Isegoria

August 1, 1945 came and passed, General Groves explains (in Now It Can Be Told: The Story of the Manhattan Project), and the weather was not favorable over Japan. General LeMay did not think that it would be wise to undertake the mission under those conditions:

The six crews that might be used were given special instructions on the procedures they were to follow, and at another briefing on August 4, Parsons explained the effects they could expect when the bomb exploded. Most of them knew by now that they were dealing with a special type of bomb, but Parsons’ statement that the force of the explosion would be equivalent to that of twenty thousand tons of TNT came as a complete surprise.

During the period of waiting, the special air-sea rescue plans were settled. They emphasized that no other aircraft would be permitted within fifty miles of the target during a period of from four hours before until six hours after strike time. Not even for rescue operations would this restriction be lifted. Special air-sea rescue facilities were to be provided by both Army and Navy planes and by submarines, and in spite of the necessary restrictions we had placed upon it, rescue coverage in this operation would be far better than average.

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Other air attacks on Japan were to be carried out on the same day as our mission, to divert any Japanese defense actions that might endanger our operation. Hiroshima would be the primary target, with Kokura Arsenal and Kokura the secondary targets, and Nagasaki the tertiary target. The aiming point for Hiroshima was close to the Japanese Army Headquarters.

Hiroshima was a highly important military objective. The Army Headquarters was located in a castle. Some 25,000 troops were in its garrison. It was the port through which all supplies and communications passed from Honshu to Kyushu. It was the largest city, excepting Kyoto, that was still undamaged by American air raids. Its population was believed to be over 300,000, and it was a beehive of war industry, carried on in moderate-sized plants and in small shops as well as in almost every home.

We would use a total of seven planes. One would be sent to Iwo Jima to serve as a spare in case the bomb-carrying plane developed mechanical troubles on the flight from Tinian. Three planes would go ahead, one to each target area, to appraise the local weather and to relay the information back to the bomb-carrying plane, which would be accompanied by two observer planes to the general vicinity of the target. One of these carried special measuring and recording instruments, including some that would be dropped near the target to radio back their readings.

Radar was to be used as an aid but the actual bombing was to be accomplished visually. If this proved to be impossible, the bomb was to be brought back, probably to Iwo Jima, as the plane’s gas supply might not permit the return to Tinian. We were anxious to avoid having it come down at other air bases, for in case of a landing accident we wanted personnel on the ground who would be aware of the special precautions that would have to be taken.

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Provisions were also made for the strike photographs to be taken by the 3rd Photo Reconnaissance Squadron and two photo crews were briefed on their assignment by the 509th’s intelligence officers.

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Parsons had decided with Farrell’s approval to complete the final assembly of the bomb after takeoff. His purpose was to minimize the hazards of a crash on Tinian. I had previously said that I was opposed to this as unwise, because it was unnecessary and because it would be very difficult to do it in cramped conditions in the plane. I was not informed of the plan until it was too late to interfere.

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The original scheduled time was 0915. Thus, in a flight of some seventeen hundred miles taking six hours and a half, Colonel Tibbets had arrived on target only one-half of a minute off schedule.

The 20th Air Force order covering the operation prescribed a turn of 150° after the bomb was released in order to gain a maximum distance from the point of explosion; such a turn, our studies indicated, could be made without undue risk to the plane and its crew.

Immediately after the bomb was dropped from 31,600 feet, the plane began its getaway maneuver. The flash was seen during this turn and fifty seconds after the drop, the shock waves hit the plane. There were two of these, the first the direct shock wave and the second the reflected wave from the ground. By that time the plane was fifteen miles away from the burst.

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The crews of the strike and the two observation aircraft reported that five minutes after release a dark gray cloud of some three miles in diameter hung over the center of Hiroshima. Out of the center of this grew a column of white smoke which rose to a height of 35,000 feet, with the top of the cloud being considerably enlarged.

Four hours after the strike, the photo reconnaissance planes found that most of the city of Hiroshima was still obscured by the smoke cloud, although fires could be seen around its edges.

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Pictures taken the following day showed that 60 per cent of the city was destroyed.

