July 1945: the war in Europe was over; but in prospect still was the long agony of battle against Japan. The experience at Okinawa was regarded as an indication of the ordeal that would have to be endured.

Truman, Stalin and Churchill had agreed to meet in mid-July in the vicinity of Berlin. TERMINAL was selected as an appropriate code designation for their conference. For its purposes were to dispose of the unsettled issues left by the European War and make a start upon the tasks of peace. Provisional lists of the matters to be discussed, charts of the work ahead, had been circulated by the governments.

But the Americans left for Potsdam with an exciting secret--which they kept out of their memos as well as off their tongues. They knew that soon the first test was to be made of the atomic weapon which had been long in conception and construction.[i]

Secretary of War Stimson, who bore the focal responsibility for the quivering decisions that would have to be faced at once if the test went well, was planning to go to Potsdam. The President agreed that he should be close at hand when the results were known. Moreover, as Stimson told Secretary of State Byrnes, he wanted to learn for himself more about the task assigned to the Army in the American Zone in Germany and in the four-power administration.

His thoughts about S-1 (as the atomic weapon was identified), like those of the President, circled around its possible use in the war against Japan rather than its bearing on the matters that were to be discussed in the conference at Potsdam. Its first great impact was upon the issuance of a last warning to Japan--the Potsdam Declaration--and the ending of the struggle in the Pacific. However, before entering into the lanes along which the work of the conference flowed, we ought to summon the stirring reports that reached Potsdam about the test in New Mexico just as the conference was starting. Having done that we can yield to the temptation to speculate about the way in which these may have affected the outcome of the conference. In that connection we shall be obliged to note what was said to Stalin about the new weapon. As we tell of these events, we may find ourselves straggling from known facts--those conveyed by the reports from the scene of the explosion and in the minutes of the conference--to impressions and surmises.


The formal opening of the conference was put off from the 16th to the 17th of July because Stalin had suffered a slight heart attack. Truman used the liberated day to drive into Berlin from his quarters at Babelsburg. "In that two-hour drive," he later wrote, "I saw evidence of a great world tragedy. . . ." Upon his return Stimson hurried over to tell him and Byrnes of a message just in from George Harrison, who was acting as Chairman of the Interim Committee on S-1 while Stimson was away.[ii] This was the first flash about the detonation of the bomb in Alamogordo. In code expression it read: "Operated on this morning. Diagnosis not yet complete but results seem satisfactory and already exceed expectations. Local press release necessary as interest extends great distance.[iii] Doctor [General] Groves pleased. He returns [to Washington] tomorrow. I will keep you posted."[iv]

Harrison did so in another short message that got to Stimson the next day or evening (the 17th). This read: "Doctor Groves has just returned most enthusiastic and confident that the little boy is as husky as his big brother. The light in his eyes discernible from here [Washington] to Highhold [Stimson's house on Long Island, 250 miles away] and I could have heard his screams from here to my farm [at Upperville, Virginia, 40 miles away]."[v]

Stimson at once discussed the latest news with Byrnes and passed it on to Churchill. The Secretary of War noted in his Diary that the Prime Minister had not heard of the great events from British officials in Washington, that he was much cheered up, and strongly against disclosing information about the weapon to the Russians. On the next day, the 18th, Stimson talked over with the President the import of Harrison's second message. In his Diary entry for that day he noted that the President seemed to him "highly delighted . . . [and] very greatly reinforced over the message from Harrison, and said he was very glad I had come to the meeting."[vi]

On the 21st, just before noon, a courier put in Stimson's hands the special report which General Groves had prepared. He found it was ". . . an immensely powerful document, clearly and well written, and with supporting documents of the highest importance," and that "it gave a pretty full and eloquent report of the tremendous success of the test and revealed far greater destructive power than we expected in S-1."

Longish as is this report from the scene of the explosion, in order to appreciate its impress it should be read in full as it was by the recipients at Potsdam.


Subject: The Test

1. This is not a concise, formal military report but an attempt to recite what I would have told you if you had been here on my return from New Mexico.

2. At 0530, 16 July 1945, in a remote section of the Alamogordo Air Base, New Mexico, the first full-scale test was made of the implosion type atomic fission bomb. For the first time in history there was a nuclear explosion. And what an explosion! . . . The bomb was not dropped from an airplane but was exploded on a platform on top of a 100-foot high steel tower.

