As our schedules became more definite in the latter part of 1944, we began to plan for the overseas operating base from which the B-29’s would take off for Japan. This meant that we had to inform the theater commanders and arrange for their assistance.
This need became more urgent when I began to receive reports that Admiral Nimitz was making inquiries about what the 509th Group was going to do in his theater. He had learned, somehow, that this unit would be operating in the Central Pacific, although he had never been told of its purpose. In order to avert what might develop into an embarrassing situation, I arranged, through Admiral Purnell, to have Commander Ashworth go to Guam to tell Nimitz about our plans and make certain of essential Navy co-operation. He went armed with a letter from Admiral King, stressing the importance of Ashworth’s message, and stating that only two officers were to be told of the purpose of our operations.
When Ashworth reported to Nimitz’ headquarters, he first saw Vice Admiral Charles H. McMorris, who insisted on receiving the message himself, saying that he was the alter ego of Nimitz and could take care of everything. Ashworth replied firmly that his message was for Nimitz and was to be delivered to him alone.
After hearing what Ashworth had to say, Nimitz picked McMorris as the other officer to be informed. Later, at Nimitz’ request, and with Admiral King’s consent, Captain Tom B. Hill, his gunnery officer, was brought into the picture and served as the immediate liaison officer with us throughout the operation.
Shortly before Ashworth left to see Nimitz, I had obtained General Marshall’s approval to tell Lieutenant General M. F. Harmon, the Deputy Commander of the 20th Air Force in the Pacific, and two of his staff about our plans, for by this time we felt certain that our bombing operations would be conducted from his area. Arnold arranged for this to be taken care of by General Norstad, who visited the Pacific in January of 1945. While he was there he also saw Brigadier General H. S. Hansell, Jr., Commanding General of the 21st Bomber Command, to which the 509th Group was to be assigned, but told him only that the 509th was a special organization. Unfortunately, soon after this, Harmon and the two staff officers disappeared in flight en route from Guam to Washington. Lieutenant General Barney McK. Giles took over the area command on May 4, and I was able to brief him thoroughly before he left Washington.
Norstad had returned from his trip to the Pacific convinced that Guam should be the 509th’s base of operations, primarily because of its fine deepwater harbor, with the additional attraction of its excellent maintenance facilities. Discussions with Ashworth and Tibbets, however, led me to believe that the one hundred miles of flying distance to the target that could be saved if we based on Tinian might well be an overriding consideration. The flight distance was extremely critical, because the plane carrying the bomb would be loaded to capacity and, in case of engine failure, might find itself in serious trouble.
Tibbets’ experience in the Caribbean training had indicated that we could expect to lose approximately five out of every forty engines in a flight comparable to the one we would have to make to and from the target. We decided with Norstad’s concurrence to use Tinian, regardless of the attractions of Guam; to provide for an intermediate emergency landing point, possibly on the Bonin or Volcano islands; and to make arrangements with the Navy to recover survivors and equipment in the event of a landing at sea.
The reasons for choosing Tinian instead of Guam were contained in Ashworth’s report, who in February, 1945, after seeing Nimitz, had investigated both sites:
Work on Tinian began at the end of February under the general supervision of the Navy. Before the first month had passed, it became apparent that we needed a personal representative on the island to ensure that there would be no delay in the preparations. For this I selected Colonel E. E. Kirkpatrick, who had just been assigned to my office. I had known him well when I had had charge of construction operations, and I had complete confidence in his ability to carry out smoothly any mission that involved dealing with other services.
In this instance his job was to see that all physical installations would be ready when they were needed. In some ways his assignment was an odd one in that it could be construed to indicate a lack of confidence in the support we would get from the authorities in the area. Actually, it was only another example of the extreme care we took to lessen the chances of failure. Nimitz told me after the war that it was the first time he had ever known the Army to send an ambassador to the Navy, adding that that was what he always considered Kirkpatrick to be. That thought had occurred to me, too, when I selected him. His two brothers were both graduates of the Naval Academy, a circumstance I felt might prove to be helpful. Actually it was not so great a factor in Kirkpatrick’s success as his ability to get along with people and at the same time to achieve his objectives.
