The Manhattan Project
PART 2  |  QUEST FOR THE ATOM
1942 - 1945

Quest for the Atom | Introduction:

After the attack on Pearl Harbor, an effort to develop an atomic bomb by the United States was commenced at three secret facilities: Los Alamos in New Mexico, the Hanford Reservation in Washington State, and Oak Ridge Tennessee.  Code-named the Manhattan Project, it became the largest single industrial endeavor in the history of the world. For three years, hundreds of eminent scientists lived with their families in secret isolation and worked on the project under crude working and living conditions. ATOM DAYS takes viewers back to these remote and mysterious facilities and shows viewers how these scientists accomplished in practice what previously was only theorized. On July 16, 1945 at a test site named Trinity in Alamogordo, New Mexico, the first atomic explosive device was tested. By the time of the test, Nazi Germany had been defeated in Europe and the United States was preparing to invade mainland Japan in the Pacific.  The Japanese Navy and Air Forces were already nearly completely destroyed but Japan refused to surrender.  Faced with the prospect of an allied invasion that would have cost hundreds of thousands of lives, President Truman ordered the atom bomb to be used against Japan. On August 6th, the world’s first uranium atomic bomb called “Little Boy” was dropped on the city of Hiroshima resulting in an explosion the equivalent to 12,500 tons of TNT. Approximately 66,000 people were killed from the blast and many of the 69,000 thousand people injured that day, later died from radiation released from the weapon. ATOM DAYS takes viewers back to Hiroshima that fateful day through first hand accounts told by the survivors of the world’s first atom bomb attack.

1942 | Vannevar Bush

Vannevar Bush, director of the Office of Scientific Research and Development (OSRD), wrote to President Franklin Delano Roosevelt on March 29th, 1942. The report that accompanied the letter stated that five to ten pounds of “active material” would explode with a force of 200 tons of TNT. The report went on to describe the various methods for producing an atomic bomb and the current estimated costs and schedules for its completion. Moreover, it echoed previous warnings about a possible German program: “ present opinion indicates that successful use is possible, and that this would be very important and might be determining in the war effort. It is also true that if the enemy arrived at results first it would be an exceedingly serious matter”. FDR responded two days later. “I think the whole thing should be pushed not only in regards to development but also with due regard to time. This is very much of the essence.”
(The Making of the Atomic Bomb by Richard Rhodes, pp. 402-406)

1942 | Arthur H. Compton

Arthur H. Compton, under Bush’s direction, held a meeting on June 27th, 1942 with the various research project leaders working under the Uranium Committee of the OSRD. He opened the meeting with the directive that the U.S. was now committed to building an atomic weapon for use under the direction of the U.S. Army. He emphasized secrecy and made it clear that the scientists would be working with an industrial contractor and may have to be commissioned as officers in the military. Most of the scientists present objected and many of those who had been involved in early research for the committee considered not pursuing an atomic weapon under such authoritative control. Soon after, a theoretical physicist named Robert Oppenheimer, who up to that time had only played a small advisory role, called a meeting of theoreticians to begin considering the design for an actual bomb. Oppenheimer was a physicist at Berkeley and had been originally recruited into the project by Ernest Lawrence due to his unique problem solving talents. Oppenheimer was also a socialist by ideology; a fact that nearly excluded him from the project. Nevertheless, he was well known and respected by all the other scientists involved. He was also keenly aware of the tremendous scientific and engineering obstacles of creating a working bomb. As a result, he was encouraged to recruit a team of minds that could accomplish in practice what was previously only theory. Among others, these included Hans Bethe, the 36-year-old top Cornell physicist and Edward Teller. Before work had even begun on building the fission bomb, Teller proposed the possibility of using it to ignite deuterium to create a fusion atomic reaction of hydrogen atoms that might release a thousand times more energy than splitting uranium or plutonium atoms. The idea became known as the “Super”. Later the “Super” became a reality in the form of the hydrogen bomb. While it was an area of great interest among the theoreticians, the ‘Super” would have to wait for the creation of its trigger - the fission atom bomb.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 412-418)

1942 | Leslie Richard Groves

Leslie Richard Groves was a colonel of the Army Corps of Engineers and had just completed the assignment of building the world’s largest building; the Pentagon. He was hoping to be reassigned overseas to get out of Washington D.C. Soon after, he received the most important assignment of his life on September 17th, 1942 in a hallway:

[General] “Brehon B. Somerville met me in a corridor”…”about that duty overseas…you can forget it…the Secretary of War has selected you for a very important assignment.”
“Where?”
“In Washington.”
“I don’t want to stay in Washington.”
“If you do the job right, it will win the war.”
“Oh.”

Groves was called by one of his colleagues and subordinates “The biggest son-of-a-bitch I ever met” and rightly so. He was big (over 250 pounds and growing) and he was as tough as they came. He was a man who got things done – on time – and on budget. Groves began his assignment like any Army commander would, first by securing his supplies – in this case uranium. In late September he approved a previous directive to acquire 52,000 acres of land along the Clinch River in the Tennessee Valley – Site X; which became known as the Clinton Engineering Works at Oak Ridge Tennessee. Over the next three years it became a vast complex where fuel for the world’s first uranium bomb would be processed by various methods. The following week Groves was promoted to Brigadier General.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 423-427)

1942 | Robert Oppenheimer

Robert Oppenheimer was only thirty-eight years old in 1942 but had already done some of his most important theoretical work in physics. In early October of 1942 he met with Leslie groves for the first time and proposed the need for a central laboratory to move the atomic bomb project forward and eliminate the various compartmental experiments that had characterized the program so far. Groves became impressed with Oppenheimer and although he had no experience leading large groups of people and had only played a small role thus far, he selected him to become the Director of the project. Despite his leftist political orientation, He and Groves met with Vannevar Bush in Washington on October 19th and Oppenheimer was officially appointed. His first assignment was to find a suitable location for the new Laboratory he had proposed, and to recruit as many scientists into the program as possible.

Site Y needed to be located in isolation in a good climate and have access to an adequate supply of water and a labor force. After considerable scouting the site of an old Boys School in the New Mexico desert was selected. The school was called Los Alamos and was located on a 7200-foot mesa. It fit most of the criteria and had a good climate that would allow for outdoors experimentation on a year round basis. Groves approved the site based on an Army Corps of Engineers appraisal in Late November. The school and land was purchased for $440,000 and the Manhattan Project had its experimental laboratory site.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 446-451)

1942 | Uranium Pile Experiment

Enrico Fermi and Leo Szilard were now in the final planning stages for a full-scale graphite and uranium “Pile” experiment at the Metallurgical Laboratory or "Met Lab" of the University of Chicago. It was built under the stands of Stagg Field in a squash court. The pile took up almost the entire space and was essentially a much larger version of the previous pile experiments. Housed in a wooden casing, were 56 alternating layers of graphite surrounding purified uranium metal spheres incased in bricks. It had ten control rods made of cadmium sheets nailed to wood strips that could pass through the layers of the pile. The rods were the safety barriers that separated the fissionable materials and kept the pile from reacting. On the morning of Dec 2, the Met Lab team began the experiment. Gradually over the course of several hours the rods were removed. At 3:53 pm, the pile went critical proving that a controllable atomic fission reaction was possible on a large scale. The worlds first Nuclear Reactor was born. After a brief celebration with a bottle of Italian wine that all the present scientists signed, Leo Szilard shook hands with Fermi and told him that the experiment would go down as a black day for the history of mankind.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 435-442)