3. The test was successful beyond the most optimistic expectations of anyone. Based on the data which it has been possible to work up to date, I estimate the energy generated to be in excess of the equivalent of 15,000 to 20,000 tons of T.N.T.; and this is a conservative estimate. Data based on measurements which we have not yet been able to reconcile would make the energy release several times the conservative figure. There were tremendous blast effects. For a brief period there was a lighting effect within a radius of 20 miles equal to several suns in midday; a huge ball of fire was formed which lasted for several seconds. This ball mushroomed and rose to a height of over 10,000 feet before it dimmed. The light from the explosion was seen clearly at Albuquerque, Santa Fe, Silver City, El Paso and other points generally to about 180 miles away. The sound was heard to the same distance in a few instances but generally to about 100 miles. Only a few windows were broken although one was some 125 miles away. A massive cloud was formed which surged and billowed upward with tremendous power, reaching the substratosphere at an elevation of 41,000 feet, 36,000 feet above the ground, in about 5 minutes, breaking without interruption through a temperature inversion at 17,000 feet which most of the scientists thought would stop it. Two supplementary explosions occurred in the cloud shortly after the main explosion. The cloud contained several thousand tons of dust picked up from the ground and a considerable amount of iron in the gaseous form. Our present thought is that this iron ignited when it mixed with the oxygen in the air to cause these supplementary explosions. Huge concentrations of highly radioactive materials resulted from the fission and were contained in this cloud.

4. A crater from which all vegetation had vanished, with a diameter of 1,200 feet and a slight slope toward the center, was formed. In the center was a shallow bowl 130 feet in diameter and 6 feet in depth. The material within the crater was deeply pulverized dirt. The material within the outer circle is greenish and can be distinctly seen from as much as 5 miles away. The steel from the tower was evaporated. 1,500 feet away there was a 4-inch iron pipe 16 feet high set in concrete and strongly guyed. It disappeared completely.

5. One-half mile from the explosion there was a massive steel test cylinder weighing 220 tons. The base of the cylinder was solidly encased in concrete. Surrounding the cylinder was a strong steel tower 70 feet high, firmly anchored to concrete foundations. This tower is comparable to a steel building bay that would be found in a typical 15 or 20-story skyscraper or in warehouse construction. Forty tons of steel were used to fabricate the tower which was 70 feet high, the height of a six-story building. The cross bracing was much stronger than that normally used in ordinary steel construction. The absence of the solid walls of a building gave the blast a much less effective surface to push against. The blast tore the tower from its foundations, twisted it, ripped it apart and left it flat on the ground. The effects on the tower indicate that, at that distance, unshielded permanent steel and masonry buildings would have been destroyed . . . I no longer consider the Pentagon a safe shelter from such a bomb. Enclosed are a sketch showing the tower before the explosion and a telephotograph showing what it looked like afterwards. None of us had expected it to be damaged.

6. The cloud traveled to a great height first in the form of a ball, then mushroomed, then changed into a long trailing chimney-shaped column and finally was sent in several directions by the variable winds at the different elevations. It deposited its dust and radioactive materials over a wide area. It was followed and monitored by medical doctors and scientists with instruments to check its radioactive effects. While here and there the activity on the ground was fairly high, at no place did it reach a concentration which required evacuation of the population. Radioactive material in small quantities was located as much as 120 miles away. The measurements are being continued in order to have adequate data with which to protect the Government's interests in case of future claims. For a few hours I was none too comfortable about the situation.

7. For instance, as much as 200 miles away, observers were stationed to check on blast effects, property damage, radioactivity and reactions of the population. While complete reports have not yet been received, I know that no persons were injured nor was there any real property damage outside our Government area. As soon as all the voluminous data can be checked and correlated, full technical studies will be possible.

8. Our long range weather predictions had indicated that we could expect weather favorable for our tests beginning on the morning of the 17th and continuing for 4 days. This was almost a certainty if we were to believe our long range forecasters. The prediction for the morning of the 16th was not so certain but there was about an 80 percent chance of the conditions being suitable. During the night there were thunderstorms with lightning flashes all over the area. The test had been originally set for 0400 hours and all the night through, because of the bad weather, there were urgings from many of the scientists to postpone the test. Such a delay might well have had crippling results due to mechanical difficulties in our complicated test setup. Fortunately, we disregarded the urgings. We held firm and waited the night through hoping for suitable weather. We had to delay an hour and a half, to 0530, before we could fire. This was 30 minutes before sunrise.

9. Because of bad weather, our two B-29 observation airplanes were unable to take off as scheduled from Kirkland Field at Albuquerque and when they finally did get off, they found it impossible to get over the target because of the heavy clouds and the thunderstorms. Certain desired observations could not be made and while the people in the airplanes saw the explosion from a distance, they were not as close as they will be in action. We still have no reason to anticipate the loss of our plane in an actual operation although we cannot guarantee safety.

10. Just before 1100 the news stories from all over the state started to flow into the Albuquerque Associated Press. I then directed the issuance by the Commanding Officer, Alamogordo Air Base, of a news release as shown on the inclosure. With the assistance of the Office of Censorship we were able to limit the news stories to the approved release supplemented in the local papers by brief stories from the many eyewitnesses not connected with our project. One of these was a blind woman who saw the light.