I am sure that, but for Kirkpatrick’s presence, we would not have been ready, even with a wild last-minute rush, and that the delivery of the bomb either would have had to be postponed or made under much less favorable circumstances. A major source of delay would have been the congestion of Tinian’s unloading facilities. Another would have been the local authorities’ human tendency to take care of first things first, rather than to prepare for an uncertainty far in the future.
Before leaving for Tinian, Kirkpatrick had been instructed, as was usual, to prepare a code using names of states and cities to designate persons and things that would be repeatedly mentioned in messages. They would also be encoded in the usual secret code afterward, but this precaution was taken to protect security as the messages went through communication channels.
When his first message arrived in Washington it created considerable commotion in the message center for the code words were also the names of a number of important naval vessels known to be in the Pacific. Wild rumors spread rapidly. I immediately cabled him: “Destroy code. Send no messages. New code coming by courier.”
All Kirkpatrick’s messages came to me through Guam, except for his handwritten reports which he mailed directly as informal letters. Even in these, because of possible censorship, he had to be cautious. From their tone, however, I surmised that things might not be going so well as they should. Consequently, I cabled him that unless he felt it would be detrimental to the progress of the work he should return to Washington for a short conference. He came at once and explained the basic difficulty.
Because of the shipping jam, each vessel was required to wait its turn for unloading. This could mean a delay of as much as three months in the unloading of some of our vital equipment. It was a simple matter, through Purnell, to have Admiral King cable Nimitz that all of our material must be unloaded immediately upon its arrival at Tinian. This was quite upsetting to the normal operations on the island, but it was typical of the support that we unfailingly received from Admiral King, Admiral Purnell and the entire Navy at all times.
The very size of the military operations in the Guam area and the secrecy that shrouded our project made it impossible for the importance of our work to percolate down to all the various commanders and staffs with whom we became involved from time to time. However, as anyone familiar with military affairs will realize, orders signed Stimson or Marshall or King or Nimitz carried unprecedented weight during the war years. An example of that basic fact of military life was what happened when on one occasion Kirkpatrick needed more cement than he had. There was none on Tinian, but he had learned of some on another island. The naval officer who controlled it refused, as was quite natural, to turn it over to him unless he explained why he needed it. This, of course, Kirkpatrick could not do, but he saw Captain Hill, who sent a peremptory order over Nimitz’ signature to the naval officer to turn over all the cement Kirkpatrick wanted at once and to ask no questions about need or purpose for there was no intention of telling him.
At the time we chose Tinian as our base, both Iwo Jima and Okinawa were still held by the Japanese. Neither island had been considered suitable for our purposes, in any event, for they were too close to the Japanese homeland for the safety of our assembly operations. In the spring of 1945, however, we decided to have an emergency bomb-handling facility installed on Iwo Jima, so that if the plane carrying the bomb had aircraft trouble, the bomb could be shifted to another plane. On April 6, the necessary instructions were issued by Admiral Nimitz’ headquarters, with highest priority assigned to the work.
Kirkpatrick visited Iwo Jima in the middle of April and showed a copy of the order to the local authorities. It was agreed then that the job was to be completed by July 1. But when an officer courier delivered some MED equipment there on July 1, he found and reported that little work had been done and that the island engineer was now planning on completion on July 15. Kirkpatrick investigated promptly and found conditions even worse than reported. This time he was assured that August 1 would be the completion date. He thereupon took the matter up with Captain Hill and the situation was corrected just in time. This was another instance where having a responsible officer in the area checking on every detail paid off, for if Kirkpatrick had not been there, I doubt if the handling facilities at Iwo Jima would be ready yet.
I had begun to think about the make-up of the field crews for Tinian as early as June of 1944. These would be the men who would carry out the last-stage experiments and tests and be responsible for the final assembly of the bomb. At the time, I felt it would be wise to delay their selection, since the skills and experience needed might change with the design of the bomb, and there seemed to be so many people anxious to volunteer. Consequently, the thirty-seven-man team of twelve civilians, seventeen Army enlisted men, seven Naval officers and one Army officer was not chosen until early May, 1945.1
This group of specialists from Los Alamos formed part of what was known as the First Technical Service Detachment. Each civilian was required to wear a uniform and received an assimilated Army rank. Two of the scientists were commissioned as reserve officers in recognition of the duties and responsibilities they would have in connection with the bomb assembly. After they had been appointed, we found that this was not a happy solution for one of them so we placed him in an inactive status and sent him over as a civilian.