The area devastated at Hiroshima was 1.7 square miles, extending out a mile from ground zero. The Japanese authorities estimated the casualties at 71,000 dead and missing and 68,000 injured.

The most important result achieved by the Hiroshima bombing was not the physical damage, although over 50 per cent of the buildings were totally destroyed, nor was it the fifteen to twenty thousand Japanese soldiers who were killed or severely wounded, nor was it the thousands of other people killed and injured. The important result, and the one that we sought, was that it brought home to the Japanese leaders the utter hopelessness of their position. When this fact was re-emphasized by the Nagasaki bombing, they were convinced that they must surrender at once.

Parsons reported (in special one-time code, of course):

Results clearcut, successful in all respects. Visible effects greater than New Mexico tests. Conditions normal in airplane following delivery.

Received at the same time was this message relayed from the plane:

Target at Hiroshima attacked visually. One-tenth cloud at 052315Z. 3 No fighters and no flak.

The Alamogordo test, General Groves explains (in Now It Can Be Told: The Story of the Manhattan Project), had not set aside all doubts about the bomb:

It proved merely that one implosion-type, plutonium bomb had worked; it did not prove that another would or that a uranium bomb of the gun type would. We had made every possible component test we could think of. We were reasonably sure of each one. We knew we could bring the U-235 portions of the bomb together in such a way that, if the theories of atomic energy were correct and U-235 behaved as plutonium had, the bomb should go off. But still no test had been made of the complete bomb. Nevertheless, the indications for success were strong enough so that no one urged us to change our plans of dropping the first gun-type bomb in combat without prior test. In any case, we simply had to take the chance, because the production of U-235 was so slow, even compared to plutonium, that we could not afford to use it in a test.

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Early in the morning of July 16, the bomb — minus the last necessary bit of U-235 — was put aboard the cruiser Indianapolis, which sailed almost immediately. The Indianapolis had a fast but uneventful trip through Hawaii to Tinian.

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The Indianapolis arrived at Tinian on July 26 and discharged her cargo that same day. She then put out to sea, headed for the Philippines, but her voyage came to a sudden and tragic end on July 30 when she was attacked by a Japanese submarine and went down with some nine hundred of her crew.

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I had arranged with Lieutenant General H. L. George, the head of Air Transport, for the final parts, including some U-235, of the Hiroshima bomb to be flown from Albuquerque to Tinian. Because I did not want to risk having the plane disappear in flight with an extremely valuable though small piece of U-235, I asked for two large cargo planes in perfect condition, and the best possible crews. I told George that the cargo would be almost infinitesimal and that the second plane was wanted just in case of need, to tell us where the first one crashed — if it did. George had had his orders from Arnold and he simply said, “Whatever you want, you get.”

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The flight to San Francisco was uneventful but when they were about forty-five minutes out over the Pacific, de Silva’s plane had to return to the mainland because of engine trouble. Contrary to what I had counted on, Taylor’s plane, instead of returning too, continued directly to Hawaii and arrived there several hours before de Silva’s plane came in. Despite our desire to keep the flight inconspicuous, a radio tip — probably sent unofficially — alerted Hawaii to a very important flight, and Taylor was met at the airfield by a group of senior officers who expected at least one high-ranking general with entourage instead of a single second lieutenant. Taylor had no written orders with him, since they were in de Silva’s hands, and soon found the local personnel determined, in accordance with custom, to load the empty plane to capacity. Fortunately, the plane crew had been convinced before departure from California that the trip was most unusual and with their support he was able to keep the ship unloaded until de Silva arrived. From then on the trip was uneventful.

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One of our big problems had been whether to use each bomb as it became available or to store up a sufficient number to permit their employment in quantity. Most professional soldiers will go to almost any length to avoid piecemealing away their resources. However, in this case, we felt that the considerations of time and expected power justified our using the weapons as they became available. If our assessment of these factors had been erroneous, our position might very well have been extremely embarrassing, for our projected production rates called for one Fat Man of the type we had tested at Alamogordo (but not by an air drop) to be delivered at Tinian on about August 6, with a second one to be ready about August 24, and additional ones arriving in increasing numbers from there on.