11. Brigadier General Thomas F. Farrell was at the control shelter located 10,000 yards south of the point of explosion. His impressions are given below: Impressions of Brigadier General Thomas F. Farrell at control shelter 10,000 yards south of point of explosion:

"The scene inside the shelter was dramatic beyond words. In and around the shelter were some 20-odd people concerned with last minute arrangements prior to firing the shot. Included were: Dr. Oppenheimer, the Director who had borne the great scientific burden of developing the weapon from the raw materials made in Tennessee and Washington and a dozen of his key assistants--Dr. Kistiakowsky, who had developed the highly special explosives; Dr. Bainbridge, who supervised all the detailed arrangements for the test; Dr. Hubbard, the weather expert, and several others. Besides these, there were a handful of soldiers, two or three Army officers and one Naval officer. The shelter was cluttered with a great variety of instruments and radios.

"For some hectic two hours preceding the blast, General Groves stayed with the Director, walking with him and steadying his tense excitement. Every time the Director would be about to explode because of some untoward happening, General Groves would take him off and walk with him in the rain, counselling with him and reassuring him that everything would be all right. At twenty minutes before zero hour, General Groves left for his station at the Base Camp [some nine miles from the point of explosion], first because it provided a better observation point and second, because of our rule that he and I must not be together in situations where there is an element of danger, which existed at both points.

"Just after General Groves left, announcements began to be broadcast of the interval remaining before the blast. They were sent by radio to the other groups participating in and observing the test. As the time interval grew smaller and changed from minutes to seconds, the tension increased by leaps and bounds. Everyone in that room knew the awful potentialities of the thing that they thought was about to happen. The scientists felt that their figuring must be right and that the bomb had to go off but there was in everyone's mind a strong measure of doubt.[vii] The feeling of many could be expressed by 'Lord, I believe; help Thou mine unbelief.' We were reaching into the unknown and we did not know what might come of it. It can be safely said that most of those present--Christian, Jew and atheist--were praying and praying harder than they had ever prayed before. If the shot were successful, it was a justification of the several years of intensive effort of tens of thousands of people--statesmen, scientists, engineers, manufacturers, soldiers and many others in every walk of life.

"In that brief instant in the remote New Mexico desert the tremendous effort of the brains and brawn of all the people came suddenly and startlingly to the fullest fruition. Dr. Oppenheimer, on whom had rested a very heavy burden, grew tenser as the last seconds ticked off. He scarcely breathed. He held on to a post to steady himself. For the last few seconds, he stared directly ahead and then when the announcer shouted 'Now!' and there came this tremendous burst of light followed shortly thereafter by the deep growling roar of the explosion, his face relaxed into an expression of tremendous relief. Several of the observers standing back of the shelter to watch the lighting effects were knocked flat by the blast.

"The tension in the room let up and all started congratulating each other. Everyone sensed 'This is it!' No matter what might happen now all knew that the impossible scientific job had been done. Atomic fission would no longer be hidden in the cloisters of the theoretical physicists' dreams. It was almost full grown at birth. It was a great new force to be used for good or for evil. There was a feeling in that shelter that those concerned with its nativity should dedicate their lives to the mission that it would always be used for good and never for evil.

"Dr. Kistiakowsky, the impulsive Russian, (Interpolation by Groves at this point, 'an American and Harvard professor for many years') threw his arms around Dr. Oppenheimer and embraced him with shouts of glee. Others were equally enthusiastic. All the pent-up emotions were released in those few minutes and all seemed to sense immediately that the explosion had far exceeded the most optimistic expectations and wildest hopes of the scientists. All seemed to feel that they had been present at the birth of a new age--The Age of Atomic Energy--and felt their profound responsibility to help in guiding into right channels the tremendous forces which had been unlocked for the first time in history.

"As to the present war, there was a feeling that no matter what else might happen, we now had the means to insure its speedy conclusion and save thousands of American lives. As to the future, there had been brought into being something big and something new that would prove to be immeasurably more important than the discovery of electricity or any of the other great discoveries which have so affected our existence.

"The effects could well be called unprecedented, magnificent, beautiful, stupendous and terrifying. No man-made phenomenon of such tremendous power had ever occurred before. The lighting effects beggared description. The whole country was lighted by a searing light with the intensity many times that of the midday sun. It was golden, purple, violet, gray and blue. It lighted every peak, crevasse and ridge of the nearby mountain range with a clarity and beauty that cannot be described but must be seen to be imagined. It was that beauty the great poets dream about but describe most poorly and inadequately. Thirty seconds after the explosion came first the air blast pressing hard against the people and things, to be followed almost immediately by the strong, sustained, awesome roar which warned of doomsday and made us feel that we puny things were blasphemous to dare tamper with the forces heretofore reserved to The Almighty. Words are inadequate tools for the job of acquainting those not present with the physical, mental and psychological effects. It had to be witnessed to be realized." (End of General Farrell's account.)