The job of the Los Alamos group on Tinian was to provide and test bomb components and also to supervise and inspect the actual assembly of the bombs. They were to inspect the bomb prior to takeoff, test the completed unit, and co-ordinate the various project activities on the island. They were not responsible for providing any advice concerning the use of the weapon.
There was considerable furor over the exchange of information between Tinian and Los Alamos, but, though there were difficulties at each end, the loudest complaints came from Los Alamos, where the people did not receive all the information that they thought they would like to have. The reason for this was simply that very little information was being sent. Direct communications between Los Alamos and Tinian were not permitted for security reasons and what messages did pass had to be relayed through Washington, which required the use of a fairly elaborate table of codes which had been prepared by Alberta. To get around this difficulty and particularly to assure the Los Alamos scientific people that the information to which they were entitled was not being held back, we arranged for Dr. J. H. Manley to come in from the laboratory to Washington. He remained there to pass on information as it was received from Tinian and Los Alamos. In the process he had to rewrite all messages to eliminate any chance of our codes being broken.
The 509th Group had begun to stage out of the United States at the end of April. Approximately eight hundred of its members sailed from Seattle in the early part of May. The advance air echelon reached Tinian around the twentieth, and by the middle of July, all elements of the group were present on the island. The shipment of their equipment progressed smoothly; and the men quickly settled down to the routine of life in the field and began the last phase of their training.
Prior to shipment overseas, all Army Air units were customarily inspected by an outside team of officers to make certain that all equipment was in perfect order. For the 509th, this inspection was well along toward completion when the Second Air Force, which exercised administrative control over the 509th, learned of it and peremptorily ordered it discontinued with the comment, “They can’t inspect the 509th because they are ignorant of the mission.”
Upon its arrival in the theater, the 509th Group was placed under the direct operational control of the 21st Bomber Command (now under Major General Curtis LeMay) of the 20th Air Force. When LeMay had come to Washington in June, we had met to discuss the delivery of the bomb. General Farrell, who was devoting most of his attention to planning the actual operation, was also present.
This was my first meeting with LeMay and I was highly impressed with him. It was very evident that he was a man of outstanding ability. Our discussion lasted about an hour, and we parted with everything understood and with complete confidence in each other. This feeling lasted throughout the operation and into the years since then.
I explained to him the anticipated outcome of our work, describing the probable power of the bombs, their expected delivery dates and probable production rates, and said that we fully expected to drop each bomb as soon as it was ready. I also went into the general organization and state of training of the 509th Group; the responsibilities of the supporting groups from Los Alamos; the factors governing the altitude from which the bomb would have to be dropped, which was approximately the maximum altitude of the B-29; the approximate weights of the two types of bomb; the targets that we had selected; and the type of instructions that would be issued to the field. I made it perfectly clear that the conduct of the operation would be entirely under his control, subject, of course, to any limitations that might be placed upon him by his instructions. Finally, I explained the roles of the two weaponeers, Parsons and Ashworth—the men who would actually arm the bomb—giving him a resume of their particular qualifications.
LeMay asked a few very pertinent questions, and then announced that he would want to carry out the bombing operation using a single unescorted plane. In explaining his reasons for preferring this radical tactic, he pointed out that the Japanese were unlikely to pay any serious attention to a single plane flying at a high altitude, and would probably assume that it was on either a reconnaissance or a weather mission. I replied that I thought his plan was sound, but that this phase of the operation came under his responsibility. I added, however, that some arrangement should be made for the necessary observation planes to be present in the general area at the time the bomb was dropped.
After their arrival on Tinian all combat crews went through the seven days of regular schooling required in the theater before combat flying could be undertaken. During the next twenty days they flew practice missions over various targets, such as Truk.