The successful chain reaction in Chicago proved plutonium could be produced on a large scale. Twelve days after the experiment, Groves was looking for a suitable site for plutonium production. The Tennessee site was ruled out due to its relative close proximity to the city of Knoxville. The word “meltdown” did not yet exist, but Groves and his scientists knew there would be radioactive hazards if an atomic reactor got out of control and exploded. They also did not want to risk damaging the gaseous diffusion plants at the Clinton Works. The site needed access to plenty of electricity and water for the cooling systems and for safety it needed to be remote. The area selected in late 1942 was contained in a 500,000-acre preserve in Washington State along the Columbia River. The Union Pacific Railroad crossed over one corner of the parcel and it had rudimentary roads leading to a sparse riverside village named Hanford. It had a population of roughly 100 persons. The huge tract of land was purchased in January of 1943 for 5.1 million dollars and given the name the Hanford Engineering Works. Later, it became known as the Hanford Reservation due to its remote location.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 496-497)

In 1943, General Groves recruited the University of California to be the contractor for the Los Alamos Lab and construction of inexpensive barracks style buildings commenced. The lab was not intended to outlast the war years and had very few amenities. There were no sidewalks or paved roads and only wood burning stoves for heat. While Oppenheimer loved the ruggedness of the planned facility (as he had spent much time in the area as a youth) many of his future colleagues despised the idea. Leo Szilard, who was accustomed to an urban life-style remarked “Nobody could think strait in a place like that…Everyone who goes there will go crazy.” Oppenheimer traveled around the county to recruit every scientist he could to work on the project. At first, even many of his closest colleagues were less than interested in working for the U.S. Army, as commissioned officers, in a remote location for an extended period of time. After some debate, Groves allowed the laboratory to be operated by a civilian administration until such time as large-scale military experiments proceeded. Armed with this, Oppenheimer was able to convince most of the great minds available to work on the project.

1943 | Leo Szilard

Leo Szilard opposed the military take over of the atomic bomb project from the start and opposed the corporate takeover of the nuclear fission program he and Fermi had essentially invented at the Met Lab in Chicago. He was uncooperative with Dupont Engineers who arrived at the Met Lab in Chicago to take control of the Pile design that would later be enlarged into an industrial version at Hanford. Szilard did not agree with the Army compartmentalization of the project and immediately began breaking the rules by ignoring regulations that forbade open discussion across different lines of research. Gen. Groves was suspicious of Szilard’s Hungarian heritage from the beginning, and described him as “ The kind of man any employer would have fired as a troublemaker.” Groves officially reprimanded Szilard and threatened to remove him from the project. Szilard ignored him and consequently Groves wrote a letter to the U.S. attorney General characterizing Szilard as an enemy alien and recommended he be interned for the duration of the war. In his defense, Szilard presented a body of documentation that demonstrated his participation in bringing the news of nuclear fission to President Roosevelt along with Einstein as well as his efforts to enforce voluntary secrecy among the key scientists involved in the research. He was also defended by most of the physicists now involved in the project. Groves backed off but put Szilard under surveillance. Szilard later tried to use his legal rights of the early patents he had filed on atomic fission to wrestle some control of the project from the military. In response, he was informed that the government had the rights to his inventions so long as he was employed in the project. Szilard then refused to renew his contract. After a considerable legal conflict, Vannevar Bush corresponded with Szilard, listened to his concerns and provided him some reassurances. Groves and Szilard came to a truce and the Army paid Szilard reimbursement of back wages, lawyer fees and provided him a commission equal to the other high-ranking scientists working on the project. Ten years after the war, Szilard and Fermi won a joint patent for the invention of the nuclear reactor.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 501-509)

1943 | Heinrich Heisenberg

Heinrich Heisenberg was continuing his progress towards an atom bomb aided by his access to uranium mines captured in Europe by the Nazi war machine. British intelligence was now well aware of this and began contemplating how to sabotage his efforts. He was too well guarded to consider an assassination attempt, and even if it was possible, the program might still succeed. There was only one weakness to the Nazi atomic bomb program. Heisenberg had chosen heavy water as the primary method to slow neutrons in his experiments to bombard uranium atoms to create a sustained chain reaction. He had also made the decision to acquire his heavy water supply from a single source in Norway now under German occupation. Instead of building a heavy water manufacturing facility in Germany close to his laboratories in Leipzig or Berlin, he made the fateful decision to modify and use the plant in Norway exclusively. The Norwegian plant was located in a secluded, almost inaccessible location perched high in a mountainous ravine and had a powerful energy supply of waterfall generators. It was originally built as a research facility that only produced small quantities of heavy water as a by-product of its research operations. After occupying Norway, the Nazis quickly increased production of heavy water by forcing the plant engineers to work exclusively on on production Heisenberg’s atomic bomb program in 24-hour-a-day shifts. There was only a small garrison of German troops at the factory as it was considered too difficult a location to assault had a single suspension bridge providing access to the complex. Two British attempts to sabotage the plant by glider ended in crashes. Then in mid February, nine commandos from the Norwegian underground changed the course of history. After waiting the entire winter living in tents, the nine native volunteers cross county skied for over a week to the complex and scaled the steep ravine below the facility. They entered the complex at about 1:00 AM, and with the passive assistance of the plants workers, planted explosives in the heavy water separation collection cells. They quietly made there way out of the complex and down the gorge. A few small muffled thuds in the middle of the night ended the German atomic bomb program. The Germans later repaired the facility but the British sank the last subsequent shipment of heavy water as it was being transported on rail cars over a deep river by ferry. Historians speculate that Heisenberg’s efforts were also limited by his use of thin sheets of uranium oxide layered with beryllium that could not have achieve a full chain reaction. After the war, Heisenberg told his British contemporaries that he intentionally derailed the German atomic bomb project due to his fear that Hitler would use it to attack civilian targets. His statements have never been fully validated.
(E = mc2: A Biography of the World's Most Famous Equation by David Bodanis, pp. 135-142)

In Japan, efforts were also being made to exploit the use of atomic physics for war purposes. Since 1941, both the Japanese navy and army had individually proposed the exploitation of such research; which was by then widely known among scientific circles. By 1942, the navy had already been committed to explore nuclear power as a means of propulsion for warships. The committee overseeing the project was also convinced that the United States was probably working on an atomic bomb program by that time. While they agreed that an atomic bomb was possible, it was concluded that neither Japan nor any other major power involved in the war had the sufficient industrial capacities for developing a practical weapon in time to be used decisively during World War II. After considerable debate, the committee decided it would be more advantageous to dedicate research efforts to in more practical areas of military science such as radar technology. Another branch of the Japanese Navy, the Fleet Administration, had also pursued the technology for the development of an atomic weapon. However, the defeat of the Japanese fleet by the U.S. Navy at the Battle of Midway in 1942 resulted in the loss of Japans aircraft carriers and many of their best warships. The Japanese Navy was forced to move into a defensive posture in the Pacific war and did not have the economic resources to continue to pursue an atomic weapons program effectively.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 457-459)