12. My [General Groves] impressions of the night's high points follow:

After about an hour's sleep I got up at 0100 and from that time on until about five I was with Dr. Oppenheimer constantly. Naturally he was very nervous, although his mind was working at its usual extraordinary efficiency. I devoted my entire attention to shielding him from the excited and generally faulty advice of his assistants who were more than disturbed by their excitement and the uncertain weather conditions. By 0330 we decided that we could probably fire at 0530. By 0400 the rain had stopped but the sky was heavily overcast. Our decision became firmer as time went on. During most of these hours the two of us journeyed from the control house out into the darkness to look at the stars and to assure each other that the one or two visible stars were becoming brighter. At 0510 I left Dr. Oppenheimer and returned to the main observation point which was 17,000 yards from the point of explosion. In accordance with our orders I found all personnel not otherwise occupied massed on a bit of high ground.

At about two minutes of the scheduled firing time all persons lay face down with their feet pointing towards the explosion. As the remaining time was called from the loud speaker from the 10,000 yard control station there was complete silence. Dr. Conant said he had never imagined seconds could be so long. Most of the individuals in accordance with orders shielded their eyes in one way or another. There was then this burst of light of a brilliance beyond any comparison. We all rolled over and looked through dark glasses at the ball of fire. About forty seconds later came the shock wave followed by the sound, neither of which seemed startling after our complete astonishment at the extraordinary lighting intensity. Dr. Conant reached over and we shook hands in mutual congratulations. Dr. Bush, who was on the other side of me, did likewise. The feeling of the entire assembly was similar to that described by General Farrell, with even the uninitiated feeling profound awe. Drs. Conant and Bush and myself were struck by an even stronger feeling that the faith of those who had been responsible for the initiation and the carrying on of this Herculean project had been justified. I personally thought of Blondin crossing Niagara Falls on his tightrope, only to me this tightrope had lasted for almost three years, and of my repeated confident-appearing assurances that such a thing was possible and that we would do it.

13. A large group of observers were stationed at a point about 27 miles north of the point of explosion. Attached is a memorandum written shortly after the explosion by Dr. E. O. Lawrence which may be of interest.

14. While General Farrell was waiting about midnight for a commercial airplane to Washington at Albuquerque--120 miles away from the site--he overheard several airport employees discussing their reactions to the blast. One said that he was out on the parking apron; it was quite dark; then the whole southern sky was lighted as though by a bright sun; the light lasted several seconds. Another remarked that if a few exploding bombs could have such an effect, it must be terrible to have them drop on a city.

15. My liaison officer at the Alamogordo Air Base, sixty miles away, made the following report:

"There was a blinding flash of light that lighted the entire northwestern sky. In the center of the flash, there appeared to be a huge billow of smoke. The original flash died down, there arose in the approximate center of where the original flash had occurred an enormous ball of what appeared to be fire and closely resembled a rising sun that was 3/4 above a mountain. The ball of fire lasted approximately fifteen seconds, then died down and the sky resumed an almost normal appearance.

"Almost immediately, a third, but much smaller, flash and billow of smoke of a whitish-orange color appeared in the sky, again lighting the sky for approximately 4 seconds. At the time of the original flash, the field was lighted well enough so that a newspaper could easily have been read. The second and third flashes were of much lesser intensity.

"We were in a glass-enclosed control tower some 70 feet above the ground and felt no concussion or air compression. There was no noticeable earth tremor although reports overheard at the Field during the following 24 hours indicated that some believed that they had both heard the explosion and felt some earth tremor."

16. I have not written a separate report for General Marshall as I feel you will want to show this to him. I have informed the necessary people here of our results. Lord Halifax after discussion with Mr. Harrison and myself stated that he was not sending a full report to his government at this time. I informed him that I was sending this to you and that you might wish to show it to the proper British representatives.

17. We are all fully conscious that our real goal is still before us. The battle test is what counts in the war with Japan.

18. May I express my deep personal appreciation for your congratulatory cable to us and for the support and confidence which I have received from you ever since I have had this work under my charge.

19. I know that Colonel Kyle will guard these papers with his customary extraordinary care.

L. R. GROVES[viii]

Stimson at once sought an engagement with the President. It was fixed for half-past three that afternoon. In the interval Stimson told Marshall of the main features of Groves' report. When he got to the "Little White House," he asked the President to call Byrnes in, and read the message in full to them. The President was, in the words of Stimson's Diary, "tremendously pepped up by it . . . and said that it gave him an entirely new feeling of confidence." Why the report was such an elixir will be clear to all those who have knowledge of the tussles that were going on around the conference table.

Stimson then hurried over to Churchill's quarters and gave him the typed memo from Groves. The Prime Minister could not read it through before he had to leave for the Fifth Plenary Session with Truman and Stalin. He asked Stimson to come again the following morning, when he would be free.

Before going over to see the Prime Minister that next forenoon (the 22nd) Stimson stopped by the "Little White House" to pick up a paper which he had left with the President the day before, summarizing his ideas about sharing knowledge of the new weapon with the Russians, and the possibility of bringing the new force--atomic energy--under effective international control. As he was leaving he told Truman that Harrison had just assured him that a bomb would be ready for use against Japan early in August.

