The Trinity test on 16 July 1945 demonstrated that the United States had developed an atomic explosive. It did not establish that using one against a city was necessary, justified or certain to end the war. Those were different questions. Political and military officials were already considering use before the test, while scientists disagreed about a demonstration, prior warning and the consequences for future international security. [6] [10]
There was no single view shared by everyone who helped develop the weapon. The Franck Report argued for an international demonstration before combat use. A scientific advisory panel supported military use. Leo Szilard and fellow scientists petitioned for Japan to receive clearly stated surrender terms and an opportunity to accept them first. Their petition did not reach President Truman before Hiroshima. On 25 July, a military directive authorised the first atomic attack and further attacks as additional bombs became available. [1] [6] [13] [14] [16]
Part 12 established Japan’s military and diplomatic position before the atomic bombings. Part 13 follows the American decisions developing alongside it, chiefly from April through July 1945. We separate what people knew, what they recommended, what they hoped would happen and what they authorised. The chapter ends before the attacks. Their human consequences and their relationship to Soviet entry and Japan’s surrender belong to the next chapter, not to an outcome assumed in advance.
Previous chapter: Part 12 — 1945: Japan Before the Atomic Bombs. Next chapter: Part 14 — August 1945: Hiroshima, Nagasaki and Japan’s Surrender. Begin the book: Part 1 — Prologue.
11 June: James Franck Appears Again
James Franck has appeared twice in our story: first as a professor protesting the persecution of colleagues in Germany, then as a researcher working inside the American atomic undertaking. In June 1945, his name stood above a different intervention. A committee he chaired at Chicago’s Metallurgical Laboratory submitted a report on the political and social consequences of nuclear power. Its subject was not how to complete the next experiment. It was what the achievement might require of the people who possessed it. [1]
The report challenged the idea that an American technological lead would guarantee lasting security. Other countries could acquire the capability. The authors feared that the manner of its first use would affect the possibility of international control. They proposed a demonstration before international representatives rather than a surprise attack as the weapon’s introduction to the world. [1]
The date puts the disagreement in its proper place. The first atomic test had not occurred. These were not objections invented after the effects on Japanese cities became publicly visible. They were arguments about a capability the participants expected to possess.
This changes the question posed at the beginning of our series. Assembling accomplished people could help a country solve an extraordinarily difficult technical problem. It did not ensure that those people would agree on the purpose to which the solution should be put. The successful team was also a community of individuals capable of disagreement.
To understand where their advice could go, we must first return to Washington in April. Before the report could influence a decision, there had to be someone authorised to receive it—and an organisation through which it would be considered.
25 April: A Briefing About More Than a Weapon
A memorandum discussed with Truman on 25 April set out the prospective weapon’s destructive power and the responsibilities accompanying it. Secretary of War Henry Stimson warned that the United States could not expect to preserve an indefinite monopoly. The memorandum also recognised Britain’s participation and urged the President to consider advice about both immediate action and the future. [2]
This was not simply an engineer reporting that a machine was nearly finished. The document placed scientific achievement inside questions of international order and political responsibility. Those questions were being raised within senior government, not only by researchers later described as dissenters.
Its uncertainty matters. The memorandum described an anticipated capability; the full-scale test remained ahead. Government leaders were considering policy while the project was still working towards the evidence that would make the policy practicable.
That overlap is familiar from Part 7. Industrial commitments had been made before every experimental question was resolved. Here, preparations for use were developing before the final demonstration. In both cases, expectations helped cause action. Expectations were not the same as completed results.
A briefing can also contain a warning without guaranteeing that the warning will govern later choices. Noting the danger of an arms race does not establish how much weight a decision-maker ultimately gave it. To find that out, we must follow the subsequent documents rather than treat recognition of a problem as proof that it had been solved.