1943 | Los Alamos

Robert Oppenheimer assembled his preliminary staff at Los Alamos in March of 1943. They began with a series of lectures by the senior scientists who had already done work on the atomic weapon program. These included the work of Hans Bethe, Edward Teller and Emilio Segre. Bethe was a Cornell physicist and theoretician that had identified the thermonuclear reactions in stars. Teller had also been researching thermonuclear reactions including those that involved deuterium and tritium. This research would later lead to the development of the Hydrogen Bomb. Emilio Segre had participated in the discovery of slow neutrons and plutonium-239. The purpose of these initial orientations was to share acuminated knowledge and set forth a plan for the development of a practical military weapon in the form of a bomb from which energy could be released by a fast neutron chain reaction. They estimated that the core of the first atom bomb would either be a sphere of U235 weighing 33 pounds or sphere of Pu239 at 11 pounds. The goal was to get as much energy release out of the chain reaction as possible. Both fuel reactions would rely heavily on a tamper encasement to slow the chain reaction so it would not expand too quickly and fizzle out before enough reactions could occur so as to create a full-scale atomic explosion. Properly tamping the “Gadget” (as the weapon design came to be known) posed a variety of challenges. Equally difficult would be the design of an effective detonator for the device. It was agreed that firing a piece of fissionable material into a target mass at high velocity from a gun barrel would be the simplest approach. However if the masses went critical before they had completely mated then the weapon would pre-detonate and only explode with a fraction of its potential force. Of the various designs discussed the most favored was to fire a cylindrical male bullet of fissionable material down a gun barrel into a mated female sphere of tamper and core welded to the gun’s muzzle. They estimated this would require a projectile velocity of roughly 3000 feet per second. The most powerful naval guns in the U.S. could obtain such velocities but they weighed over five tons and were 21 feet long; which would be far to large and heavy for a practical bomb design. Later it was realized that since the gun would only have to fire once this weight could be drastically reduced. With these plans in mind the Los Alamos scientists began to formulate methods for reducing enriched uranium and plutonium into metal and to develop the initiator for starting the chain reaction.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 459-463)

1943 | Seth Neddermeyer

Seth Neddermeyer, A young Los Alamos scientist, conceived a totally different configuration for detonation. The concept, known as implosion, came out of early lectures to the team by military ordinance experts. Neddermeyer proposed using a spherical layer of explosives around a tamper and the bomb core that would be detonated simultaneously causing it to explode inward and squeeze a hollow core of fissionable material to collapse into a chain reaction. Oppenheimer and many of the other scientists initially resisted the idea because they felt that it would be impossible to coordinate the explosions precisely enough to create the even pressure necessary to cause the chain reaction. Later though, Oppenheimer reconsidered and assigned Neddermeyer as group leader to the ordinance division for implosion experimentation. It was a fateful decision, as implosion would prove to be the only method that could detonate plutonium.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 461-467)

Total War was now raging across all of Europe and strategic bombing of military targets by the British Royal Air Force had had only limited success against the German war machine. Soviet Russia was fighting a brutal ground war on the eastern front and Joseph Stalin was demanding that Britain and the U.S. open a second front in the West. However, neither ally was yet prepared or strong enough to launch an invasion of Europe. Fearing that Stalin might sue for a separate peace with Hitler, due to the millions of Russian lives being lost on the ground, the allies had stepped up it’s bombing campaigns in Europe to relieve pressure on the Eastern Front. Due to terrible bomber loses against German fighter aircraft the RAF had switched to strategic night bombing which subsequent studies proved were inaccurate and had little effect on Germanys ability to wage war. This resulted in a change of bombing strategies that were new to the rules of war. Rather than targeting military or industrial targets it was decided that the area bombing of civilian populations would be more effective. This strategy was designed to reduce the morale of the enemy, as Hitler had tried with the terror bombing of London, and attempt to kill the workers supporting the enemy war machine. By this time more advance incendiary bombs had been developed and could now be used to bomb German cities. On May 27 1943, as the scientists at Los Alamos began their work on the atomic bomb, the Germany city of Hamburg was attacked with wave after wave of British and American bombers. The city was engulfed in a firestorm and reduced to ashes. Over 45,000 German people including the elderly, women and children were burned alive. Later the fire bombing of the city of Dresden resulted in between 24,000 and 40,000 civilian deaths.

(The Making of the Atomic Bomb by Richard Rhodes, pp. 472-474)
(Dresden by Frederick Taylor, pg. 508)

1943 | Bombing of Hamburg

The bombing of Hamburg was the result of a new Allied doctrine to force the total surrender of Japan and Germany. As horrible as it was, the atrocities that were being perpetrated by the Axis powers were far worse. On the eastern front over two million captured Russian soldiers were starved to death in German prison camps. At the same time, genocide in the form of Hitler’s “Final Solution” was being carried out against the European Jewish population. Several million people would be exterminated before the war's end. On the other side of the globe Japan was engaged in it’s own horrific war policies and practiced genocide against occupied China. The rape of Nan king and The Bataan death march are two notable examples. Humanity had begun to walk down the path of self-destruction. Allied leaders now believed that only the total defeat of the Axis powers would bring an end to World War II, even if that meant the destruction of entire cities and civilian populations.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 482-487)

1943 | Oak Ridge Tennessee

The Clinton Works at Oak Ridge Tennessee were by now being developed into one of the largest industrial complexes in the history of the world. Due to the fevered pace, the construction of many of its facilities began before the engineers knew exactly what they were building. There were two planned industrial scale methods of extracting bomb grade fuel from uranium ore at the complex. The first was the model demonstrated by the experiments of Earnest Lawrence by use of cyclotrons in extracting highly enriched uranium U235 through electromagnetic isotope separation. This model was extrapolated into large-scale systems called racetracks that utilized enormous magnetic mechanisms in the form of oval shaped tracks to extract the enriched uranium one atom at a time. The second method being developed was the gaseous barrier diffusion process. This involved the construction of enormous networks of equipment similar to petroleum refineries to carry out the process on an industrial scale based on experimental work being done at Columbia University in New York City. The basic approach was to pass raw uranium transmuted to a gaseous form though a series of porous barriers. The lighter molecules of u235 would pass through faster than the heavier molecules of u238 thus separating out the enriched uranium. The heart of the process depended on the barrier, which was comprised of a porous metal membrane with millions of submicroscopic openings. Since there was so little variation of the molecular state of the two gases, there had to be thousands of successive stages of the process for it to be effective. As a result, the Clinton Works grew into an enormous complex and employed tens of thousands of workers.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 490-495)

