How the Manhattan Project Came into Being

On August 6, 1945, Paul Tibbets, the pilot of the B-29 aircraft named Enola Gay, dropped an atomic bomb over Hiroshima, Japan. Known as 'Little Boy,' the bomb unleashed an explosion equivalent to 15,000 tons of TNT, devastating nearly every structure within a mile of ground zero and causing a massive firestorm that consumed the city. Approximately 70,000 people perished instantly, with the death toll eventually reaching 100,000 by the end of 1945 and 200,000 after five years due to the effects of radiation [source: U.S Department of Energy]. Three days later, on August 9, a second bomb was dropped on Nagasaki, an industrial city. This bomb, named 'Fat Man,' caused the immediate deaths of around 40,000 people, with the total rising to 70,000 by the year's end and 140,000 after five years [source: U.S. Department of Energy]. Japan formally surrendered to the Allied forces on August 14, 1945, bringing an end to World War II.

Gallery of Nuclear Bomb Photographs

The creation and deployment of the atomic bomb, the most devastating weapon ever created by humanity, is considered one of the most significant and controversial milestones of the 20th century. Its unparalleled destructive power and its representation as a tool of domination sparked the intense nuclear arms race between the United States and the Soviet Union in the post-war years. The nature of modern warfare had already evolved drastically in the early 20th century with the advent of airplanes, machine guns, and biological and chemical warfare, all of which had reshaped military strategies and caused widespread devastation. However, the atomic bomb was a new and different force. While some believed its mere existence could end all warfare, others feared that it could lead to the total annihilation of humanity.

The Manhattan Project, the secret initiative by the United States to develop atomic bombs for warfare, was a broad term covering the various people, places, and resources involved in atomic research during World War II. Even now, opinions remain divided on whether the decision to use the bomb on Japan was justified, with some believing it ended the war and saved countless lives, while others argue that Japan would have surrendered regardless.

How was it all accomplished? Who were the key figures? And why was it called the Manhattan Project? In this article, we will delve into the Manhattan Project and explore how an extensive network of scientists and military personnel succeeded in creating the most powerful release of energy the Earth has ever seen.

­

The Discovery of Nuclear Fission

To fully understand the Manhattan Project and the bombings of Hiroshima and Nagasaki, it's essential to look at the advancements in physics leading up to World War II. Between 1919 and the early 1930s, scientists were making key discoveries about the structure of the atom. In 1919, at Manchester University in England, New Zealand physicist Ernest Rutherford identified the protons, positively charged particles within the nucleus of the atom. Alongside the negatively charged electrons orbiting the nucleus, they make up the fundamental building blocks of the atom.

There was a significant challenge -- physicists couldn't understand why certain elements had different atomic weights. This puzzle remained unsolved until 1932, when James Chadwick, a colleague of Rutherford, discovered the neutron, a neutral subatomic particle. Neutrons, sharing space with protons in the nucleus, revealed why elements could have varying atomic weights. For example, carbon typically has 6 protons and 6 electrons, but the number of neutrons could vary, leading to different isotopes of the same element with different masses.

During this period, scientists began using particle accelerators to bombard atomic nuclei in an effort to split atoms and release energy. Early attempts yielded little success — the first particle accelerators fired protons and alpha particles, both of which were positively charged. Despite their speed, these particles were easily repelled by the positively charged atomic nuclei, and renowned physicists like Rutherford, Albert Einstein, and Niels Bohr believed that harnessing atomic power was nearly impossible.

Everything changed in 1934 when Italian physicist Enrico Fermi suggested using neutrons for bombardment. Because neutrons have no charge, they could penetrate an atom’s nucleus without being deflected. Fermi successfully bombarded various elements, creating new, radioactive elements in the process. What he unintentionally discovered was the process of nuclear fission. This breakthrough was formally recognized in 1938 by German scientists Otto Hahn and Fritz Strassmann, who succeeded in splitting uranium atoms into smaller parts.

Uranium, known as the heaviest naturally occurring element on Earth, played a significant role in many of the early processes and garnered considerable attention in the field of physics for several reasons. With 92 protons, uranium is the heaviest natural element, while hydrogen, by comparison, is extremely light with only one proton. However, the real intrigue of uranium lies not in the number of protons, but in the unusually high neutron count within its isotopes. One such isotope, uranium-235, contains 143 neutrons and is highly prone to undergo induced fission.

When a uranium atom undergoes fission, it essentially loses mass. Einstein's renowned equation, E = mc², where E stands for energy, m represents mass, and c is the speed of light, illustrates how matter can be converted into energy. The greater the amount of matter, the more energy can be generated. Uranium, being massive with its abundance of protons and neutrons, loses more matter when it splits, resulting in the release of substantial amounts of energy, even though the mass loss is minuscule.

Additionally, extra neutrons are released when a uranium atom splits. Given that a pound of uranium contains trillions of atoms, the likelihood of a stray neutron striking another uranium atom is exceedingly high. This caught the attention of the physics community — a controlled chain reaction could potentially generate safe nuclear power, while an uncontrolled reaction held the destructive potential of devastation.

In the following section, we will delve into the U.S. decision to develop a nuclear bomb.

