occupied Eastern European states. According to Field Marshal Sir Alan Brooke, Churchill was jubilant about the new bomb:
He had absorbed all the minor American exaggerations and as a result was completely carried away. It was now no longer necessary for the Russians to come into the Japanese War, the new explosive alone was sufficient to settle the matter! … Furthermore, we now had something in our hands which would redress the balance with the Russians.
The Potsdam leaders issued a final ultimatum for a Japanese surrender, but this was swiftly rejected by the Japanese prime minister, who announced that his forces would fight on. He was secretly trying to obtain a peace agreement with the Chinese, so that large numbers of Japanese troops could be released for the defence of the Home Islands. The Japanese military were hell-bent on continuing the war, but US decrypts of telegrams revealed that some Japanese politicians were looking for someone to broker a peace deal with the Allies. They were in a minority, so the US bombing onslaught against the Japanese mainland and islands continued. Raids by up to 500 Superfortresses and 1,000 carrier aircraft blitzed Tokyo, Nagoya, Yokohama, Osaka and Kobe, together with numerous oil refineries and ports.