Then on to the residence of the Prime Minister he went, and stood by while the message from Groves was being read in full. On putting it down, Churchill, all animation, leaned forward in his chair, waved his cigar and said, "Stimson, what was gunpowder? Trivial. What was electricity? Meaningless. This atomic bomb is the second coming in wrath."[ix]


The consequent questions of whether, when, how and how much to tell the Russians about the new weapon had perplexed the informed American officials ever since the scientists and engineers had forecast its being.

In 1943 at Hyde Park, Roosevelt and Churchill had entered into an agreement which stated that "(1) The suggestion that the world should be informed regarding its [S-1] control and use is not accepted. The matter should continue to be regarded as of the utmost secrecy; but when a 'bomb' is finally available, it might perhaps, after mature consideration, be used against the Japanese who should be warned that the bombardment will be repeated until they surrender."[x]

The Interim Committee, without knowing of this accord, had early in June agreed that the American Government ought not to reveal the existence of the weapon to Russia or anyone else until after it was proven in use against Japan. When reporting to the President on June 6 about the points of agreement reached in the Interim Committee, Stimson had stressed this conclusion. He had then said he was perplexed as to what might happen when the President met with Stalin and Churchill. Truman had remarked that the postponement of the conference until the middle of July would give the wanted time. The Secretary of War had not been wholly reassured. What if the tests were delayed?

Stimson had then summed up for the President the discussions that had been going on in and out of the Interim Committee on future control of this new terrific force. The only suggestion, he said, which the Committee had advanced was that countries should promise to make public all the work they were doing in this field, and to form an international control group with full powers of inspection in all countries. Presciently, he remarked that he realized that this plan was imperfect and the Russians might not agree with it. If they did not, all we could do, he thought, was to accumulate enough fissionable material as insurance. In any case, he had reiterated his conviction that no disclosure ought to be made to anyone until an agreement on control was working effectively. Marshall had been of the same determined opinion.

Could the United States, the President wondered, get something of value in return for sharing information about atomic fission with the Soviet Union? Might we be able to get greater coöperation in arriving at accords in regard to Poland, Rumania, Jugoslavia, Manchuria, for example?

The Combined (U.S.-British) Policy Committee on July 4, two days before the American group left for Potsdam, had pondered over the same problem of what, if anything, to tell the Russians. The British and Canadian members (Field Marshal Sir Henry Maitland Wilson, liaison for the British Chiefs of Staff, and the Honorable C. D. Howe, Canadian Minister of Munitions) had gone along with Stimson's ideas of what had best be done. As recorded in the minutes of this discussion:

The Chairman said he was thinking of an earlier period, viz. the forthcoming meeting with Stalin. His own opinion had been very much influenced by the probable use within a few weeks after the meeting. If nothing was said at this meeting about the T.A. weapon, its subsequent early use might have a serious effect on the relations of frankness between the three great Allies. He had therefore advised the President to watch the atmosphere at the meeting. If mutual frankness on other questions was found to be real and satisfactory, then the President might say that work was being done on the development of atomic fission for war purposes; that good progress had been made; and that an attempt to use a weapon would be made shortly, though it was not certain that it would succeed. If it did succeed, it would be necessary for a discussion to be held on the best method of handling the development in the interests of world peace and not for destruction. If Stalin pressed for immediate disclosure the President might say that he was not prepared to take the matter further at the present time. . . .[xi]

All these questions had been left hanging in the air. There they had stayed until the President got to Potsdam and the news of the results of the test in New Mexico overtook him and Stimson and Byrnes. When they learned that it would soon be available for use against Japan, they had to make up their minds. The quest for the correct course led them into even more intense talk about how much to tell the Russians.


All recognized that it would be sensible as well as proper to let Stalin know of the achievement. For of course he would learn of it as soon as the bomb was used against the Japanese--which would be in about a fortnight. But how much should he be told of its nature? Above all else, should we share the knowledge as to how the new weapon was made? On that question, as has been told, the ruling official opinion had been steady from the start: we must not do so until or unless an agreement should be reached for international inspection and control. The only notable challenge to this conclusion was that which had been offered by some of the scientists who were convinced that the Soviet Union could easily and quickly learn how to make the new weapon whether or not we told them what we knew. If that were true, they had argued that by sharing our knowledge we would be showing trust, and so win trust; while if we concealed what we knew, we would, by showing mistrust, stimulate their hostility, suspicion and rivalry.

Stimson meditated over this dilemma, fretted over it during sleepless hours of the night. For he had taught himself to live by the maxim that the way to win trust was to give it; and this clashed with the dark lessons of history about the ways of absolute dictatorship. The President took the view that it was common sense to wait until we were sure. Byrnes thought unguarded openness would bring advantage only to the Russians.

But at Potsdam these longer and more lasting aspects of the question were thrust into the background by thoughts of more immediate consequences. What would be the effect of opening the doors to knowledge about the weapon or of keeping them closed on the Soviet attitude in the disputatious talks on European questions that were going on? How might the Soviet decision whether or not to enter the Pacific War be affected? Or the timing of its entry? Or its attitude toward the situation in China?