As I have said, we had no assurance that a uranium bomb, the Thin Man, would work at all. Yet, that was the weapon that we employed against Hiroshima, since we had used up our entire immediate supply of plutonium in the test bomb.

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General Marshall was also furnished with the probable readiness dates of the implosion bomb, and I explained that there would have to be a gap of at least three days between successive bombs, no matter what type was used. I did not give him the reason for this: we needed the time to assemble the bomb, and nothing should be hurried. Judging by the Alamogordo test, I said, we now expected this bomb to have an explosive force exceeding the equivalent of ten thousand tons of TNT and possibly reaching as high as thirty thousand tons.

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Many small problems arose as the date of the first bombing approached. Two years before, the War Department had issued orders prohibiting persons with knowledge of future military operations from flying over enemy-held territory. The reason for this order was sound — to prevent leakage of information through possible prisoners of war — but it created an impossible situation for us. We had to have Parsons and Ashworth and their two technical assistants aboard the bombing planes. We also needed Tibbets and his best pilots on these flights, and we wanted to have certain scientists in the observation planes. We simply could not operate under such a restriction.

When this problem was brought to my attention in Washington, I immediately secured War Department authority to disregard the prohibition for both civilian and military personnel concerned with Centerboard, as our overseas operation had been named, provided their flights were essential.

Throughout the period when they were planning the atomic bombing operations against Japan, General Groves explains (in Now It Can Be Told: The Story of the Manhattan Project), American strategy was based upon the assumption that an invasion of the Japanese homeland was essential to ending the war in the Pacific:

Under the strategic concept approved by the Joint Chiefs in July of 1944, Kyushu was to be invaded on October 1, 1945, with the final assault on Tokyo following in December of that year. This plan was not dependent in any way upon Russian co-operation.

After the Yalta Conference, however, a debate sprang up over whether it would not be better to encircle Japan and defeat her by attrition than to defeat her by direct attack. Both General MacArthur and Admiral Nimitz, when asked for their opinion, voted for a direct assault.

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It was estimated that a force of 36 divisions—1,532,000 men in all—would be required for the final assault, and it was recognized that casualties would be heavy.

The Joint Chiefs of Staff approved the concept and on May 25 the directive for the Kyushu invasion was issued to General MacArthur, Admiral Nimitz and General Arnold. The target date for the invasion of Kyushu was now November 1, 1945.

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However, one very important question arose: should the United States delay any contemplated military action in the expectation that an effective atomic bomb would be produced as scheduled? To any experienced soldier it was obvious that, once an advantage had been gained over an enemy as dangerous as Japan, no respite should be given. If the bomb had been scheduled for delivery in early November, a few days after the scheduled date of the Kyushu invasion, I would have advised a delay in the landing operation. I expressed this point of view in conversations with Secretary Stimson and Harvey Bundy, but I also told them and General Marshall that I would consider it a serious mistake to postpone any feasible military operation in the expectation that the bomb would be ready as a substitute at some later date.

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Decisions of this nature must always be made by only one man, and, in this case, the burden fell upon President Truman.

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As far as I was concerned, his decision was one of noninterference—basically, a decision not to upset the existing plans.

When we first began to develop atomic energy, the United States was in no way committed to employ atomic weapons against any other power. With the activation of the Manhattan Project, however, the situation began to change. Our work was extremely costly, both in money and in its interference with the rest of the war effort. As time went on, and as we poured more and more money and effort into the project, the government became increasingly committed to the ultimate use of the bomb, and while it has often been said that we undertook development of this terrible weapon so that Hitler would not get it first, the fact remains that the original decision to make the project an all-out effort was based upon using it to end the war. As Mr. Stim-son succinctly put it, the Manhattan Project existed “to bring the war to a successful end more quickly than otherwise would be the case and thus to save American lives.”

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The first serious mention of the possibility that the atomic bomb might not be used came after V-E Day, when Under Secretary of War Patterson asked me whether the surrender in Europe might not alter our plans for dropping the bomb on Japan.

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At this same time a debate arose about how the bomb should be employed. Should we conduct a demonstration of its power for all the world to see, and then deliver an ultimatum to Japan, or should we use it without warning? It was always difficult for me to understand how anyone could ignore the importance of the effect on the Japanese people and their government of the overwhelming surprise of the bomb. To achieve surprise was one of the reasons we had tried so hard to maintain our security.