An Advisory Committee, Not a Single Moment of Decision
In May, Stimson established the Interim Committee with Truman’s approval. It considered wartime use, disclosure and the future organisation of atomic energy. A scientific panel comprising Arthur Compton, Enrico Fermi, Ernest Lawrence and J. Robert Oppenheimer advised it. The committee was a channel for recommendations, not a substitute for presidential and military authority. [3]
These distinctions prevent a misleading picture in which four physicists simply voted and the government obeyed. Scientific advice, a committee recommendation, an executive judgement and an operational order were different acts. Their relationship must be reconstructed rather than compressed into the phrase “the decision”.
A memorandum written by committee secretary R. Gordon Arneson on 6 June summarised the recommendations emerging from the recent meetings. It recorded support for use against Japan as soon as possible, without prior warning, and against a military or industrial installation with homes or other vulnerable buildings nearby. Civilian surroundings were therefore visible in the discussion, not absent from it. [4]
The same memorandum addressed publicity and postwar control. Preparation for public explanation was proceeding alongside preparation for possible use. A secret undertaking would eventually have to be described to people who had not participated in its deliberations.
The document establishes a policy direction. It does not establish that every participant held the same view indefinitely, or that no subsequent objection was considered. A recommendation can become influential without closing every route through which another position might be expressed.
12 June: Forwarding a Report Was Not Endorsing It
The day after the Franck Report’s date, Arthur Compton sent it to the Secretary of War through George Harrison. His covering memorandum explained that the laboratory wanted the argument considered and that time was short. Compton transmitted the report while also identifying objections to its recommendations. [5]
He worried that avoiding military use might prolong the war and cost lives. He also questioned whether the world would accept the sacrifices required for lasting control without seeing the weapon used militarily. These were claims about future political and human consequences, not findings an experiment could verify in advance. [5]
Compton’s position is important because it resists a convenient division between an institution and its critics. He could believe a report deserved attention without accepting its conclusion. Preserving that distinction gives us a more accurate account of how disagreement travelled inside the project.
The proposed demonstration also raised two different questions. Would observers accept that the capability was real? Would Japan’s leaders then make and enforce a decision to surrender? Success at the first task would not automatically complete the second.
That uncertainty does not establish that a demonstration would have failed. It identifies what remained unproved. We should apply the same standard to its advocates and its opponents: neither could produce an observed result from an alternative that had not been tried.
16 June: Scientists Disagreed About What Their Knowledge Required
The scientific panel’s memorandum of 16 June acknowledged a range of views among scientists, from a demonstration to direct military use. Its members supported the latter. They saw no convincing demonstration likely to end the war and hoped military use could save American lives. The memorandum also recommended informing other major powers and opening discussion of future cooperation. [6]
The panel then drew an explicit boundary around its authority. Its members did not claim that creating the weapon gave them ownership of the decision, or special competence in resolving its political, social and military consequences. Expertise about a capability did not settle every question concerning its use. [6]
This is not a reason to dismiss the advice. People who understood the project could identify possibilities and limits that others might miss. But their recommendation concerning Japanese behaviour remained a judgement about people and institutions, not a consequence deduced from nuclear physics.
The comparison with the Franck committee is revealing. Both groups understood that the weapon would affect the postwar world. They reached different conclusions about how its first appearance should be managed. The dispute was not between people who recognised consequences and people who recognised none; it involved different expectations about which consequences were most likely and most urgent.
For our larger thesis, this is a crucial limit. A country may successfully concentrate expertise without producing a single authoritative answer to a moral or political question. The institution must still decide how to hear disagreement and who carries responsibility for the resulting action.
27 June: A Warning Was Another Proposal
Under Secretary of the Navy Ralph Bard proposed a different approach in a memorandum dated 27 June. He favoured warning Japan before use and exploring whether contact, including assurances about the Emperor and Japan’s treatment after surrender, might end the war. He acknowledged that he did not know whether such an approach would succeed. [7]
Bard’s proposal should not be merged with the Franck committee’s demonstration. A demonstration would reveal a capability through an event arranged for observation. A warning could communicate a threat without such an event. Negotiating terms would address the political settlement. These approaches could be combined, but they were not identical.
Nor was Bard simply announcing opposition to every imaginable use under every circumstance. He was proposing another step before use. Understanding the condition matters because the disagreement concerned sequence as well as principle.