When on July 18 Truman talked with Churchill about the new weapon they reviewed these quandaries. Truman's attitude and Churchill's response are recorded in a note the Prime Minister made for the War Cabinet:

The President showed me telegrams about the recent experiment, and asked what I thought should be done about telling the Russians. He seemed determined to do this, but asked about the timing, and said he thought that the end of the Conference would be best. I replied that if he were resolved to tell it might well be better to hang it on the experiment, which was a new fact on which he and we had only just had knowledge. Therefore he would have a good answer to any question, "Why did you not tell us this before?" He seemed impressed with this idea, and will consider it.

On behalf of His Majesty's Government, I did not resist his proposed disclosure of the simple fact that we have this weapon. He reiterated his resolve at all costs to refuse to divulge any particulars. . . .[xii]

On thinking the matter over longer, Churchill developed a positive disposition to let the Russians know we had the new weapon. After Stimson talked with him again on the 22nd, the Secretary of War entered in his Diary, "He [Churchill] now not only was not worried about giving the Russians information on the matter, but was rather inclined to use it as an argument in our favor in the negotiations. The sentiment of the four of us [Stimson, Bundy, Churchill, Cherwell] was unanimous in thinking that it was advisable to tell the Russians at least that we were working on the subject and intended to use it if and when it was successfully finished."[xiii]

But Stimson's impulse to be more trustful and revealing was still checked by his ominous view of the system of dictatorship under which the Russians lived. His worry and sense of being on the side lines had found outlet in a memo which he had given to the President the day before. In this he had expressed the opinion that the basic difficulty in our relations with Russia was that there was no personal or political freedom in that country, that it was ruled by an arbitrary autocracy and that there could not be close and reliable relations between such a system and ours. Thus he had urged that we should try to get Stalin to take the lead in introducing freedoms into the Soviet Union; otherwise he feared that a new war was inevitable and that it would bring about the destruction of our civilization. The memo concluded:

The foregoing has a vital bearing upon the control of the vast and revolutionary discovery of "X" [atomic energy] which is now confronting us. Upon the successful control of that energy depends the future successful development or destruction of the modern civilized world. The Committee appointed by the War Department [the Interim Committee] which has been considering that control has pointed this out in no uncertain terms and has called for an international organization for that purpose. After careful reflection I am of the belief that no world organization containing as one of its dominant members a nation whose people are not possessed of free speech but whose governmental action is controlled by the autocratic machinery of a secret political police, cannot [can] give effective control of this new agency with its devastating possibilities.

I therefore believe that before we share our new discovery with Russia we should consider carefully whether we can do so safely under any system of control until Russia puts into effective action the proposed constitution which I have mentioned. If this is a necessary condition, we must go slowly in any disclosures or agreeing to any Russian participation whatsoever and constantly explore the question how our headstart in "X" and the Russian desire to participate can be used to bring us nearer to the removal of the basic difficulties which I have emphasized.[xiv]

In other words, even if our headstart was only temporary, could it not be used to influence the Soviet Union to make life safer for the world by converting itself into a constitutional democracy, in which citizens were free and rulers under restraint? How grand the purpose, how far away the chance! But to Stimson, as Elting Morison in his forthcoming biography of the Secretary of War has observed, "That these difficulties could, with care and time, be removed was not 'an idle dream.' "[xv]

On the morning of the 24th Stimson showed Truman the most recent message from Harrison giving the probable date when all would be in order to use the bomb against Japan. That was being assembled in Tinian. The President was delighted and said that it gave him his cue for the issuance of the final warning to Japan to accept the terms we and the British were offering, as the only way to escape utter destruction. He wanted to issue this summons to surrender as soon as Chiang Kai-shek, who had been asked to approve the text, answered. At lunch, Truman talked over with Byrnes how Stalin might be told enough to invalidate any future reproach that information of military importance had been kept from him, but no more. They had agreed that it should be done in a rather offhand way.

That afternoon the Combined Chiefs of Staff had what was deemed a rewarding session with their Soviet associates. The Plenary Session of the Heads of State was, however, rather unproductive and at moments discordant. Still Stalin had shown some disposition to heed Western wishes. The conferees rose from their places with amiable nods after approving the worksheet for their next meeting. As they were standing around in small groups waiting for their cars to come, the President, along with Bohlen, sauntered over to Stalin. His own later account of their very brief chat is as casual as his act was made to appear. It might even be called "humdrum."

On July 24 I casually mentioned to Stalin that we had a new weapon of unusual destructive force. The Russian Premier showed no special interest. All he said was that he was glad to hear it and hoped we would make "good use of it against the Japanese."[xvi]

Both Churchill and Byrnes were observing the two intently. Churchill stood perhaps five yards away and watched with the closest attention to measure the effect of what the President was going to tell Stalin. His impression was the same though more enlivened by his dramatic imagination.

