Jubilation trumped reflection in Potsdam, where Truman had arrived on 15 July. Truman had agreed to the summit with reluctance, nervous as he was during his first summer as president that Stalin and, to a lesser extent, Churchill, would outmaneuver or bully him. (‘I’m on my way to the high executioner,’ Truman wrote glumly to his wife, Bess.) He knew that the Trinity test was imminent, and he held out hope for its decisiveness. But he nevertheless came to Potsdam expecting to need the Russians’ help to finish off Japan. And, though it is often forgotten now, and particularly by authors of books about the atomic bomb, Truman not only played the endgame of the Pacific War at Potsdam but confronted a host of issues on which he anticipated Soviet troublemaking: the amount and direction of German reparations, the vexed and ongoing question of the new German-Polish border, and whether the United States and Great Britain would extend diplomatic recognition to the Soviet-liberated states of Finland, Bulgaria, Romania, and Hungary, all of which seemed to be falling under Moscow’s control. Japan was much on Truman’s mind as he and his delegation— Byrnes, aide William Leahy, and Soviet expert Charles Bohlen—took up residence in a three-storey yellow stucco building at No. 2 Kaiserstrasse. But the Soviets were in his face.49
Byrnes had excluded Stimson from the entourage, seeking to assert his own control over the President and suspecting that the old man had grown soft. The Secretary of State for all of two weeks, Byrnes had from the start clung fast to the doctrine of unconditional surrender and hoped very much to avoid sharing information with the Soviets about the atomic bomb. Other advisers, including Stimson, who had invited himself to Germany despite his exclusion from the formal delegation, wanted to warn the Japanese explicitly about their imminent destruction, sweetening the threat with a promise that Japan could retain the emperor in a constitutional monarchy if it surrendered. This need not be construed as a shift away from unconditional surrender but a redefinition of it. It was Stimson who brought news of the Trinity test to Kaiserstrasse on the evening of 16 July, delighting Truman and Byrnes. When the Secretary of War returned the next day with further details of the shot, he also proposed an early warning to the Japanese. Byrnes brushed the suggestion aside and instead described a ‘timetable’ for using the bomb, and, when Truman failed to intercede, Stimson concluded that the President had already adopted Byrnes’s position. Byrnes subsequently informed his department that neither the early warning nor a guarantee of the emperor would be forthcoming.
Truman had his first meeting with Stalin that same day. After apologizing for arriving in Potsdam a day later than expected—he had been ill, and had been negotiating with the Chinese—Stalin raised a number of issues, and declared that his armies would be ready to go to war with Japan by mid-August, providing an agreement on territorial concessions could be reached with the Chinese. The meeting lasted two hours. Afterwards, Truman seemed satisfied, recording in his diary that Stalin was ‘honest— but smart as hell’, and a man he could ‘deal with’. Still not altogether sure of the magnitude of the Trinity test, the President appeared pleased to have Stalin’s pledge of help: ‘FiniJaps when that comes about,’ he wrote, though it may have been that his expectation of Japan’s demise had to do not only with the anticipated Soviet intervention (assuming successful negotiations with China) but with the use of atomic bombs even sooner.50
As reports from Alamogordo continued to arrive in Potsdam, carried dutifully by Stimson to Truman, Byrnes, and Churchill, the President’s confidence rose, and so did his doubts about the need for Soviet involvement in the war. By the 18th, Truman seemed to Stimson ‘greatly reenforced’ in his determination to make the Soviets see reason. The next day, as he boasted to Bess, he managed a ‘tough meeting’ with the Russians when he ‘reared up... and told ’em where to get off and they got off’. Having received a final, detailed report on Trinity on the 21st, Truman turned even more bumptious, quarreling vigorously with Stalin on Germany and the political future of Eastern Europe. Churchill was surprised at Truman’s performance—until Stimson gave him a copy of the latest Trinity report the following day. ‘Now I know what happened to Truman yesterday,’ the Prime Minister said. ‘When he got to the meeting after having read this report he was a changed man. He told the Russians just where they got on and off and generally bossed the whole meeting.’ It was not just the President’s attitude that had changed. Prodded by Byrnes, he now made it clear that he was disinclined to bend to Soviet demands, ‘apparently’, Stimson wrote privately, because he was ‘relying greatly upon the information as to Si’. The bomb meant, perhaps, that the Soviets would get less than they wanted from China—control of Outer Mongolia and the railways in Manchuria and leaseholds on the cities of Dairen and Port Arthur—that they would prove yielding in their occupied zones of Eastern Europe and Germany, and that, assuming the bomb ended the war quickly, they would not, in Byrnes’s words, ‘get so much in on the kill’ and thereby have only a small role to play in the post-surrender occupation of Japan.51