This is also why the existence of alternatives should not be treated as a binary question. There was more than one proposal, each with its own purpose and uncertainty. Their advocates did not have to prove success beyond doubt for the proposals to deserve consideration. But a historian cannot turn consideration into evidence that success was assured.
2 July: What Would the Warning Say?
On 2 July, Stimson sent Truman a memorandum concerning the programme for Japan. It discussed the dangers of invasion and proposed a warning explaining the consequences of continued resistance and the conditions of surrender. It suggested that an assurance allowing a constitutional monarchy under the existing dynasty could make acceptance more likely. [8]
The covering letter is important. Stimson said the main paper had been drafted without reference to the new weapon, while suggesting that the warning would probably be associated with its use. The document cannot therefore be presented as an unambiguous demand that every military use be postponed until a separate diplomatic experiment had run its course. [8]
We now reach the same issue from the opposite side of the correspondence examined in Part 12. Japanese officials were debating the institutions they hoped to preserve. American officials were considering what assurances might alter Japanese calculations. Recognising a possible connection was not the same as agreeing to incorporate it in the final declaration.
A proposed reassurance can be consequential even if it is not adopted. Its presence in the record shows that an option was visible to decision-makers. Its rejection or omission still requires explanation; the later outcome does not make the option cease to have existed.
At the same time, a different sentence in an ultimatum would not have acted directly on every Japanese military command. An argument that it would have produced surrender must address authority, agreement and compliance—the political difficulties already visible in the preceding chapter.
4 July: The Partnership Included Consent
The atomic undertaking was not wholly American in its scientific origins or international arrangements. At a Combined Policy Committee meeting on 4 July, British representative Field Marshal Sir Henry Maitland Wilson conveyed his government’s agreement to use the weapon against Japan. The minutes connected that consent to the requirement established in the 1943 Quebec Agreement. [9]
This adds a political dimension to the cooperation described in Part 6. Sharing expertise could create a relationship that extended beyond laboratory work. Governments also negotiated the terms under which the resulting capability could be employed.
British consent was not the American military order that followed later in the month. Nor does a Canadian member’s presence at the committee establish that every participating government exercised identical authority over each decision. The minutes identify particular roles; we should not replace them with an undifferentiated coalition.
The sequence again matters. An important international approval preceded the first full-scale atomic test. Scientific uncertainty and political preparation were developing together. The blast did not begin the entire decision process.
16 July: What Trinity Demonstrated
At approximately 5:30 in the morning, Mountain War Time, on 16 July 1945, the first atomic test took place at the Alamogordo Bombing and Gunnery Range in New Mexico. Known as Trinity, it provided a physical demonstration of the capability towards which years of scientific and industrial work had been directed. [10]
The result mattered enormously to the undertaking we followed through Parts 5–8. A scientific warning had helped obtain attention; institutions had mobilised research; industrial organisations had committed resources; communities had sustained the people doing the work. The test was evidence of what those connected efforts could now produce.
Yet the category of the result must remain clear. An experiment demonstrated an explosive capability. It did not test the response of the Japanese government to a particular warning, demonstration or attack. It did not compare the possible endings of the war under controlled conditions.
The proposed international demonstration discussed in June was therefore not simply accomplished by Trinity under another name. Audience and purpose matter. Establishing a result for the project was different from presenting it to foreign representatives as part of an attempt to change diplomatic choices.
Technical success can intensify a decision rather than answer it. Before success, an option may be hypothetical. Afterwards, someone must decide what to do with a real capability. The achievement changes the circumstances of responsibility; it does not remove responsibility.
The Desert Was Not Outside Human Society
Trinity is often pictured as an isolated event in an empty landscape. The National Park Service’s history of the downwind communities records that civilians lived in the surrounding region and were not warned in advance about the test. A cover story attributed the explosion to an ammunition accident. Residents encountered an event whose nature the authorities were withholding from them. [11]
The distinction between distance from a test point and absence of consequences is important. A boundary around a military site does not necessarily contain every effect produced inside it. People living beyond it can become part of the event without having been included in its decisions.