1943 | Hanford Reservation

The Dupont Corporation was commissioned to build the enriched plutonium producing facilities at the Hanford Reservation as an alternate fuel for an atomic weapon. It would be the single largest construction project the company had ever attempted. Three riverside piles, which became known as reactors, and three supporting chemical separation plants were to be built within a year. The separation plants were constructed ten miles away from the reactors for safety. The buildings would each be 800 feet long and 80 feet tall – each nearly a large as the Queen Mary. The reactors were planned at six-mile intervals along the Columbia River. In August of 1943 construction commenced on the reactors. According to official estimates 390 tons of structural steel, 17, 400 cubic yards of poured concrete, 50,000 concrete blocks and 71,000 concrete bricks were used. After considerable debate, water was chosen over helium as the cooling method for the piles. Eugene Wigner had design a practical prototype pile that proved water could provide suitable cooling for the radioactive piles that would each generate hundreds of thousands of kilowatts of heat. Water from the river would be circulated around the canned uranium slugs in the piles at a rate of 75,000 gallons per minute. Once the slugs had undergone fission reaction long enough to produce the plutonium isotope (about 1 atom out of every 4000) they would be pushed out of the back of the pile into deep pools of purified water. Once they had dissipated their most energetic radioactivity they would be transferred to the chemical separation plants to extract the bomb grade plutonium.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 499-501, 603-604)

1943 | The Gadget

At Los Alamos, work towards producing the “gadget” was proceeding. Captain William “Deke” Parsons, a naval officer, was appointed to direct the ordinance division at the lab and begin work on the delivery system for a bomb. His first task was to explore the possibility of the gun design. Based on previous studies he determined that the weapon would need to be at least 17 feet long to achieve a 3000-foot per second velocity and could weigh no more than a ton to be carried by aircraft; which meant it would have to be machined from the best grade alloy steel available. Parson initiated naval engineers to begin the design. At that size, the only aircraft available to the allies for delivery would be the British Lancaster or the new untested B-29 Super Fortress. Even so, both aircraft would require significant modifications and customization to deliver the payload. U.S. military officials pushed for the B-29 even though it was only in early experimental testing stages and had crashed during initial test flights. On August 13th of 1943 the first test fights of a dummy gadget took place on a scale of 14/23 of the estimated size of the weapon. The test was a complete failure as the bomb dropped in a flat spin completely missing the target.

Nevertheless, it served to teach the ordinance division valuable lessons about the aerodynamics of the odd shaped ordinance. Subsequent modifications to the bomb design and further tests proved more successful. During this time implosion design experiments by Seth Neddermeyer were also failing to produce desired results. Cylindrical models were being tested at first because of their simplified mathematical calculations. Limited amounts of explosives were used so as to have collectable remains to examine. The initial results became known as the “beer can experiments” referring to the possibility of exploding a beer can inwards without splattering the beer all over the place. Despite the failures most of the project leaders felt that the implosion design held several advantages over the gun design. A casing of high explosives wrapped around a tamper and atomic core, would be only about 5 feet in diameter and 9 feet long and thus made a practical design for a deliverable bomb.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 479-481)

1943 | Emilio Segre

Emilio Segre made an important discovery in December of 1943. Based on experiments of measuring the fission rates of U235 in a lab 7500 feet above sea level, he found that if stray cosmic ray neutrons (that naturally occur in the upper atmosphere) were shielded out, a U235 bomb core could be purified to a lesser degree. This meant that the gun mechanism for detonating the bomb could be significantly shorter and lighter. With this new information, the ordinance division determined that the new design would only have to be six feet long rather than seventeen feet long and would weigh less than 10,000 pounds. This new design became known as “Little Boy” and the previous “Thin Man” version was abandoned. A B-29 aircraft could deliver the “Little Boy” bomb with very little modification. This dramatically reduced the time it would take to develop and deploy a practical weapon based on the new gun design.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 539-540)

1944 | Edward Teller

In 1944, Edward Teller was pressing for the development of the “Super”, a thermonuclear bomb that could release a thousand times more energy than the atomic weapon currently under development. Oppenheimer supported his research and in May discussed the possibilities with General Groves and the head of Dupont operations Crawford Greenwalt. Hans Bethe had been appointed head of the Theoretical Division over Teller even though Teller had been involved with the project since 1939. He felt slighted by the decision and as a result found it difficult to fit in at Los Alamos in the theoretical division. He finally departed from work on the fission bomb. Being preoccupied with a thermonuclear weapon, Teller declined to work under Bethe on the theoretical calculations needed for an implosion to succeed. Oppenheimer eventually replaced him with Rudolf Peierls, a Jewish theoretical physicist who had worked under Werner Heisenberg as a student and had immigrated to England in 1939. Peierls had worked as deputy head of the British program under James Chadwick and now took up residence at Los Alamos. Oppenheimer encouraged Teller to stay on and work on the hydrogen bomb but his subsequent contributions to the fission bomb program would be minimal. During this time Seth Neddermeyer’s implosion tests had made little progress. Two people were recruited to help. George Kistiakowsky, a Harvard Chemist and explosives expert and James Tuck, a member of the British mission to Los Alamos. Kistiakowsky had been working on explosives development for the National Research Defense Committee since 1941 and Tuck had previously worked on the development of “shaped charges”. These were explosives used in gunnery shells that were designed to channel the direction of the explosive force for use against tank armor. Tuck proposed that this method might be applied to the implosion experiments to design an arrangement of charges called “lenses” that would produce a converging shock wave to properly squeeze a bomb core into implosion. In April 1944, new IBM calculating equipment arrived to also help the implosion design effort. This early computer clarified the calculations but also demonstrated the difficulty in achieving the desired results.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 546-549)

1944 | D-Day

Operation Overlord, which became known as D-Day, was the greatest amphibious invasion in history. It was commenced on June 6th, 1944 under the command of General Dwight D. Eisenhower off the shores of Normandy, France to overthrow Hitler's occupation of Europe. In the early stages of the assault, the Allied air forces dropped over 10,000 tons of bombs on the German defenses in France and over 7,000 fighter aircraft attacked what was left of the Luftwaffe air defenses. Scores of airborne drops were initiated behind German lines to secure key strategic points for the invasion and hold off repelling German forces. At the same time, roughly 4,000 ships and landing crafts ferried 176,000 men across the English Channel. By nightfall, five British and American divisions plus three airborne divisions secured the beachheads. Within a month, the allies had deployed almost a million soldiers with over 150,000 vehicles and a sustainable supply line built on the beaches by a system of stationary and floating barges called “Mulberries”. Hitler's Europe had been breeched. The assault eventually led to the defeat of The Third Reich and the perceived race with Germany to develop an atomic bomb ended. However, the Manhattan Project now had a life of it’s own and proceeded methodically with the focus of its efforts now aimed at the secondary target of Japan.