President Truman knew of these diverse and conflicting opinions. He must have engaged in some real soul-searching before reaching his final decision. In my opinion, his resolve to continue with the original plan will always stand as an act of unsurpassed courage and wisdom—courage because, for the first time in the history of the United States, the President personally determined the course of a major military strategical and tactical operation for which he could be considered directly responsible; and wisdom because history, if any thought is given to the value of American lives, has conclusively proven that his decision was correct.

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I had set as the governing factor that the targets chosen should be places the bombing of which would most adversely affect the will of the Japanese people to continue the war. Beyond that, they should be military in nature, consisting either of important headquarters or troop concentrations, or centers of production of military equipment and supplies. To enable us to assess accurately the effects of the bomb, the targets should not have been previously damaged by air raids. It was also desirable that the first target be of such size that the damage would be confined within it, so that we could more definitely determine the power of the bomb.

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One of the most difficult problems was attempting to estimate, or even guess, the probable explosive force of the weapon. An accurate guess was of vital importance because the closer we came to being right, the more effective the bomb would be. The optimum height of burst was entirely governed by the explosive force. If the altitude of burst we used was below or too high above this optimum, the area of effective damage would be reduced; and it was possible, if it was much too high, that all we would produce would be a spectacular pyrotechnical display which would do virtually no damage at all. We calculated that if the bomb was detonated at 40 per cent below optimum altitude or 14 per cent above, there would be a reduction of 25 per cent in the area of the severe damage.

At first, considerations of possible fallout and of direct radiation definitely favored a burst at a maximum altitude. I had always insisted that casualties resulting from direct radiation and fallout be held to a minimum. After the Alamogordo test, when it became apparent that the burst could be many hundreds of feet above the ground, I became less concerned about radioactive fallout from too low a burst.

For the present, however, since we did not know the size of the explosion, our plans had to be based on conservative detonation heights. For the Little Boy, it was estimated that the explosive force would have a TNT equivalent ranging from 5,000 to 15,000 tons. For this weapon, the corresponding desirable height of detonation would vary then from 1,550 feet to 2,400 feet. For the Fat Man, it was thought that the magnitude of the explosion would range from 700 to 5,000 tons. This would require detonating heights between 700 feet and 1,500 feet. We could only hope that we could tighten up these estimates considerably, particularly for the Fat Man, after testing the implosion bomb. This element of doubt meant that we had to have fuses for four different height settings. By then most of us in the project were thoroughly inured to such uncertainties. Indeed, three days later, on May 14, Oppenheimer informed me that he and von Neumann had concluded after a thorough discussion that the probable explosive power of the Fat Man was still uncertain, and that the views of the Target Committee should be amended accordingly. They estimated that the maximum altitude for which we should be prepared to set fuses was about twice the minimum, and even for the Little Boy the minimum and probable altitude was only two-thirds of the maximum.

It was agreed that visual bombing was so important from the standpoint of hitting the target that we should be prepared to await good weather. This was based on an estimate that there was only a 2 per cent chance that we would have to wait over two weeks.

The committee recommended that we have spotter aircraft over each of the three alternative targets so that the final target could be selected in the last hour of flight. In case the delivery plane should reach the target and find visual bombing to be impossible, they thought it should return to its base with the bomb. The drop should be made with radar only if the plane could not otherwise return. Radar and navigational developments should be followed closely so that these conclusions could be altered, if desirable.

We all recognized that the plan to use visual bombing, with the possible long delays entailed, required that the bomb be so designed that it could be held for at least three weeks in a state of readiness that would permit its being dispatched on twelve hours’ notice. This was not considered too great a problem at the time, and later we could ignore it as it became obvious that we would normally have at least forty-eight hours’ notice of possible suitable weather.

It was generally agreed that if a plane in good condition had to return to base with the bomb, it would probably be able to make a normal landing. Frequent practice landings had been made with dummy bombs, some of them filled with high explosives. The committee advised that special training in landing with dummy units should be given to all plane crews who were to carry the bomb.