Medical officer Stafford Warren’s report of 21 July discussed the monitoring of radioactive material and the potential hazard beyond the controlled area. His recommendations included using a more isolated location for any similar future test. The report is evidence that concern existed within the project soon afterwards; it is not a comprehensive long-term health study of everyone exposed. [12]
We should not turn limited wartime monitoring into a precise total of later illnesses that the document cannot establish. Neither should uncertainty about that total erase the problem of exposure without warning. The questions concern both what happened physically and what people were permitted to know.
Secrecy, examined inside the project communities in Part 8, now had another distribution. Some people could study and discuss the event because their work placed them within the security boundary. Other people experienced possible consequences without access to the same explanation. An institution could succeed at concealing its activity while leaving those outside it less able to understand their circumstances.
17 July: A Petition With a Condition
Szilard and fellow scientists signed a petition dated 17 July asking Truman to withhold atomic attacks until Japan had received publicly stated surrender terms and an opportunity to accept them. Even after a refusal, the petition urged careful consideration of the moral responsibilities involved. It warned that introducing this form of warfare would affect the country’s position in the world that followed. [13]
The date falls one day after Trinity, but that does not establish that seeing the test caused the petition. An earlier version dated 3 July survives. The effort was already developing before the explosion. Chronological proximity cannot replace evidence of a causal connection. [13]
The final text also deserves to be read as written. It was not simply a demand that no atomic weapon could ever be used under any imaginable circumstances. It imposed conditions and asked the President to exercise responsibility. Turning a conditional argument into an absolute one changes the position its authors actually advanced.
Szilard’s return to the narrative gives this moment particular force. In Part 5, he helped bring a warning about a possible weapon to presidential attention. Now he was trying to influence how the capability would be used. Support for developing a response to a feared danger did not bind every participant to endorse every later application.
The continuity is a problem of responsibility, not proof that Szilard always possessed the right prediction. A person can revise the action they advocate as circumstances change. Whether the revised proposal would work remains a question to examine rather than a conclusion guaranteed by the person’s earlier insight.
A Message Addressed to the President Did Not Necessarily Reach Him
The petition did not reach Truman before Hiroshima. The documentary history preserved by the National Security Archive and the Atomic Heritage Foundation distinguishes its preparation and circulation from its receipt by the President. We should not describe Truman as reading this particular petition and rejecting it when the evidence does not support that sequence. [14]
This does not mean that Truman had encountered no discussion of alternatives. It means that one specific document failed to arrive before the relevant action. The history must keep those statements separate.
There is a revealing contrast with the routes followed earlier in the book. Einstein’s signature, Szilard’s initiative and Alexander Sachs’s access had helped a warning reach Roosevelt in 1939. In 1945, a petition bearing researchers’ names did not complete the same journey merely because it was addressed to the President.
Institutions can organise information effectively for one purpose and obstruct it for another. Moving research results towards a usable capability is not identical to moving objections towards the people empowered to reconsider its use. The existence of the first route does not prove the effectiveness of the second.
That conclusion does not require us to invent the private motives of everyone handling the paper. It identifies a demonstrable difference between expression and influence. The scientists could formulate an argument; their position inside the organisation did not guarantee an audience with final authority.
Potsdam: Two Expectations in the Same Diary
Truman’s Potsdam diary records his expectation on 17 July that Soviet entry would contribute decisively to ending the war. The following day, he expressed confidence that Japan might surrender before that entry and associated that expectation with the new atomic capability. These entries are contemporary evidence of hopes and assessments involving more than one possible pressure on Japan. [15]
They should not be turned into a record of what later caused surrender. A diary entry about an anticipated event establishes what its author wrote at that moment. It does not demonstrate the event’s actual effect before it has occurred.
The entries also complicate simple explanations of motive. A leader could expect military advantage from a weapon, consider the effect on the war’s duration and contemplate the relationship with another major power. Those considerations need not be mutually exclusive. Establishing their relative weight requires a broader reading than selecting the most convenient sentence.
