Bookmark and Share

N.B.: In Spring of 1981, as part of an assignment for History 111B – The American Nation, 1865-Present, the following paper was submitted as though it was written by a scientific liaison to President Truman at the July 1945 Potsdam Conference. Naturally, to keep within the time frame, the preceding character had many limitations. Scientists, even important ones like Oppenheimer, had no inkling of the military situation and were not informed of the diplomatic situation.14 For this reason, the character does not discuss the political ramifications of outdoing the Soviets because he would not know of the oncoming break in relations. Every attempt was made to draft this hypothetical report in the manner which a science writer in July of 1945 would have written it. This was done by diving into various science-oriented and news-oriented periodicals during that period. Please remember, the language of this fictitious report may seem naïve, ignorant, or even offensive by today’s standards, but it reflects what was known and thought on July 17, 1945.


* * * * * SECURITY 1 PRIORITY * * * * *






17JULY 1945



It is the purpose of the following report to outline the recent developments concerning the Manhattan Project. As you may or may not be aware of, Mr. President, American scientists successfully detonated an atomic device 0530 yesterday morning, 16July 1945, at Jornada del Muerto, the northeast region of the Alamogordo bombing range in New Mexico. The report will contain: 1) a brief description of the device; 2) an account of the probably destructive effects of the weapon; and 3) proposals and recommendations of war and post-war use of atomic energy. Security officials have been debriefed and will advise you as to what developments should be revealed to all allies.

Respectfully Submitted,

Christopher Carosa

Professor of Physics and Scientific Liaison to the Interim Committee at Potsdam.

17July 1945




The story of the atomic bomb has been the greatest and best kept secret of the war.1 The first big explosion of the atomic age occurred in January 1939. At the Kaiser Wilhelm Institute in Berlin, Dr. Otto Hahn successfully and unexpectedly split the atom of an extremely rare form of Uranium—the isotope U235 (see figure 1). Proportionally the greatest man-made explosion, the fission reaction produced 200 million electron-volts. In everyday terms, it would take 25,000 billion fissions like this to produce one horsepower. News of the German fission research, plentiful for months, abruptly stopped, the victim of Nazi military censorship. Nazi Germany had the jump on the rest of the world in the subsequent atomic race. Imagine the terror and destruction Germany would have implemented had they placed atomic warheads on their V-2 rockets. This would have been the case had not British and Norwegian commandos raided and destroyed a German heavy-water plant.* Aided by the commandos, U.S. scientists broke ahead of the German research.

* At this point in time, the Germans were on the verge of a major discovery. The use of “heavy-water”—water with a rare form of hydrogen—was essential to this discovery.The Neutron bullet at the top splits the U235 nucleus A into fragments I and II and, in addition, emits three extra neutrons. One of the latter may hit another U235 nucleus B, and split into fragments C. Each of the original fragments may break down into D.2

The most obvious difference between the explosion of an atomic bomb and that of a conventional bomb is the magnitude. Each of the two available atomic bombs represents the equivalent of 20,000 tons of TNT. What causes this vast difference in power? Whereas TNT bombs merely rearrange the atoms, atomic bombs change the atoms’ identities via the fission process. Fission transforms much of the explosive mass—usually U235 or Plutonium—into energy. One uses Einstein’s formula (E=mc2) to calculate the total energy. The significance of the equation is immediately apparent when one remembers that the speed of light (c) is 186,000 miles-per-second. To emphasize the difference between chemical reaction and mass conversion energies, let’s compare the two. The energy gained from exploding one pound of TNT is equivalent to the amount of energy needed to raise 36 lbs. of water from freezing (32°) to boiling (212°). With nuclear fission, one pound of U235 would produce an equal temperature rise in over 200 million pounds of water.3

What makes atomic bombs totally different from conventional bombs? Atomic bombs release lethal radiation. There is much disagreement as to the effect and intensity of the radiation (q.v. Section II). From the available data, there is at least a danger of harm during the initial explosion. In short, radiation comes in two blasts. First, there’s an extremely intensive burst lasting only 3 milliseconds. A less intense one of a much longer duration lasting several seconds followed this. The first burst comprises the more biologically destructive ultraviolet radiation. The second contains over 90% light energy (radiation from the visible part of the spectrum).