If the bomb had to be jettisoned, extreme care would have to be exercised. Under no circumstances should it be jettisoned near American-held territory. Prior to actual take-off, definite instructions would have to be furnished the weaponeer to guide him in case of trouble. Careful calculations and the experience gained by the Air Force in England from missions involving bombs as large as two thousand pounds indicated that there was no reason to fear for the safety of the bombing plane if its flight were properly controlled. Discussion of the possible radiological effects did indicate, however, that it would be unwise for any aircraft to be closer than two and a half miles to the burst. To provide protection against blast effects, a distance of five miles was advisable. Also, no plane should be permitted to fly through the radioactive clouds.

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They had assumed that the atomic bomb would be handled like any other new weapon; that when it was ready for combat use it would be turned over to the commander in the field, and though he might be given a list of recommended targets, he would have complete freedom of action in every respect.

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I had always assumed that operations in the field would be closely controlled from Washington, probably by General Marshall himself, with Mr. Stimson fully aware of and approving the plans. Naturally I expected that the President also would share in the control, not so much by making original decisions as by approving or disapproving the plans made by the War Department. It was quite evident by now, however, that the operation would not be formally considered and acted upon by either the Joint Chiefs of Staff or the Combined Chiefs. One of the reasons for this was the need to maintain complete security. Equally important, though, was Admiral Leahy’s disbelief in the weapon and its hoped-for effectiveness; this would have made action by the Joint Chiefs quite difficult.

When I had visited him in his office six or seven months before to show him a status report on the project, he told me of his long experience with explosives in the Navy and emphasized his belief that nothing extraordinary would come out of our work. He reminded me that no weapon developed during a war had ever been decisive in that war. Then he went on to say he was sorry that I was involved in the project as it would have been much better for me to have had a different and more usual assignment.

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The cities that the Target Committee finally selected, and which I approved without exception, were:

Kokura Arsenal, one of the largest munitions plants in Japan, which was engaged in the manufacture of a wide variety of weapons and other defense materials. The arsenal covered an area of about four thousand by two thousand feet and was contiguous to railway yards, machine shops and electric power plants.

Hiroshima, a major port of embarkation for the Japanese Army and a convoy assembly point for their Navy. The city, in which the local Army headquarters, with some twenty-five thousand troops, was situated, was mainly concentrated on four islands. The railway yards, Army storage depots and port of embarkation lay along the eastern side of the city. A number of heavy industrial facilities were adjacent to the main metropolitan area.

Niigata, a port of growing importance on the Sea of Japan. It contained an aluminum reduction plant, and a very large ironworks, together with an important oil refinery and a tanker terminal.

Kyoto, an urban industrial area with a population of about one million inhabitants. It was the former capital of Japan, and many displaced persons and industries were moving into it as other areas were destroyed. Also, it was large enough to ensure that the damage from the bomb would run out within the city, which would give us a firm understanding of its destructive power.

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When I went over the list for him, he immediately objected to Kyoto and said he would not approve it. When I suggested that he might change his mind after he had read the description of Kyoto and our reasons for considering it to be a desirable target, he replied that he was sure that he would not.

The reason for his objection was that Kyoto was the ancient capital of Japan, a historical city, and one that was of great religious significance to the Japanese. He had visited it when he was Governor General of the Philippines and had been very much impressed by its ancient culture.

I pointed out that it had a population of over a million; that any city of that size in Japan must be involved in a tremendous amount of war work even if there were but few large factories; and that the Japanese economy was to a great extent dependent on small shops, which in time of war turned out tremendous quantities of military items. To reinforce my argument, I read from the description of Kyoto,, included in my report, which had now arrived. I pointed out also that Kyoto included 26,446,000 square feet of plant area that had been identified and 19,496,000 square feet of plant area as yet unidentified. The city’s peacetime industries had all been converted to war purposes and were producing, among other items, machine tools, precision ordnance and aircraft parts, radio fire control and gun direction equipment. The industrial district occupied an area of one by three miles in the total built-up area of two and one-half by four miles.