Our previous chapter showed Tokyo seeking Soviet mediation while Moscow had committed to entering the war. Here, Truman’s writing shows the same international setting viewed from Washington’s side. The governments were not waiting inside a laboratory experiment whose variables could be held constant. Diplomacy, military preparations and the new test result were changing together.
25 July: Military Language and Civilian Surroundings
In his 25 July diary entry, Truman described his intention that military objectives and service personnel, rather than women and children, should be targeted. That statement must be read beside the documents describing contemplated urban use, including Arneson’s June memorandum. The President’s wording does not establish that the eventual operation could separate an installation from the population around it. [15] [4]
A location can contain military facilities and civilian homes simultaneously. Calling it militarily important answers one question about its role. It does not tell us that everyone likely to be harmed is a combatant.
The gap between these descriptions is historically important even where the sources do not reveal exactly how every participant understood it. We can identify the different language without claiming access to Truman’s entire private understanding or assuming that an entry in his diary changed the physical effects of the weapon.
It would be equally misleading to treat every use of the word “military” as empty. Industrial and command functions mattered to planners. The necessary correction is not to deny their existence, but to recognise that their existence did not remove civilian life from the place being considered.
This is where description becomes part of responsibility. Administrative language can help people specify a task, but it can also make some consequences less visible. A historical account must restore the people who disappear when a city becomes only a category in a document.
The Written Directive
Also dated 25 July was the directive from Acting Army Chief of Staff Thomas Handy to General Carl Spaatz. It authorised the first atomic attack after approximately 3 August, subject to suitable conditions, against one of four listed cities: Hiroshima, Kokura, Niigata and Nagasaki. It further authorised additional bombs as they became ready. [16]
The document was signed by Handy and stated that it was issued with the direction and approval of the Secretary of War and the Army Chief of Staff. It reserved public information about the weapon to the Secretary and the President. It was an instruction for action, not another request that a committee examine the possibility. [16]
Its scope matters. The surviving order did not authorise only one attack and then require the same decision process to begin again from nothing. Nor should its signature be described as Truman’s signature. A chain of authority connects political responsibility and military execution; the name signing a particular document is one part of that chain.
The distinction is not an attempt to disperse responsibility until nobody possesses it. It identifies who recommended, who approved and who was instructed to act. Clear attribution makes responsibility more intelligible than placing every action into the hands of one symbolic individual.
An authorisation also differs from an irreversible natural event. Orders can be amended or withdrawn, even when preparations have advanced. Once issued, however, an order establishes a course of action that will proceed unless conditions or further instructions intervene. The institutional question has shifted from whether a capability should be considered to how an authorised action will be carried out.
26 July: A Public Ultimatum Was Not a Specific Atomic Warning
The Potsdam Declaration appeared the next day in the names of the United States, the Republic of China and Great Britain. As Part 12 showed, it called for the surrender of Japan’s armed forces and set out occupation and postwar provisions. It threatened destruction, but it did not identify an atomic bomb or explicitly assure the Emperor’s continued position. [17]
The declaration must therefore not be presented as though it carried every warning or assurance proposed in June and early July. A demand to surrender, a disclosure of a particular weapon and a statement about a particular political institution are different forms of information.
The ordering of the dates is equally important. The military directive preceded the declaration. That fact establishes that preparations for use were not first conceived only after Japan’s response to the public ultimatum. It does not, by itself, establish that no subsequent response could have changed the course of action.
We have now joined the two narratives. Part 12 approached July through Japan’s military crisis and diplomacy. This chapter approached it through American scientific achievement, recommendations and authority. At this point, the documents belong to the same unfolding situation, though their authors did not share complete information or a common set of purposes.
Alternatives Existed. Their Outcomes Were Not Known.
The record contains a proposed demonstration, prior warning, clearer surrender terms and continued debate about the effect of other military pressure. It is therefore inaccurate to say that nobody considered another course. It is also inaccurate to convert the existence of a proposal into proof of the outcome it would have produced.