Below is a sketch of the probable design of the bomb.SECTION II. THE EFFECTS OF THE A-BOMB vs. CONVENTIONAL BOMBS

Mr. President, let me restate the power of this new weapon. On 6December 1917, the munitions ship Mont Blanc, carrying 3,000 tons of TNT, exploded in the harbor of Halifax, N.S. The explosion killed in excess of 1,100 people, completely destroyed two square miles of the city, and was heard over 150 miles away. A single atomic bomb can do approximately seven times as much damage.4 To clarify the point, yesterday, with the successful completion of Project Trinity, we have some hard facts when discussing the power of the atomic bomb. When the bomb was detonated, there was a tremendous and sustained roar in Albuquerque, 120 miles away. The sky was as bright as midday; scientists close by could see a huge, multicolored pillar of cloud rising 40,000 feet into the sky; and at ground zero, there was nothing but an enormous crater—the steel support tower had completely vaporized! It should be noted here that Dr. Hans Bethe, a member of the Manhattan District Project on loan from Cornell University, predicted many of these effects months before the test was carried out.

Now, Mr. President, before I advise you on the use of such a weapon, let me quickly go over the damage and casualty estimates. The atomic blast differs from the conventional blast in three ways: 1) mass distortion of buildings—a common bomb can damage only portions of large buildings, whereas an atomic bomb, like a great hand, can shove over even the largest of buildings; 2) downward thrust—because an atomic blast is well up in the air, much of the damage results from downward pressure (this is especially effective on buildings with flat roofs); and 3) the long duration of the positive-pressure pulse and consequent small effect of the negative-pulse or suction.5

Radiation also prompts severe damage and casualties. The radiated flash heat will ignite light, flammable objects, although the subsequent pressure blast will blow out these. These two effects should combine superbly on the light construction of the Jap houses. Personnel within about 4,000 yards can experience a skin temperature rise of 90° in the first millisecond of the explosion. This is what we do know about the radiation produced by such devices.

We also know, and fear, that deadly and poisonous isotopes are the product of fission reactions. Many of the elements (e.g., strontium 90) have incredibly long half-lives, (i.e., they last more than a million years). At this time, it is not known how long an affected area would remain biologically dangerous. For all we know, all those working on the Manhattan project, including myself, might already be fatally affected.

In conversations with my esteemed colleague, Major General L.R. Groves, he apparently intends to conduct field exercises using atomic devices with several army units. Due to the unknown nature of radiation, I strongly advise against such maneuvers for 5 or 10 years, so further study of this phenomenon could take place.

Graphs A and B deal with the immediate death estimates (percentages).6 Projections of delayed deaths would be purely conjectural due to our lack of knowledge of the delaying effects of radiation. Delayed deaths also include many victims who would die due to lack of proper medical care as the hospital facilities and the transportation routes will be destroyed by the bomb. The figures assume an average amount of natural protection (e.g., hills) and optimum weather conditions.

GRAPH A – Percentage of Mortality vs. Distance from Ground Zero


100  *(100)

90                    *(93)    *(92)

80                                            *(86)

70                                                        *(69)


50                                                                    *(49)


30                                                                                *(31.5)


10                                                                                            *(12.5)

0                                                                                                          *(1.3)*(0.5)*(0.00)

0          1          2          3          4          5          6          7          8          9          10

Distance in thousands of feet

GRAPH B – Projected Cause of Immediate Death

Cause:             % of total:

Burns               *************************** (75)

Flying Debris  ******* (20)

Flying Glass    * (4)

Other               *** (8)


