What Was the Manhattan Project?

During World War II, there was a push to create a “super bomb” that could push the Axis Powers into surrendering. It was called the Manhattan Project.

Aug 8, 2022By Owen Rust, MA Economics in progress w/ MPA
manhattan project atomic core 1945
A photograph of an atomic core created during the Manhattan Project, via Carnegie Mellon University, Pittsburgh


Unlike World War I, World War II quickly appeared to be a fight to the brutal finish. Allied troops would need to battle their way deep into Berlin and Tokyo to defeat the Axis Powers once and for all. How many Allied soldiers and innocent civilians would die in this war of attrition? To attempt to end the war without such extreme loss, a secret program was begun in late 1942 to create a “super bomb” that could decimate a city. It was predicted that a bomb of this magnitude would lead Germany and/or Japan to seek a peace agreement rather than continue a losing war. Here is a look at the secretive and successful Manhattan Project.


Summer 1942: Total War

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German dictator Adolf Hitler meets with the Japanese foreign minister (center), via the United States Holocaust Memorial Museum, Washington DC


On September 1, 1939, Germany invaded Poland, sparking the outbreak of World War II in Europe.  In Asia, Japan had been engaged in a brutal war with China since 1937. Germany and Japan, along with Italy, joined forces and created the Axis Powers. By 1942, the three Axis Powers were engaged in total war against the Allied Powers, consisting of Britain, the United States, the Soviet Union, and China. A fifth Allied power, France, had been completely defeated in 1940 by Germany.


Initial Axis victories in 1940 up through early 1942 had created tremendous amounts of territory that needed to be liberated. In the Soviet Union, Germany had the Red Army on the brink of defeat near Stalingrad. In Asia and the Pacific, Japan had taken many island chains and controlled the bulk of the Pacific coast in Asia. Fighting through all of the Axis-controlled territories could take years and cost millions of lives. Many wondered if there was a better way to secure victory over the radical Axis Powers, who were willing to fight fanatically. Unlike World War I, this war seemed unlikely to end in an armistice; only unconditional surrender would be acceptable.


Originals of Nuclear Energy

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An image explaining nuclear fission, via Lindau Nobel Laureate Meetings


In the background of World War II was the recent discovery of nuclear fission. On February 11, 1939, German scientists published the first theoretical exploration of nuclear fission. By splitting the atom and achieving a chain reaction, tremendous energy could be generated. Quickly, scientists realized that the tremendous energy created by fissile material like uranium could be used to create massive explosions.

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In February 1940, the US Navy allocated funding for nuclear research for the first time. Although the US was not involved in World War II at the time, it was firmly allied with Britain, which was actively fighting Nazi Germany. Britain embarked on its own atomic weapons research only a month later. By mid-1941, although the US had still not entered the war, both the US and Britain had engaged in substantial nuclear research, finding that a super-explosive was possible. In October 1941, the US military took over the growing body of nuclear research in the country based on the beliefs that it could be militarily useful and that only the central government could effectively coordinate such complex activities.


August 1942: Birth of the Manhattan Project

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Scientists conducting nuclear research as part of the Manhattan Project, via the National Museum of Nuclear Science and History’s Voices of the Manhattan Project


The US entered World War II after the Japanese attack on the US Navy at Pearl Harbor, Hawaii on December 7, 1941. By this point, the US had already been supplying military equipment to Britain in its war against Germany through the Lend-Lease Program, as well as to China and the Soviet Union. Thus, America was not caught completely by surprise when it came to World War II mobilization. On August 13, 1942, the Manhattan Project was officially established, with its first headquarters in the Manhattan borough of New York City.


With the Manhattan Project, British efforts at a super bomb eventually merged with those of the Americans. Although British scientists had initially provided expertise in late 1941 and early 1942, there was hesitation in combining weapons projects. The British had started nuclear weapons research earlier than the United States, but in 1942, they transferred their research efforts to Canada. With the two nuclear projects being in close proximity, it only made sense to combine their efforts, especially given the size and complexity of the projects. In 1943, at the Quebec Conference, the British officially consolidated their efforts under the Manhattan Project.


1943: Work Moves to Los Alamos

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A photograph of the main gate for the Manhattan Project at Los Alamos, New Mexico, via the National Park Service


In early 1943, the British and American nuclear research efforts coalesced in Los Alamos, New Mexico. The US military was tasked with building secret laboratories near the mountains in the northern part of the state, far from prying eyes. Axis espionage and/or sabotage could derail the entire project, especially given the rarity of materials like enriched uranium.


Physicist J. Robert Oppenheimer was selected to lead this laboratory complex and suggested the location in rural New Mexico. As most researchers were professors, equipment had to be transported to the remote labs from various universities. One of the researchers, Enrico Fermi from the University of Chicago, had achieved the first self-sustaining nuclear reaction in December 1942. His reaction had been achieved on squash fields on the university’s campus!


An Enormous Project

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A photograph of workers at a nuclear research site in Oak Ridge, Tennessee during World War II, via the National Archives, Washington DC


Work on the Manhattan Project did not just occur at Los Alamos, New Mexico. Laboratories were also built at Oak Ridge, Tennessee and Hanford, Washington. US Army General Leslie Groves chose the Oak Ridge and Hanford sites, and all three sites were chosen because they were remote, sparsely populated, and far enough inland to be safe from potential enemy attacks.


In Tennessee, workers made enriched uranium; in Washington, they made plutonium. These two radioactive elements would create the fissile core of the proposed super bombs. At Los Alamos, these fissile cores would be constructed into weapons. Up to 130,000 people worked on the Manhattan Project in total and spending cost almost $2 billion. Of course, to maintain secrecy, most of these workers did not know what their tasks were intended to accomplish.