1944 | Emilio Segre

Emilio Segre made another important discovery in the early summer of 1944 that nearly doomed the plutonium bomb. A year earlier, Glenn Seaborg had indicated that the isotope Pu240 might taint plutonium when it was made from irradiated uranium. Pu240 had a spontaneous fission rate much higher than the plutonium isotope. When he tested prototype plutonium samples from the X-10 experimental reactor at the Oak Ridge facility, he discovered the rate for spontaneous fission was much higher than previously expected. The fission rate of the bomb grade plutonium being produced at the Hanford reactors would be even higher. While this meant that it would not need to be as highly refined as was first expected, it also meant plutonium would not be a suitable fuel to be used with a gun design. Before the uranium bullet and target in a gun design could form together into a critical mass the material would melt and fizzle due to the high rate of fission of plutonium. The option of removing the Pu240 traces that caused the accelerated fission in the plutonium had not been a consideration when building the facilities at the Oak Ridge facility. Designing, engineering and constructing the plant to handle this very toxic operation at this point in time would severely delay the project from affecting the outcome of the war. It was decided that the gun design would proceed using only enriched uranium. The only chance for a plutonium bomb would have to rely on perfecting an implosion design.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 546-549)

At Oak Ridge Tennessee, the gaseous diffusion plant built to enrich uranium at the final stage of refinement was behind schedule and had begun to threaten the uranium bomb project. Ironically, the program now had a viable gun design for a bomb without enriched uranium fuel and at the same time, plutonium fuel was being produced in quantity but without a working implosion design. A navy physicist named Philip Abelson had been working on a low enrichment uranium process of thermal diffusion for use in submarine propulsion since 1939. By 1944 he had designed and built a thermal diffusion plant using columns of pipes filled with uranium hexafluoride heated by naval steam generators and surrounded by flowing water for cooling. Thermal diffusion had been rejected for the Manhattan project because it could not enrich uranium to the necessary purity. In April 1944, Abelson contacted Oppenheimer through back channels to let him know of his progress. Oppenheimer realized that using semi-enriched uranium would vastly increase the efficiency of the pre-stage enrichment process at Oak ridge He and Groves had not considered using the different processes in tandem with one another. Upon realizing the mistake, General Groves immediately commissioned a scaled up 2100 column facility based on Abelson’s design to be built within 90 days alongside the 238,000-kilowatt power plant already completed at Oak ridge The electric plant would provide heat for the thermal diffusion process while they waited for the K-25 gaseous barrier diffusion plant to be completed. This improvisation put the delivery for bomb grade fuel back on schedule.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 551-553)

1944 | Pacific Offensive

Admiral Nimitz, the commander of U.S. Pacific fleet and the Marine Corps had pushed the Japanese back to their own territory by early 1944 and was advancing across the Solomon Islands. The U.S. Army under General Douglas MacArthur had moved up from Australia through New Guinea and into the Philippines. The Japanese were now effectively contained and completely on the defensive. Nevertheless, that defense was brutally defiant and the American forces paid a heavy price as they advanced. As the U.S. forces closed in on the Japanese home islands the battle for the Pacific became a horrific theater of death. The first main island objective on the march to mainland Japan was to capture Saipan and Tinian islands in the Mariana islands roughly 1500 miles from Japan. This would provide the U.S. Army Air Force with an airfield to launch a long range bombing campaign on the Japanese home islands. The Marines invaded Saipan first on June 15th, 1944. The Japanese attacked with suicide frontal assaults called “Banzai” charges. Records indicate that there were a total  of 14,000 U.S. military personnel casualties killed on Saipan . By contrast 30,0000 Japanese soldiers were killed and almost none surrendered. Even more harrowing was the fact that of 22,000 Japanese civilians were killed in the conflict. Several thousand of these people were persuaded by the propaganda of the Japanese military to climb high cliffs and commit suicide by jumping into the sea rather than face the invading U.S. forces. The Marines were able to take the smaller main objective of Tinian with only 300 killed and 1500 wounded. Once these islands were secure, construction of a massive airfield of six 8500-foot runways began. From Tinian island the U.S. Air Force would begin a brutal strategic bombing campaign against Japan with the newly deployed Boeing B-29 Super Fortress; the world’s first intercontinental bomber. The B29 was the first pressurized bomber ever built and could cruise at altitudes above 30,000 feet, well above the range of most fighters and antiaircraft artillery of the time. It had a maximum speed of 350 miles per hours and was designed to carry 20,000 pounds of bombs, with a mission range of 4000 miles.

1944 | Kamikaze

Japanese Forces began engaging U.S. naval vessels with suicide aircraft attacks.  These planes were normally only loaded with fuel for a one one trip and a normal bomb load and became the most fear weapon in the Japanese arsenal. They were known as the “Kamikaze” (divine wind) named after a legendary typhoon that had destroyed an enemy fleet intent on invading Japan in the 13th century. In a final act of defiance and desperation thousands of young Japanese kamikaze pilots forfeited their lives in a futile but frightening effort to slow U.S. Naval forces as they advanced in an island hopping campaign towards Japan. Because of the Japanese defense of the Marinas Islands, and the subsequent horrific assaults of Iwo Jima and Okinawa, it became evident that there would be no surrender by either Japanese soldiers or civilians in any future invasion of mainland Japan.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 554-557)

1945 | General Curtis Le May

Major General Curtis Le May took command of the Pacific Theater’s Strategic Bombing Air Forces in January of 1945. Le may had been commander of the 20th Bomber squadron based in India and China but had achieved limited results in the initial strategic bombing of Japan due to the distance involved ferrying fuel and munitions required to supply the Allied air bases to carry out effective missions against the Japanese home islands. The recently captured Marina islands of Guam, Saipan and Tinian now had a force of 345 new gleaming, polished aluminum skinned, B-29’s poised to be unleashed on the Japanese homeland. From the average citizen to the highest level of government, Americans were calling for attacks on Japan to finally avenge the bombing of Pearl Harbor. Revenge is what they wanted and it would be delivered in unimaginable ferocity in the form of area bombing of Japanese cities. The American political and military justification for area bombing of civilian targets laid in the fact that Japans’ war machine and production capacity was integrated into the civilian population areas. Prisoners of war that had managed to escape from the Japanese mainland reported evidence of this. By this time, nearly every urban Japanese home was involved in the production of weapons, ammunition or other materials to help the war effort. Women and children and the elderly had now become legitimate targets in the eyes of the U.S. military. Curtis Le may immediately began limited attacks on Japanese cities from Tinian Island. He knew that the most Japanese anti-aircraft munitions had been manufactured to detonate at high altitudes as they were designed to be effective against Allied Bombers at long range. Le may also knew that the majority of Japanese fighter aircraft had now been destroyed in attacks conducted against U.S. Naval Forces. In a daring strategy, Le may stripped his B-29 squadrons of defensive armaments to carry additional fuel and bombs and flew very low altitude bombing raids against Japanese cities below the effective range of their anti-aircraft defenses with incendiary bombs resulting in devastating effects.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 586-589)