... I can see it all as if it were yesterday. He seemed to be delighted. A new bomb! Of extraordinary power! Probably decisive on the whole Japanese war! What a bit of luck! This was my impression at the moment, and I was sure that he had no idea of the significance of what he was being told. . . .[xvii]

When he asked Truman how the talk had gone the President told him how Stalin had been pleased but not inquisitive. And when Byrnes asked him the same question the President answered that all Stalin had said was "that he was glad to hear of the bomb and he hoped we would use it."[xviii]

What had been feared had not come to pass. Stalin had not tried to find out what the nature of the new weapon was nor how it was made. He had not suggested that Soviet officers or technicians be allowed to examine or witness its use. But was this only because he did not realize the significance of what Truman was telling him? He was not dull in grasping the meaning of even the most passing remark, or incurious about any improvement in weapons. It did not occur to any of the American and British officials who were at Potsdam that Stalin might already have knowledge of the production and testing of the new weapon. Possibly, probably, he did not. But that is curious in the light of what has since been learned of the inside accounts of what was being done at Los Alamos that had been transmitted to the Soviet Government by its agents in New Mexico and elsewhere.

In any case, Truman's statement did not seem to either the American or British observers to have influenced the Russian attitude toward the situations that were being talked about at the conference. Nor can the historian going over the record of the conference discern signs that it did so. But this steadiness may have been dissimulation. Stalin was quite able to conceal any glimmer of the idea that the diplomatic or military balance between the West and the Soviet Union might be affected by the new weapon. Or it might have been due to his certainty that the American Government would not use it against the Soviet Union because of any current difference. Or it may have been that his technical advisers were already telling him that they could in due course repeat the production. These are some of the conjecturable, maybe imaginary, reasons for Stalin's response, for the way in which he matched Truman's casualness. But whether it was due to failure to grasp the significance of Truman's statement, or dissimulation, this student for one would be surprised if there are not in the Soviet archives orders which, if not issued long before July 24, were dispatched that night from Potsdam, urging the Soviet intelligence network to do its utmost to find out all it could about the new weapon, and asking the scientific sections of the military to report their surmises about its nature and methods of manufacture.


After his first quick and interrupted scanning of Groves' long and vivid report on the New Mexico bomb test which has been quoted, Churchill had said to Stimson that he had noticed during the session of the conference the afternoon before (the 21st) that the President was evidently much fortified by some news or event. He had seemed to this alert observer to be a changed person, in the way in which he had maintained his stand against the Russians in a most emphatic and decisive manner. And so, Churchill added, he too was a different man.

Some of the President's attendant staff had the same impression of new gusto and greater firmness. But alas, it is not detectable in the dull monochrome tone of the American minutes of the conference. Nor can I discern that the change in mood or attitude or judgment lasted through the following days of the conference. Certainty that we would be able to defeat the Soviet Union in war did not cause Truman or his advisers, military or civilian, to be more demanding. It apparently did not lead them to anticipate that, after the proof in use against Japan of the great destructive power of the weapon, the Russians would be more yielding.

Nor was our wish to have Russian coöperation in the war against Japan dispelled. When, after the receipt of the Groves report, Stimson told Marshall that the President would like to know whether he [Marshall] still thought we needed the Russians in the Pacific War or whether we could get on without them, the answer was neither direct nor conclusive. Marshall said that the fact that the Russians were amassing large forces on the Manchurian frontier was already serving one of the purposes for which we wished them to come into the war--to cause the Japanese to keep their army in Manchuria. He also pointed out that even if we defeated the Japanese without or before Russian entry they could, if they so wished, march into Manchuria anyhow and take what they wanted. In sum Marshall gave Stimson the impression that since we had the atomic bomb, Russian aid was no longer really needed to conquer Japan or much wanted; but that it would bring the end quicker and with smaller loss of life; and since in any event the Soviet forces could secure control of Manchuria [and possibly Korea and the Kuriles] it was still expedient to solicit its entry.

The plans for coördinated operations of American and Soviet forces in the Pacific, which were during the next few days (July 24-26) agreed on by the American and Soviet Chiefs of Staff, sealed their joint intention tightly. Truman and Stalin liked the prospect and approved the accord. Churchill, whatever his qualms might have been, made no objection. He had already (on the 24th) concurred in the Final Report of the Combined (U.S.-British) Chiefs of Staff which included in the sections stating the basic understandings and policies for the prosecution of the war against Japan the provision: "Encourage Russian entry into the war against Japan. Provide such aid to her war-making capacity as may be necessary and practicable in connection therewith."