Several questions must be distinguished. Was an alternative technically possible? Was it considered politically or militarily acceptable by the people with authority? Would it have secured an authorised Japanese surrender, and on what timetable? What harms might occur while waiting? Those questions require related but different evidence.
The rejection of an option answers what the decision-makers chose. It does not automatically prove that the rejected option would have failed. Likewise, a proposal’s moral attraction does not supply evidence that the opposing government would have responded as its advocates hoped.
Our standard should be consistent across the comparison. Claims that military use was certain to end the war, or that a demonstration was certain to do so without an attack, both go beyond what the July documents could establish. Contemporary actors made consequential judgements without possessing certainty. A later account should explain those judgements rather than manufacture certainty on their behalf.
Uncertainty does not prevent ethical evaluation. It changes the questions that evaluation must address: the evidence available, the risks imposed, the people affected, the opportunities considered and the responsibilities of those deciding. Acknowledging uncertainty is not the same as declaring every choice equally defensible.
The Achievement Could Not Answer for Its Use
The original thesis asked whether America assembled intelligent people, won the war and acquired a lasting advantage. This chapter reaches a point at which the answer requires more than an account of successful mobilisation.
The scientific undertaking had produced a new capability. It had also produced people who questioned its proposed use, people who supported that use and institutions that gave their recommendations different routes to authority. Cooperation in developing the weapon did not erase disagreement about what should follow.
The distinction changes what we mean by institutional success. An organisation can succeed at completing its assigned technical task while leaving serious questions about the task’s purpose, the treatment of affected communities or the hearing given to objections. These are not necessarily measurements of the same performance.
Nor should the arguments about postwar security be dismissed as concerns for a later book. They were already part of the decisions of 1945. We can acknowledge their presence here without prematurely claiming that any participant had accurately predicted every feature of the subsequent nuclear age.
The most defensible conclusion is specific. Knowledge helped create the capacity to act. It informed some judgements about how to act. It did not determine the action by itself or remove the authority of governments and military institutions. The consequences arose from people choosing what to do with a capability, not from a scientific result issuing its own command.
At the Threshold of August
We began with Franck’s warning about the world that might follow a technical success. We then followed briefings, recommendations, a petition, a test, a diary and a military directive. Each document did something different. Combining them reveals a decision process; treating them as interchangeable would conceal it.
By the end of July, the new capability had been demonstrated, international consent had been obtained from Britain, military use had been authorised and Japan had received a public declaration of surrender terms. The next events would test political expectations in a way no laboratory could reproduce.
Part 14 opens inside Hiroshima’s damaged Red Cross Hospital, then follows Soviet entry, Nagasaki and the Japanese decisions that led to surrender. It distinguishes the sequence of events from arguments about their relative importance and follows the diplomatic exchanges through the September signing. Neither a single explosion nor a single statement is made to stand for the whole ending.
Trinity showed that the project could produce an atomic explosion. What people chose to do next was not a result contained inside the experiment.
Continue to Part 14 — August 1945: Hiroshima, Nagasaki and Japan’s Surrender. Reading order: Part 12 — Japan before the atomic bombs → Part 13 — Trinity and the decisions before Hiroshima → Part 14 — Hiroshima, Nagasaki and Japan’s surrender. The main series continues before the prequel, the sequel to the present and the final hub.
Sources and Chapter Notes
The principal narrative covers April–July 1945. The June opening is followed by an explicit return to April. Recommendations, petitions, receipt of documents, tests, authorisations and actual attacks are distinguished. Primary documents are read as evidence of what their authors recorded or advocated, not automatic proof that their predictions were correct. The chapter does not calculate an alternative surrender date or reproduce technical weapons instructions. Its account of Trinity’s neighbouring communities does not claim a precise long-term health toll.
[1] Franck committee (11 June 1945). Report on Political and Social Problems, Metallurgical Laboratory, University of Chicago. Primary text transcribed from National Archives, Record Group 77, Harrison-Bundy files, folder 76. Used for the committee’s policy argument and demonstration proposal; its technical estimates and speculative future scenarios are not reproduced.