1945 | Iwo Jima

Iwo Jima and Okinawa were the last targets planned for assault prior to a full-scale invasion of the Japanese mainland. Iwo Jima was 600 miles closer to the Japan than the Marinas, and the Japanese were using the island as a rudimentary radar base to launch fighter and bomber attacks on Le may’s B 29’s squadrons based on Saipan and Tinian. Iwo was a barren mass of volcanic ash with a total area of less than 7 square miles. A dormant volcano named Mount Suribachi dominated the landscape at one end of the island. Other than its two airfields it had little strategic importance. Nevertheless, it was decided that it would be taken by amphibious assault by the U.S. Marines. The Japanese military, understanding the importance of Iwo as a stepping-stone to a full-scale U.S. invasion, spent many months building an intricate network of underground defense positions. They deployed over 20,000 elite Japanese soldiers to defend it. After several weeks of U.S. naval and air force bombardment the assault of Iwo Jima commenced on the morning of Saturday February 19th. 1945. The marines were deployed to the beachheads with lightly armored landing craft and amphibious personnel carriers. The beachhead sand was composed of a dry black volcanic ash, which made it impossible to dig in . The Japanese defenders waited until the marines were fully ashore and then laid down a devastating barrage of mortar and artillery gunfire from their hidden positions in the high mountainous terrain. By the end of the first day 2,430 of the first wave of 30,000 marines were killed. It took nearly a month to secure the small worthless island. The defenders hid and died in ruthless defiance from allied forces and numerous requests for surrender. Each inch of ground required nothing less than an all out killing of the enemy, often by using flamethrowers and grenades to burn out and kill the underground emplacements of the defenders. The final victory cost 6,821 U.S. Marine lives and virtually all of the 20,000 Japanese defenders. Only 1,083 Japanese troops were captured. After Iwo Jima, the U.S. Marines successfully assaulted the island of Okinawa. The Japanese defended this island with the similar defiance and nearly no Japanese prisoners were taken. Approximately 12,500 U.S. soldiers died taking the island.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 592-595)

1945 | The Gadget

At Los Alamos, the latest lens explosive design for the implosion gadget had been successfully developed by early 1945. The design used truncated pyramid shaped blocks of two different types of explosives configured in a spherical assembly. The lens surrounded a tamper of uranium that encased the plutonium bomb core. The fast burning explosives of the outer layer would generate the spherical detonation wave and the slower burning explosives in the next layer would act to magnify, slow down and reshape the wave from a convex to concave shape that would fit around the spherical shape of the tamper. As the wave approached the tamper it passed through another layer of fast burning explosive to add additional strength to the implosion. Uranium was used for the tamper as it is the heaviest element other than plutonium and would smooth out irregularities of the detonation wave as it collapsed onto the bomb core. If it worked correctly the detonation wave would squeeze the plutonium bomb core with the pressure of thousands of atmospheres collapsing it onto itself and generating a fission chain reaction. Tests of the detonation lenses proved successful but it was still uncertain if a chain reaction would occur in the implosion design. A live test would be necessary using a bomb core of plutonium - the rarest and most expensive substance on earth. By early April, the Oak Ridge facility had produced enough U235 to make a critical mass. The final gun design would utilize a uranium bullet that would fire into a target assembly of three uranium rings to create the chain reaction. Both the theoretical and engineering teams were convinced that the gun design would work. Near critical mass experiments, carried out by Otto Frisch in late 1944, had proved a fast-neutron chain reaction would occur in uranium. Frisch had been one of the first scientists to calculate the required size of a critical mass of uranium required for an Atom Bomb and was now in charge of fission testing of enriched uranium at Los Alamos. If a test of the implosion design could produced an explosion, there was no doubt “Little Boy” would also produce one.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 574-576, 612)

1945 | Bombing of Tokyo

Full-scale area bombing of Japanese cities commenced on March 9th 1945. From the recently captured Marina islands, 334 B-29’s loaded with various types of incendiary bombs took to the air. The pathfinder lead planes arrived a little after Midnight above the district of Shitamachi in Tokyo where over 750,000 people lived in houses built mostly of wood and paper. The wind was blowing at over 15 miles per hour. The pathfinders marked the area with clusters bombs in an X, and the following main force dropped their ordinance in 500-pound clusters that broke apart a few hundred feet above the ground at intervals spaced approximately a third of a square mile apart. The wind increased and what followed was far worse than any firestorm unleashed on Germany. It later became known as a “Conflagration”. Heat from the firebombing fueled the high winds resulting in spiraling columns of super-heated fire that resembled massive tornados. The heat was so intense that in shallow canals of the city the water boiled. More than 100.000 men, women and children died that night and over a million civilians were wounded. An additional million people were left homeless. This first attack was only the beginning of the horror to be inflicted on Japan from above. Over the next few months, fifty-eight major cities in Japan were fire bombed in hundreds of raids. The carnage subsided only when the B-29 crews began to run out of bombs.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 596-601)

1945 | Harry Truman

Franklin Delano Roosevelt died on April 12, 1945. The nation grieved the man who served four terms as President of the United States and had guided Americans out of the great depression and through World War II. Vice President Harry S. Truman was sworn in as President and within 24 hours was briefed on the Manhattan project by Secretary of War Henry Lewis Stimson. Truman had been aware of the projects existence but did not know that two variations of an atomic weapon were nearly ready. As the war with Germany came to a close, Truman was immediately faced with how to deal with the Soviet Union in post war Europe. Should an invasion of Japan prove necessary the U.S. would reluctantly need help from Stalin’s Red Army and also have to negotiate the post war theater there, as well as settling the affairs of Europe with the Russian dictator. Truman realized that if the atom bomb became a practical weapon before the end of the war then the U.S. might not need assistance from Russia to finish off Japan. He knew Japan had already opened a dialogue with Russia to discuss possible negotiations for a conditional surrender. The possession of an atomic weapon would give the U.S. considerable negotiating power at the forthcoming Potsdam conference where he would meet with Stalin and Churchill to decide on the postwar occupation of Germany and its annexed territories.