The following section deals with war and post-war options concerning the atomic bomb and atomic energy. I will touch on the use of post-war atomic energy only briefly, for obvious reasons. First, let me point out my recommendations. I do not advocate the use of the bomb until all other diplomatic options are exhausted. Furthermore, and in agreement with Niels Bohr and other American scientists, I propose we try to set up a framework whereby an international committee will be in charge of atomic control before we use the bomb.7 This, of course, means collaborating with the Russians. From what I gather, we have nine options: 1) change the unconditional surrender formula; 2) institute a naval blockade; 3) wait for the Russians to declare war; 4) warn of Russian intervention; 5) demonstrate the bomb; 6) warn that the bomb will be used unless the Japs surrender; 7) use the bomb; 8) a shock assault on the island of Kyushu; and 9) a full-scale invasion. Implementing the latter two (31,000 and 5000,000-1,000,000 estimated casualties, respectively) would be unfair to our boys; hence, these are the only two options I would put behind the use of the bomb. As Acting Secretary of State Grew, Secretary of the Navy Forrestal, and Secretary of War Stimson all urge, I believe the first option would end the war. In issuing any proclamation to the Japanese government, however, it is imperative to include the signature of the Russians. I overheard military personnel discussing the intelligence reports which indicate the Japs fear Russian intervention.

Robert Oppenheimer, head scientist of the Manhattan Project, drafted the report issued by the Interim Committee’s Scientific Panel last month. In it, he said he, “doesn’t know beans about the military situation in Japan,” and believes the technical demonstration of the bomb would not end the war. The report, which I agree with, is in discord with the recommendations of the Franke Committee and Special Assistant to the Secretary of the Navy Lewis Strauss. My reasoning puts me in agreement with our civilian consultant when he says the Japs will fight to the end. However, I still disagree with his naïve and uninformed sentiment which mandates the use of the atomic bomb. It is obvious that he is not aware of the present diplomatic situation. We should note that military consultants, including SAV General Eisenhower, believe the use of the bomb is unnecessary.9

To summarize, it is the opinion of most of your advisors, save Secretary Byrnes and our spokesman for the public, that the use of the bomb, despite its obvious shock value, is no longer of military need. However, it is recommended that any one or a combination of the first six options be used before the bomb is dropped. The only advantages I see in using the bomb is that the scientific community will get good press. In addition, quite possibly in viewing the mutilation and destructive power of the weapon, the world’s politicians will get together and strive to end the war.

Finally, I am resolved to accept any decision involving the military use of the weapon. Unlike the colleagues of Sir James Chadwick, who refused to work on the Manhattan Project for fear of creating a “destroying monster,”10 I and the Manhattan scientists take the view of Albert Einstein. Although we have pacifistic intentions, it is absolutely necessary to stop the tide of fascism.

Concerning post-war decisions, I believe now is not the time to discuss the issue in depth. It is probable that someday, within the next generation, a spoonful of uranium will replace the binful of coal or tank of oil in our cellars.11 However, what is imminently necessary is a politically free institution, much like the League of Nations. This organization should control the use of atomic power. As Niels Bohr says:

Against the new destructive powers, no defense may be possible. The issues center on worldwide cooperation to prevent any use of the new source which does not serve mankind as a whole.12

However, I believe that in time, the discovery will immensely increase the ease of human life. To use the technology fruitfully will be an increase to man’s own spirited resources. Men must become better, that’s the moral.13


  1. TIME Magazine, August 13, 1945 p.21
  2. SCIENTIFIC AMERICAN, October 1945 A.P. Peck p.238
  3. The Secret History of the Atomic Bomb, Brown & MacDonald, p.569
  4. TIME, Aug. 13, 1945 p.66
  5. Brown & MacDonald, p.571
  6. Ibid, p.567
  7. Gar Alperovitz, Cold War Essays, P.67
  8. Ibid, p.59
  9. Ibid, p.63
  10. TIME, Aug. 20, 1945 p.36
  11. SCIENTIFIC AMERICAN, Oct. 1945 p.241
  12. TIME, Aug. 20, 1945 p.36
  13. Ibid, p.36
  14. Alperovitz, pp.59-60


Speak Your Mind


Skip to content