The German Threat

By 1939, news of nuclear fission spread swiftly from Europe to America, and several top physics labs in the U.S., including Ernest Lawrence’s at UC Berkeley, began exploring the potential of harnessing uranium for energy production.

The 1930s were a pivotal period in physics, but also filled with tension. As World War II raged on after Hitler’s invasion of Poland, the fear that Germany might be developing nuclear weapons led to concerns. Prominent physicists like Leo Szilard, Edward Teller, and Eugene Wigner, who had fled Europe to escape the war, urgently sought to alert the U.S. government about the looming threat of a German-built atomic bomb.

Alarmed by the potential threat, Albert Einstein and Leo Szilard penned a letter to President Franklin D. Roosevelt, urging action on the possibility of a nuclear weapons program. After consulting with economist Alexander Sachs, Roosevelt took the initiative to form the Advisory Committee on Uranium, appointing Lyman J. Briggs to lead the effort.

The ensuing two years were fraught with uncertainty. The U.S. was uncertain of the amount of uranium required, the costs involved in constructing a bomb, and how much time was available to develop a working weapon. Meanwhile, research into extracting uranium-235 from uranium remained inconclusive.

The pace of progress quickened with the involvement of Vannevar Bush, who, as the president of the Carnegie Foundation, was appointed by Roosevelt in the summer of 1940 to chair the National Defense Research Committee. Bush integrated the Uranium Committee into this new committee, ensuring better funding and security for scientists. By June 28, 1941, Bush was made director of the Office of Scientific Research and Development (OSRD), and the National Defense Research Committee became an advisory body to the OSRD. The Uranium Committee was then renamed the Office of Scientific Research and Development Section on Uranium, with the code name S-1. If all these name changes are confusing, it wasn’t just the public who struggled to keep up with the White House's handling of the bomb program.

In July 1941, Bush got the official boost he needed to kickstart the project. The British MAUD Committee, which had its own nuclear weapon initiative, published the MAUD Report. Despite England’s wartime strain, their theoretical input into the design of the bomb proved crucial. The report gave confidence to many that creating a nuclear bomb and enriching uranium-235 were feasible. With additional funding, Bush mobilized several research teams, predominantly from universities like Berkeley and Columbia. Lawrence alone secured $400,000 for his work in electromagnetism. Though secrecy remained a priority, more money allowed scientists to work in concealed locations — for instance, physicists Enrico Fermi and Arthur Compton conducted the first nuclear chain reaction beneath the stands at Stagg Field, the racket courts at the University of Chicago, in 1942.

Before long, the U.S. Army became involved. To learn more about the organization of the Manhattan Project, turn to the next page.

Manhattan Project Organization

By March 1942, the Army Corps of Engineers became actively involved in S-1 meetings, and on September 18, Colonel Leslie R. Groves was appointed to lead the project, now formally called the Manhattan Project. With a strong engineering background, having overseen the Pentagon's construction, Groves proved to be an adept administrator, playing a pivotal role in the bomb's success within a remarkably short timeframe.

In the following year, Groves selected several key locations across the U.S. to help complete the bomb, including Oak Ridge, Tennessee (Site X), and Hanford, Washington (Site W). These were large-scale facilities dedicated to uranium and plutonium production. When Groves appointed Robert Oppenheimer, a professor of theoretical physics at Berkeley, as director of Project Y, the two chose Los Alamos, New Mexico, to serve as the central hub for the Manhattan Project.

Los Alamos, along with the sites in Tennessee and Washington, were remote areas selected for their security advantages. However, during peak production, these locations were bustling hubs of activity. The barren New Mexican mesa in Los Alamos was transformed into a small city, complete with laboratories, offices, dining facilities, and housing for everyone involved. Oppenheimer worked tirelessly to assemble the nation’s top scientific minds, and for nearly three years, from the fall of 1942 until the bombing of Hiroshima on August 6, 1945, thousands of individuals overcame numerous challenges in constructing the atomic bomb.

Security at Los Alamos was extremely stringent. People were often prohibited from contacting family or friends for the entirety of their stay at Site Y. Clearance procedures were strict, and the complex was surrounded by barbed wire. The Manhattan Project was shrouded in such secrecy that many individuals didn’t even understand the true nature of their work until news broke of the atomic bomb's explosion over Hiroshima.

At Los Alamos, two distinct types of nuclear bombs were developed: an implosion bomb and a gun-triggered bomb. After significant improvements were made to the implosion design, a location was selected to test the first nuclear bomb. Alamogordo, a desert site around 210 miles south of Los Alamos, was chosen and named "Trinity" for testing a plutonium bomb. Oppenheimer is said to have recalled the lines from John Donne's poem, "Batter my heart three-person'd God," and felt it was an apt comparison. At 5:30 a.m. on July 16, 1945, the bomb was detonated, producing an enormous blast that temporarily blinded several scientists observing the event: the Atomic Age had officially begun.

Less than a month later, the United States dropped both the implosion bomb and the untested gun-triggered bomb on Japan to force a surrender. While the bomb is often credited with bringing an end to the war by halting ground combat in Japan, its creation marked the beginning of a nuclear arms race that would shape the second half of the 20th century.