1945 | Henry Stimson

Henry Stimson had been in line for the Vice Presidency under Roosevelt but was considered too valuable an asset by FDR for the back seat position of Vice President and was appointed as the Secretary of War. After FDR’s death Secretary Stimson formed the Interim Committee at the request of President Truman to discuss the possible use of an atomic weapon against Japan. An ad hoc Target Committee, that included many senior scientists from the Manhattan Project, was formed to make selections from what were still left of Japan’s target cities. The initial recommended list, in order of priority, were: Kyoto, Hiroshima, Yokohama, the Kokura Arsenal Complex and the city of Niagara. U.S. Secretary of War, Henry Stimson, hated the bombing of cities even though he knew the Japanese had interwoven war industries into their civilian populations. On May 30th he called a meeting with General Groves prior to the release of the target report and gave him a direct order...“ This is the one time I am going to be the final deciding authority. No one is going to tell me what to do on this … I don’t want Kyoto bombed.” Kyoto was the cultural center of Japan, a former ancient capital full of religious temples and ancient shrines. As a result, Kyoto would be saved and it was removed from the target list. Key scientists from Los Alamos including Oppenheimer were asked to join the Interim committee as a scientific panel of advisors. The full compliment of the committee met on March 31st 1945. After introductions, Arthur Compton offered an overview of the atomic bomb and the future generation of such weapons including the thermonuclear “Super” bomb. Oppenheimer then described the destructive force of the first “crude’ weapons to be in the range of 2,000 to 20,000 tons of TNT and future improved versions to be in the range of 50,000 to 1000,000 tons of TNT. The hydrogen bomb, if possible to develop, might range from 10 million to 100 million tons of TNT. Many people in the room were clearly scared by the predictions. The discussion moved onto the development of stockpiles of such arsenals and infrastructure to support them in the near future. The recipe for the arms race that dominated the second half of the century was being written before the technology had even proved itself. The committee then addressed the question of control of the technology. While the United States had the lead in the development of atomic weapons and energy technology, the fundamental knowledge of atomic physics was now widespread. Oppenheimer, echoing Niels Bohr’s recommendations to both Roosevelt and Churchill in 1944, proposed the committee should consider the free exchange of information with other nations for the promotion of atomic physics for peaceful purposes and to establish international control of nuclear weapons. Stimson asked him “What would be the position of democratic governments as against totalitarian regimes under such a program of international control coupled with scientific freedom?” Oppenheimer replied that he doubted if the U.S. could stay ahead permanently under such circumstances. As the committee moved to lunch, and for the rest of the day, the final question was whether the Atom Bomb could be used in some sort of demonstration to convince the Japanese to surrender. After debating several scenarios most members agreed that for the weapon to have real psychological value no advance warning could be given and the weapon must be used to cause real damage and casualties. The decision of the committee was immediately hand delivered to President Truman for endorsement.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 640-649)

1945 | Trinity

Trinity would be largest physics experiment ever attempted, and if successful, the first time the raw power of E=mc2 would be unleashed in the form of an explosion. It is believed that Oppenheimer provided the name for the test site in reference to the divine trinity of Brahma (the Creator), Vishnu (the Preserver), and Shiva (the Destroyer) as described in the sacred Hindu text of the Bhagavad Gita. Oppenheimer was an admirer of Hindu philosophy and often quoted its scriptures. The site for the test had finally been selected from eight possible New Mexico locations in February 1944 roughly 60 miles from Los Alamos. The Army acquired the land belonging to the McDonald ranch and began renovating it into a field laboratory for the test. The Army Corps of Engineers built a series of observatory structures around the site and contractors were brought in to assemble two towers; one for ground zero and one for a 100 ton TNT explosion to test the scientific recording equipment that would measure the implosion test. The 100 foot Zero Tower was shipped in prefabricated sections to the site. It had a removable floor section in the top of a covered tower and was equipped with a $20,000 electrical heavy winch to haul the implosion device to its resting position above ground. By May 31, enough plutonium had been shipped from Hanford to begin the assembly of the device and after several minor design changes the first workable “Gadget” was nearly ready. On May 7th the 100-ton TNT stack, the largest single chemical explosion in history, was detonated simply to test the instruments and practice the routines of the implosion test.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 651-654)

The Trinity Test was scheduled for detonation on the morning of July 16th weather permitting. Once assembled the plutonium core made its way from Los Alamos to the trinity site on Friday the 12th. The two hemispheres of nickel-coated plutonium (which the team asked the army for a receipt for) were assembled into the hallowed out plug of tamper by a nine-man crew. Then, the ordinance team secured the assembly into the spherical high explosive encasement. After some last minute adjustments the following morning, the “Gadget” was hoisted by winch up to its resting place in the tower. There the delicate insertion of the detonators for the explosives began. On Sunday evening Oppenheimer climbed the tower to make a final personal inspection. At about 2am a desert rainstorm began accompanied by lightning threatening to accidentally explode the gadget prematurely. The project’s meteorologist Jack Hubbard had accurately predicted the storm. Hubbard had recommended the test be postponed until the following day, but General Groves rejected the recommendation as he wanted to deliver news to Truman at Potsdam by Tuesday the 13th. Groves threaten Hubbard for an accurate forecast to the minute early that morning. Hubbard predicted accurately that the storm would pass by 4am.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 652-670)

The countdown began at 525am. Bets were placed by senior members of the scientific team on the yield of the blast. Fermi, presumably with a smirk and to the irritation of Gen. Groves, opened a second line of betting on whether the gadget might ignite the atmosphere and destroy the earth. There were more than a few takers. At 5:54:45, the electrical circuits closed and thirty-two detonators simultaneously fired. As planned the lens explosives created the detonation wave and collapsed on the tamper of bomb core with millions of pounds of pressure per square inch. The resulting chain reaction that occurred mimicked, for a millionth of a second, the moment the Universe was created. The explosion went through a myriad of phases in millionths of a second that were unperceivable to human eyesight. An expanding ball of nuclear fire at temperatures of tens of millions of degrees met the ground and then developed into a massive outward burst of radiation, heat and resulting shockwave as it began to cool and became visible to the naked eye. Within a second it expanded to a fireball about 2500 feet across and then began its transformation into the now classic shape of a mushrooming cloud. Observers were knocked off their feet at a distance of two miles from ground zero from the resulting the shock wave and the flash from the explosion was seen from hundreds of miles away. The blast was estimated to be the equivalent of roughly 21,000 tons of TNT. As the blast subsided, Oppenheimer silently remarked to himself a passage from the Bhagavad Gita – “Now I have become death…the destroyer of worlds.”
(The Making of the Atomic Bomb by Richard Rhodes, pp. 672-677)

As a small sun descended upon the earth in New Mexico at Trinity, the components for the ‘Fat Man” and ‘Little Boy” bombs were already on there way to the their destinations for deployment in the Pacific. President Truman received a wire confirming the success of the Trinity Test at the Potsdam Conference. He casually related to Joseph Stalin that the U.S. had a new weapon of unprecedented power at its disposal. Stalin had already received the news from soviet spies in the U.S. and in an unimpressed fashion congratulated Truman and expressed that he hoped it would be put to good use against the Japanese. No one knew it then, but the cold war had just begun. The Soviet Union was already working on their own atomic weapon and was only about a year or two behind the United States. On July 26th Truman released the Potsdam Declaration to the press from occupied Germany calling for the immediate unconditional surrender of Japan. It ended with the statement: “We call upon the government of Japan to proclaim now the unconditional surrender of all Japanese forces…The alternative for Japan is prompt and utter destruction.”