Because they had been modified to carry the atomic bomb, the B-29’s of the 509th Group could not easily carry standard conventional bombs. They could, however, deliver bombs having the same shape as the Fat Man, and such a bomb had been developed and produced to provide training and experience to the crews. Known as the Pumpkin, this bomb contained 5,500 pounds of explosives, and was designed for blast effect only, with a proximity fuse that would permit its use for an air burst. Although it was primarily a training device, we had always recognized that it could have tactical uses; now as part of the group’s security cover, we let it leak out on Tinian that its mission was the delivery of Pumpkins in battle. We also hoped that analysis of the results obtained by the use of the Pumpkins might help us to refine the ballistic data for the real bomb.
The Pumpkins began to arrive at the end of June. Reaction to these bombs were mixed. The members of the 509th who, with a few exceptions, still did not know the real reason for their training, were somewhat disappointed that they had spent so much time in practicing to deliver this fairly modest weapon. On the other hand, some members of the other Air Force units based on Tinian, who likewise did not know what the 509th’s real purpose was, became quite enthusiastic about the effectiveness of the Pumpkin’s air bursts over enemy targets and set up a clamor to have more of them made available to their theater.
To familiarize the plane crews with the general areas of the targets and to ensure more certain navigation and target recognition, the cities selected for the Pumpkin missions were in the general vicinities of, but outside, the atomic targets. The bombings were carried out at the same high altitudes, and daylight visual bombing was specified; however, radar could be used if visual aiming proved impossible.
The flights were planned to pass over Iwo Jima in both directions. The altitudes to be used depended on the weather, with a limitation of ten thousand feet or less going to the target, and eighteen thousand feet or more returning, so that the local defenses would not be unnecessarily alerted. All planes were required to carry a maximum load of fuel.
Every effort was taken to make these flights as much like the main job as possible. For this, wide deviations from usual bombing techniques would be necessary because of the terrific power of the explosion and the high air burst that would occur instead of the usual impact or delayed explosion.
As I have explained, a high air burst was necessary for maximum results. It was also dictated by our desire to eliminate, if possible, or in any case to decrease, residual radioactivity on the ground below the burst; to decrease to a negligible degree any harmful fallout downwind; and to diminish to a minimum serious radioactive injuries to the population in the bombed area. We felt that the high burst would confine casualties for the most part to nonradioactive injuries; namely, those due directly and indirectly to the force of the unprecedented explosion.
To be well removed from the point of burst, the bombing plane would have to maneuver as no heavy bomber had ever had to maneuver before. As soon as the bomb was “away,” the plane was to make a sharp diving turn to get as far as possible from the point of explosion. This was one of the reasons why the run was made at the then unprecedented altitude of some thirty thousand feet. The high altitude also greatly reduced the danger of gunfire from enemy airplanes, permitting the removal of the fuselage turrets and all other armament except for the tail guns. This weight reduction appreciably increased the plane’s range and the height at which it could fly.
Studies made at Los Alamos had determined that with a bomb of twenty thousand tons of TNT equivalent, a B-29 plane ten miles away from the burst would be safe from destruction by a factor of two. Under these conditions, the aircraft, which had been designed to withstand a force of four times gravity, would be subjected to a force equivalent to no more than two times gravity. It was calculated that by making a sharp diving turn, the sharpest possible consistent with safety, the B-29 could reach a point at least ten miles from the burst by the time the bomb exploded.
In late June, as the forces under General MacArthur and Admiral Nimitz approached within bombing range of the Japanese homeland, we suddenly realized that they had not been told about the ban on certain cities, for at the time it was imposed they had been too far away to make it necessary. This concern was soon removed, however, for when we brought the matter to the attention of the Joint Chiefs, they hastily reserved our targets from all air attack.
1 The key positions were manned as follows: In charge—Parsons; Scientific and Technical Deputy—Ramsey; Operations Officer and military alternate to Parsons—Ashworth; Fat Man Assembly Team—Warner; Little Boy Assembly Team—Birch; Fusing Team—Coll; Electrical Detonator Team—Lieutenant Commander Stevenson (a reserve officer and a scientist); Pit Team—Morrison and Baker; Observation Team—Alvarez and Waldman; Aircraft Ordnance Team—Dike. Special Consultants included Serber, Penney, and Captain Nolan, an Army medical officer.