[2] Stimson, Henry L. (25 April 1945). Memorandum Discussed with the President. Primary document reproduced by the National Security Archive. The three-page facsimile was inspected; its anticipated capability is not described as a completed test result.
[3] Atomic Heritage Foundation / National Museum of Nuclear Science & History. Interim Committee. Institutional historical account used for the advisory structure and membership. The specific recommendations are checked against the contemporary memorandum in [4].
[4] Arneson, R. Gordon (6 June 1945). Memorandum to George Harrison. National Archives, RG 77, Manhattan Engineer District records, Harrison-Bundy files, folder 100; reproduced by the National Security Archive. Both facsimile pages were inspected. A summary of committee recommendations is distinguished from the later operational directive.
[5] Compton, Arthur H. (12 June 1945). Covering Memorandum Transmitting the Franck Report. National Archives, RG 77, Harrison-Bundy files, folder 76; reproduced by the National Security Archive. The first page was inspected for the transmission and Compton’s stated reservations. Forwarding the report is not treated as endorsing every recommendation.
[6] Scientific Panel (16 June 1945). Recommendations on the Immediate Use of Nuclear Weapons. Primary memorandum transmitted by Oppenheimer for Compton, Fermi, Lawrence and himself. Both facsimile pages were inspected. Searchable transcription.
[7] Bard, Ralph A. (27 June 1945). Memorandum on the Use of the Atomic Bomb. Primary text reproduced by Atomic Archive. The proposed warning and diplomatic contact are distinguished from a permanent prohibition on every possible use.
[8] Stimson, Henry L. (2 July 1945). Memorandum for the President: Proposed Program for Japan, with covering letter. Foreign Relations of the United States, Potsdam Conference, Volume I, document 592. The qualification in the covering letter is read alongside the proposed assurances in the main paper.
[9] Combined Policy Committee (4 July 1945). Minutes of a Meeting. Foreign Relations of the United States, Potsdam Conference, Volume I, document 619. Primary record of British consent and its relationship to the Quebec Agreement.
[10] National Park Service. The Trinity Test. Used for the date, approximate local time and location of the first atomic test, not as proof of the political effect of a hypothetical demonstration to Japan.
[11] National Park Service. Trinity Test Downwinders. Historical account of surrounding communities, secrecy and the absence of an advance civilian warning. Present-day compensation rules and unsupported numerical estimates of illness are outside this chapter.
[12] Warren, Stafford L. (21 July 1945). Report on Trinity Radiological Monitoring. Primary report in transcription, particularly its concluding assessment and recommendations. Wartime monitoring and reassurance are not substituted for a comprehensive later exposure or health study.
[13] Szilard, Leo, and fellow scientists. Petition of 3 July 1945 and Petition to the President, 17 July 1945. Primary texts; the final petition’s first page was inspected in facsimile. The earlier version establishes that the initiative preceded Trinity. Different drafts and signature totals are not conflated.
[14] Atomic Heritage Foundation / National Museum of Nuclear Science & History. Szilard Petition; National Security Archive, document description accompanying [13]. Used for the distinction between the petition’s circulation and its failure to reach Truman before Hiroshima.
[15] Truman, Harry S. Potsdam Diary, July 1945, edited transcription published in the Foreign Service Journal, July–August 1980, and reproduced by the National Security Archive. Printed pages 33–34 were inspected for the entries of 17, 18 and 25 July. The contemporary entries are distinguished from the later editor’s explanatory additions and from evidence of eventual causation.
[16] Handy, Thomas T., to Carl Spaatz (25 July 1945). Directive for the Use of the Atomic Bomb. Primary text transcribed from National Archives, RG 77, with an image of the signed original from RG 342. Used for the authorisation’s timing, scope and stated authority, not operational or technical instructions.
[17] Potsdam Declaration, 26 July 1945. Primary text in the World and Japan Database, National Graduate Institute for Policy Studies and University of Tokyo. Its general threat is distinguished from a specific disclosure of an atomic weapon; its political provisions are read together rather than reduced to a slogan.