The Japanese believed unconditional surrender meant they would have to give up the political structure supporting their Emperor whom they considered a living God on earth. Political, religious and cultural aspects of Japanese society were all tightly interwoven in this ideology. The U.S. believed that the Japanese would reject surrender even if it permitted the Emperor to remain on the throne. If the declaration had allowed this condition it might also be perceived as an offer to allow the preservation of the militaristic faction of the government who actually ran the nation and who had started the war. The Japanese military and government rejected the declaration. One hundred million strong, the Japanese were determined to defend an invasion of the home islands with every able-bodied man woman and child. It was estimated, after the bloody battles for the Marianas, Iwo Jima and the recent assault on Okinawa, that and invasion of the Japanese homeland might ultimately cost the lives of up to 500,000 American soldiers. Historians debate whether an invasion would have actually been necessary. Much evidence indicates that Japan was ready to surrender, and would have, if the language of the Potsdam declaration had been crafted more carefully. The directive to use the atomic bomb was drafted by General Groves on July 24th and approved by the secretary of War and Secretary of State under the discretionary authority of President Truman.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 685-692)

1945 | Little Boy

The day the Prime Minister of Japan rejected the Potsdam declaration, C47 aircraft arrived at Tinian Island carrying assembly equipment and the uranium 235 target rings for the “Little Boy” gun bomb. The previous day the heavy cruiser USS Indianapolis had delivered the “Little Boy gun assembly and the U235 bullet. At the same time, three B-29s departed from the U.S. carrying a “Fat Man” high explosive pre assembly. The assembly of the bombs began. “Little Boy” would be ready on July 31st . On its return voyage, the Japanese submarine I-58 torpedoed the Indianapolis in the Philippine Sea. The older heavy cruiser lacked sonar and it was traveling without an escort under strict radio silence. The Japanese sub I-58 fired 5 torpedoes in a spread and hit the ammunitions and fuel depots instantly knocking out the ships electricity and therefore disabling its radio. No distress call could be sent and he ship sank in a matter of minutes. Of the 1,196 men aboard, only 850 sailors managed to abandon the vessel before it went down. The ship was not due in port for days. The Survivors, many who were injured, spent nearly 5 days without food or water in the shark-infested sea. There were only a few lifeboats and many drowned after being pulled down by their waterlogged life jackets. Dozens of the survivors were eaten alive by sharks and some were even killed each other with knife fights causes by panic and hallucinations caused by drinking seawater. By sheer luck a navy plane spotted what was left of the sailors on the morning of August 2nd. A major rescue effort commenced. Of the 850 men who escaped the ship before it sank, only 318 were rescued. Most died of drowning from exhaustion.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 685-692)

1945 | Hiroshima

The final target list for the dropping of the atomic bomb was Hiroshima, Korkura and Niigata. In case of bad weather, an alternate target, the city of Nagasaki, was added. On August 6th, at approximately 2:30AM, Colonel Paul Tibbets took off from Tinian island in a B-29 he had named Enola Gay after his mother. At 15,000 pounds over weight, the specially modified bomber barely became airborne. It was carrying thousands of gallons of extra fuel and one 9,700-pound atomic bomb. As a precautionary measure “Little Boy” was not yet armed; as it was feared it might detonate if the plane crashed on take-off. Inscribed on the bomb were dozens of signatures including a greeting from the USS Indianapolis. At 3:00AM, as the Enola Gay flew low at 5000 feet over Saipan, the final procedure to arm the weapon began. Weapons officers “Deke” Parsons and Lt. Morris Jeppson crawled into the unheated bomb bay to install the arming assembly. At 5:52 the B-29 passed Iwo Jima, and climbed to 9,300 feet where it met two B-29 escort planes. As the group made their way north by northwest, the crew plotted their final course towards Hiroshima. Forward weather planes reported that there was only twenty percent cloud cover over the city confirming it as the primary target. At 7:30AM, weapons expert Deke Parsons crawled back into the bomb bay to make one final check on “Little Boy”. The Enola Gay then began climbing to 31,000 feet and at 8:40AM leveled off at 328 miles per hour. The escorts dropped back and the crew donned heavy flack suits at about 12 miles from the outskirts of the city. No fighters or anti-aircraft fire challenged the lone B-29. As Hiroshima entered the cross hairs of Bombardier Major Thomas Ferebees’ Norden sight, the plane’s bomb bay doors opened. Ferebees found his aiming point at the Aioi Bridge near the center of the city and the bomb fell away.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 699-699)

“The elongated trash can with fins” spun and whistled. About thirty-five seconds into free-fall, a barometric switch measured the altitude at 7000 feet and primed the secondary arming system. Antennas sticking out of the back section of the bomb began to record the reflected radio signals the bomb was transmitting towards the ground. At 1,900 feet, forty-three seconds after leaving the plane, the last signal was recorded and an electrical charge fired a conventional artillery blast. The U235 bullet shot down the length of ‘Little Boys’ encased gun barrel and met the three uranium target rings at the other end. As the two critical masses collided, a single uranium nucleus became unstable, wobbled and tore apart. As it split it, it then bombarded and spit two more nuclei, and then four more, and then eight more... As the process exponentially repeated the mass of the colliding uranium began to disintegrate and travel through the equals sign (=) of Einstein’s E=mc2. The whole process of the chain reaction took only a few millionths of a second. As the uranium disintegrated it emerged on the other side of the equation as pure energy - in the form of heat. For a brief moment, at the peak of the reaction, that energy became hotter than the center of the sun. As this heat met the air around it the bomb exploded with the force of 12,500 tons of TNT.

The flash of light from the explosion over Hiroshima would have been visible from the moon. The heat generated from the explosion instantly disintegrated nearly all organic matter up to 600 yards away from ground zero. Thousands of people within a half-mile radius were carbonized into black char in a fraction of a second. People closer to the center were completely vaporized leaving only silhouettes of their bodies immortalized in solid granite of buildings from the intensity of the flash. Miles away the flash produced shadows deeply pigmented into human skin that lasted for months. The blast wave that followed, traveled at two miles per second for several hundred yards disintegrating nearly every structure in its path. Of the 76,000 buildings in the city 48,000 were totally destroyed and 22,000 were severely damaged in a matter of seconds. The city of Hiroshima, which had a population of 400,000 suffered 8000 people killed instantly and between 70,000 and 100,000 dead within the first day from fatal injuries. There were an additional 130,000 people wounded; 43,000 critically. Many of the injured later died from wounds or sickness caused by the radiation released from the bomb. More recent estimates now place the total death toll by the end of 1945 at 140,000 and 200,000 after five years. Roughly 54% of the cities total population of men women and children eventually died from the explosion. A similar percentage of animal life that had existed in and around the city also died. A Japanese study concluded that “The whole of society… was laid to waste to its very foundations”.
(E = mc2: A Biography of the World's Most Famous Equation by David Bodanis, pp. 163-173)

1945 | Fat Man

In Tokyo, news of the attack arrived but specific details were unclear. Military and civilian leaders argued over the acceptance of defeat. The civilians felt the atom bomb provided a way to accept unconditional surrender without shame but the military refused. The Japanese Foreign Minister continued to pursue negotiations with the Soviet Union up until August 8th. When Stalin learned of the attack he was surprised and immediately ordered the Red Army to attack the Japanese forces in Manchuria. Between August 7th and 10th six million leaflets were printed and dropped on major cities in Japan with populations over 100,000. The text of the message described one atom bomb as “the equivalent in explosive power to what 2,000 of our giant B-29’s can carry on a single mission”. It went on to say “ make inquiry as to what happened to Hiroshima”…”Petition the Emperor to end the war”. As a million and a half Soviet troops prepared to engage the Japanese on the border of China, a B-29 named Bock’s Car took off from Tinian Island. at 3:47am carrying the plutonium bomb named “Fat Man”.
(The Making of the Atomic Bomb by Richard Rhodes, pp. 714-734)