To sum up: the secret knowledge of the bomb did cause the Americans and British to be firm in their resistance to Soviet wishes that they thought excessive or perilous. It was a buttress for the policy of fairness and friendliness to which they were clinging. As succinctly expressed by Churchill in "Triumph and Tragedy," ". . . we should not need the Russians. . . . We had no need to ask favors of them." But either the Americans at Potsdam did not know how to use their command of the new weapon effectively as a threat, or chose not to use it in that way. Was not the American Government resting the whole structure of its policy on the conviction that situations and disputes were to be settled only by peaceful means and orderly procedures? The intention was to find ways to use the technical triumph in New Mexico for the service of the ideal principles which had been endorsed at San Francisco. Even if Russia could be frightened or coerced by the bomb to give in against its will on matters before the conference, would the West be well served if in consequence it turned against the United Nations? Such, in so far as I can gather the thoughts of those who guided American diplomatic and military decisions at Potsdam, was the trend of their sober reflections.

Thus the light of explosion "brighter than a thousand suns" filtered into the conference rooms at Potsdam only as a distant gleam. It was the fire, however, concealed in the final call for Japanese surrender that was issued from Potsdam. And its full glare was to become burningly visible over Hiroshima not many days later.

[i] The material in this article is drawn from a forthcoming book by the author.

[ii] In writing later about the first report given him by Stimson of the results of the test, Truman seems to have been confused in his memory of detail. As recounted in "Memoirs," v. 1, "Year of Decisions" (New York: Doubleday, 1955), p. 415, "The historic message of the first explosion of an atomic bomb was flashed to me in a message from Secretary of War Stimson on the morning of July 16 . . . . Stimson flew to Potsdam the next day to see me and brought with him the full details of the test." But Stimson was in Babelsburg on the 16th and took the first message in person to Truman that same evening. The "full details" of the test, brought by special courier, were not received until a few days later.

[iii] The flash and noise of the explosion seen and heard far away aroused excited curiosity. The Commanding Officer of the Alamogordo Army Air Base, General Ericson, gave the press a statement which said that the explosion had occurred in a remotely located ammunition magazine. The explanation seems to have been accepted calmly and without question. No mention either of the explosion or its cause is to be found in the issues of The New York Times or Herald Tribune of July 17, probably as a result of voluntary censorship.

[iv] Potsdam Papers. Document No. 1311. Editor's Note: The Potsdam Papers, including the long memorandum beginning on the next page, have not yet been published, but will probably be brought out by the Department of State during the coming year.

[v] Potsdam Papers. Document No. 1312.

[vi] Here this historian runs into another instance of conflicting records of chronology which is left for other researchers to clear up. Stimson's Diary does not mention any general convocation of military and civilian heads to confer about the news either on the 17th or 18th. But Truman (op. cit., p. 415) wrote that on the 17th Stimson brought with him "full details of the test" and that he called in at once Byrnes, Leahy, Marshall, Arnold and King to review our military strategy in the light of this revolutionary development. The Joint Chiefs did meet on the morning of the 17th, but not with the President.

In "Triumph and Tragedy" (Boston: Houghton Mifflin, 1953), p. 638-639, Churchill wrote that on the morning of the 18th ". . . a plane arrived with a full description of this tremendous event in the human story," and that the President invited him to confer "forthwith," Marshall and Leahy being present. But the report containing the "full description" was not put in Stimson's hands by courier until the 21st. However, that Churchill did have some sort of talk with Truman on the 18th is verified by the note bearing that date which he wrote for the War Cabinet, ibid., p. 640-641.

[vii] The components of the detonating mechanisms had been tested and proven. But the anticipated occurrence of the explosion was based on theoretical reckoning which had not yet been experimentally validated. So doubt remained as to whether some important element had not been overlooked or wrongly calculated.

[viii] Potsdam Papers. Document No. 1313.

[ix] "Remembered Words," by Harvey H. Bundy, who was present at this talk with Churchill, in The Atlantic Monthly, March 1957.

[x] Potsdam Papers. Document No. 1314.

[xi] Potsdam Papers. Document No. 619. The members of the Committee were Stimson, Wilson, Howe and Dr. Vannevar Bush. On this occasion there were also present the British Ambassador (the Earl of Halifax), Sir James Chadwick, General Groves and George Harrison, as well as the Joint Secretaries, Harvey H. Bundy and Roger Makins.

[xii] Churchill, op. cit., p. 640-641.

[xiii] Stimson-Churchill conversation, Potsdam Papers. Minutes, July 22, 1945.

[xiv] Potsdam Papers. Document No. 1165.

[xv] Morison manuscript.

[xvi] Truman, op. cit., p. 416. As Truman later wrote to Professor Cate, one of the editors of the history of the Army Air Forces, "Premier Stalin smiled and thanked me for reporting the explosion to him, but I'm sure he did not understand its significance." Wesley F. Craven and James L. Cate., eds., "The Army Air Forces in World War II." Chicago: University of Chicago Press, 1953, v. 5, p. 712.

[xvii] Churchill, op. cit., p. 670.

[xviii] Byrnes, "Speaking Frankly." New York: Harper, 1947, p. 263.

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  • HERBERT FEIS, former Economic Adviser in the Department of State; author of "The Road to Pearl Harbor," "The China Tangle," "Churchill-Roosevelt-Stalin" and other works
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