Mr. Stimson was not satisfied, and without further ado walked over to the door of General Marshall’s office and asked him to come in. Without telling him how he had got the report from me, the Secretary said that he disagreed with my recommendation of Kyoto as a target, and explained why. General Marshall read the target description of each of the four cities, but he did not express too positive an opinion, though he did not disagree with Mr. Stimson. It was my impression that he believed it did not make too much difference either way.

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In the course of our conversation he gradually developed the view that the decision should be governed by the historical position that the United States would occupy after the war. He felt very strongly that anything that would tend in any way to damage this position would be unfortunate.

On the other hand, I particularly wanted Kyoto as a target because, as I have said, it was large enough in area for us to gain complete knowledge of the effects of an atomic bomb. Hiroshima was not nearly so satisfactory in this respect. I also felt quite strongly, as had all the members of the Target Committee, that Kyoto was one of the most important military targets in Japan. Consequently, I continued on a number of occasions afterward to urge its inclusion, but Mr. Stimson was adamant.

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Nothing is more illustrative of the relationship between Secretary Stimson and me than this episode. Never once did he express the slightest displeasure or annoyance over my repeated recommendations that Kyoto be returned to the list of targets. Nor did I ever feel that he wanted me to remain silent, once I had learned his views, on a matter of such great importance. I believe the affair was also typical of his attitude toward other senior officers.

Events have certainly borne out the wisdom of Mr. Stimson’s decision. I think, however, he did not foresee that much of the criticism he so scrupulously sought to avoid would come from American citizens; certainly he never mentioned this possibility to me. After the sudden ending of the war I was very glad that I had been overruled and that, through Mr. Stimson’s wisdom, the number of Japanese casualties had been greatly reduced.

South Korea has received President Trump’s blessing to become the seventh country in the world operating nuclear-powered submarines, joining the United States, Russia, China, France, the United Kingdom and India:

South Korea could more effectively counter North Korean or Chinese moves in the waters around the Korean Peninsula; and that would free up the US Navy’s nuclear-powered attack subs to concentrate on patrols in hot spots like the South China Sea and the waters around Taiwan.

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Nuclear-powered submarines (SSNs) come with many advantages. They can stay submerged for long periods of time – essentially for years, if they can carry enough provisions for the crew – whereas most conventionally powered subs must surface for air to run diesel engines, which in turn charge their batteries for running at depth.

They are also generally faster than conventionally powered subs and are in many cases quieter.

Acquiring them has been a decades-long wish of the South Korean government.

But Seoul has faced a key roadblock: under a decades-old nuclear agreement with the US, it is not allowed to reprocess spent nuclear fuel, despite having the technology to do so.

[…]

“There are four-hundred foreign submarines in the world, of which roughly 75% reside in the Indo-Pacific region. One hundred and sixty of these submarines belong to China, Russia, and North Korea,” Davidson told the panel.

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As of July 1, 2025, a US Navy website shows it had 49 attack subs in its fleet, which must cover all the world’s oceans. About two-thirds of that fleet is available to “surge” in an emergency, the acting chief of naval operations said last April, but fewer subs are out on patrol during routine operations.

[…]

“The core issue in Trump’s post was the mention of the Philly shipyard,” said Kim Dong-yeob, South Korean military expert and a professor at the Institute for Far Eastern Studies at Kyungman University.

“What we wanted was not simply to possess nuclear-powered submarines but to secure related technologies and achieve industrial effects through domestic construction,” Kim told CNN.

“Building at the Philly shipyard means losing technology transfer. It is essentially no different from buying weapons built in the US.”

[…]

Shugart, however, questions South Korea’s wish: “It doesn’t make a lot of sense to me from an operational perspective.”

“The primary benefit to nuclear-powered (submarines) is mainly speed, being able to go fast for a long period of time and cross long distances at a rapid clip,” Shugart said.

But “South Korea and Japan are right there where the action is likely to be,” he continued, adding that SSNs could make sense if Seoul’s intention was to carry out aggressive anti-submarine warfare.

A potential South Korean nuclear-powered sub could also exacerbate an arms race in the region. North Korea called South Korea’s pursuit of SSNs “a strategic move for its own nuclear weaponization,” despite Seoul clarifying that the submarine would not carry nuclear weapons.