While the British, then, were promptly and fully informed about the Trinity test, the Russians were not, and the question remained: what, if anything, should they be told? Stimson and others thought Stalin should hear something about the bomb from official sources. Jimmy Byrnes wanted to stonewall, to let the Russians find out when others did, after the bomb had been dropped. Truman decided on a sort of compromise, though one tipped toward Byrnes’s position. At 7.30 in the evening of 24 July, the eighth plenary session of the Potsdam conference took a recess. Instructing Bohlen, his Russian interpreter, to stay put, Truman walked across the room to Stalin, turned him away from the group, and told him, with a casualness that was clearly strained, that the United States had ‘a new weapon of unusual destructive force’. According to Truman, Stalin replied that ‘he was glad to hear it and hoped we would make “good use” of it against the Japanese’. Truman and other US officials thought Stalin’s reply indicated that he did not know what weapon the President was talking about—no more, that is, ‘than the man in the moon’, as Truman said later. They were wrong. Stalin had in June received information, gleaned from Klaus Fuchs at Los Alamos, that a bomb test was scheduled for later in the summer, and the intelligence was later refined. Following the plenary, Stalin called Lavrenti Beria, head of the secret police, to ask what Soviet intelligence knew about the shot. Beria said there had been no information that a test had taken place, whereupon Stalin flew into a rage and told Beria he had been misinformed. Back at his villa Stalin, cursing ‘in ripe language’ about American machinations, declared that he would not be manipulated and vowed to speed production of a bomb.52
Out of the Potsdam conference came the eponymous declaration that spelled out surrender terms to the Japanese. Stimson, along with Joseph Grew and Secretary of the Navy James Forrestal, had in June drafted a statement of terms that offered a slight but significant modification of unconditional surrender: that the Japanese might retain ‘a constitutional monarchy under the present dynasty’. The ‘Committee of Three’, as the men called themselves, hoped that such a promise might tip the balance in the Japanese Cabinet, allowing its ‘peace faction’ to lead an exit from the war because the emperor, who might now be enlisted in the quest for peace, would escape punishment, removal from office, or humiliation. On 18 July, just after the conference had begun, the Joint Chiefs of Staff offered their support for retaining the Emperor as the only figure on the scene who could persuade the soldiers loyal to him to lay down arms. But Byrnes disliked the new draft of terms. He may have feared that seeming to soften US conditions, however subtly, might encourage Japanese hardliners to continue the fight in the hopes of gaining further concessions. Equally likely, Byrnes’s focus, as ever, rested on domestic politics, and he worried that the loophole made by the modification would enrage an American public bent on bringing to its knees the nation that had perpetrated Pearl Harbor, the Bataan ‘Death March’, and scores of reported atrocities against American (and other) prisoners.
This was Truman’s concern too. It was his view that Franklin Roosevelt had committed the United States to the policy of unconditional surrender, just as FDR had assumed, in authorizing a program to build an atomic bomb, that the bomb should be dropped when it was ready. The new president was willing to offer the Japanese a hint of leniency in the Potsdam Declaration, or what he believed was a hint: the Japanese could establish a government ‘in accordance with the[ir] freely expressed will’, though only in the presence ofUS occupation forces and only after other conditions had been met—among them the elimination of ‘the authority and influence of those who have deceived and misled the people of Japan into embarking on world conquest’, and the administration of ‘stern justice’ to all ‘war criminals’, perhaps including the Emperor. When Byrnes removed the imperial retention clause from the draft declaration, Truman tacitly agreed with his secretary of state by accepting the change. The Potsdam Declaration, issued on 26 July by the United States, Great Britain, and China (the Soviets were not asked to sign), thus offered Tokyo no meaningful modification of terms, only the peace of the vanquished, and in harsh language. Japan’s choice was ‘unconditional surrender’ or ‘prompt and utter destruction’.53
So the die was cast. When the Japanese government did not immediately accept the Potsdam Declaration—Prime Minister Kantaro Suzuki reportedly said, on 28 July, that Japan would ‘ignore’ it (mokusatsu)—the Americans moved ahead with their plans to drop an atomic bomb on the first target city, Hiroshima. The uranium core of the bomb, encased in a cylinder oflead and weighing 300 pounds, had left San Francisco on the day of the Trinity shot and arrived at Tinian Island in the Marianas, seized from Japan the previous summer, on the 26th, the day the Potsdam Declaration was issued. Tinian was the home of the Air Force’s 509th Composite Group, members of which had been designated and trained to deliver the bomb. Colonel Paul Tibbets would command the B-29 that would carry Little Boy to its target. Delivery was set for 6 August, as long as the weather cooperated.