Fears of Axis Wunderwaffe

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A museum exhibit of a German V-2 rocket, which was a late-war “super weapon” targeting Allied cities in Europe, via the National Museum of the US Navy, Washington DC


Germany, rather than Japan, was seen as a major threat in developing a similar super bomb. Many Manhattan Project physicists, such as Albert Einstein, had emigrated to the United States shortly before the war instigated by Nazi Germany. Einstein actually warned the US of such a bomb race in August 1939. Germany had its own atomic bomb project during the war, known as Uranverein. Up through 1943, the Allies worried that Germany was on the brink of completing its own atomic bomb.


Although Allied intelligence between 1942 and 1944 eventually revealed that Germany was not on the brink of developing a super bomb, it was creating high-tech new “wonder weapons,” or wunderwaffe. These included jet fighters like the Me-262, rocket fighters like the Me-163, and cruise missiles like the V-1 and V-2. The V-2 rocket, which could not be intercepted, could strike London, Antwerp, or other cities. Thus, efforts to complete the atomic bomb continued even as Germany appeared on the verge of defeat: its wonder weapons might suddenly turn the tide of war.


1944-45: Painstaking Progress  

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A map showing the many necessary sites to make the Manhattan Project a success, via Carnegie Mellon University, Pittsburgh


Until 1944, not enough uranium or plutonium had been processed to make a single bomb. However, breakthroughs in late 1944 and early 1945 dramatically increased the amount of these radioactive elements. Now, work shifted from theoretical research to constructing the actual bomb. Tremendous efforts were made to ensure that work progressed, as the rigors of World War II made supply and manpower shortages common. Entire methodologies for working with uranium and plutonium had to be created, as these were highly volatile and toxic elements.


Even though Germany surrendered unconditionally on May 8, 1945, Japan still held out. Project Y, the project to create the atomic bomb, was completed in early summer. The new bomb had to be tested. After years of theory, would the device work in practice?


July 16, 1945: The Trinity Test

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A test of conventional high explosives on May 7, 1945 is conducted to calibrate the equipment needed to test the first atomic bomb, via the Los Alamos National Laboratory


In September 1944, a site was chosen to test Project Y’s results. The Alamogordo Bombing and Gunnery Range, which was largely flat and windless, would allow for secrecy and the most accurate testing of the bomb’s effects. Giant steel structures were created to withstand the expected forces of the explosion. On the early morning of July 16, 1945, the Trinity Test was conducted, successfully detonating the first nuclear bomb in history.


The bomb (or, technically, device) was known as Gadget and produced an explosion with the equivalent force of 21 kilotons (thousand tons) of TNT. This was a more powerful explosion than expected and signaled that actual bombs would be highly effective. The explosion produced a mushroom cloud that extended up to 38,000 feet. A new age, the nuclear age, had begun with a bang.


Success But Controversy

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A screenshot from an August 1945 newsreel in which US president Harry S. Truman announces the use of the atomic bomb on Japan, via the National Cable Satellite Corporation


The Trinity Test proved the success and feasibility of an atomic bomb. Japan, the sole remaining Axis Power, would be the target of this new weapon. But should a public test be made to reveal the power of the new weapon, hopefully convincing Japan to surrender? Ultimately, it was decided that a test would not persuade Japan to surrender. Some feared that using the atomic bomb would result in a potentially deadly arms race with the Soviet Union, which was thought to be pursuing its own atomic bomb.


Right after the Trinity Test was the Potsdam Conference in Potsdam, Germany. The victors in Europe, consisting of the US, Britain, and the Soviet Union, met to discuss peace in post-war Europe and the ongoing war in Asia and the Pacific. US President Harry S. Truman, who had replaced Franklin D. Roosevelt in April, told Soviet premier Joseph Stalin about the successful Trinity Test, hoping to increase America’s bargaining power. However, it was later revealed that Stalin was well aware of the atomic bomb thanks to the Soviets’ successful espionage efforts.


August 1945: Little Boy & Fat Man

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A photograph of a mushroom cloud resulting from an atomic bomb detonation, via The University of Chicago


After Potsdam, President Truman decided to go forth with the proposed use of the atomic bomb on Japan. An invasion of the home islands of Japan, Operation Downfall, could be catastrophic in terms of casualties. Additionally, the Soviet Union was prepared to declare war on Japan, as per its agreement in late 1943 at the Tehran Conference. A drawn-out conventional war against Japan could result in tremendous American casualties and the taking of Japanese territory by the Soviet Union in their own invasion.


On August 6, 1945, the atomic bomb Little Boy was dropped on Hiroshima, Japan from a B-29 bomber. This single bomb detonated with the force of 15 kilotons of TNT, which resulted in over 100,000 deaths in the city. Despite the shocking force of the explosion, Japan’s government did not respond. Days later, a second bomb was dropped over the city of Nagasaki. Fat Man was more powerful at 21 kilotons and also killed an estimated 100,000 residents of the city.


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A panoramic photograph of the destruction in Hiroshima, Japan caused by the Little Boy atomic bomb, via the National Archives Museum, Washington DC


The world had never seen such destruction caused by a single weapon. Within a one-mile radius of ground zero, almost all buildings were completely destroyed. These included sturdily-built buildings intended to withstand earthquakes. Most houses were seriously damaged up to a mile and a half radius in Hiroshima, and almost two miles in Nagasaki. The intense heat caused by the atomic blast could char wood up to two miles from ground zero, which was often lethal to humans. Damage from the more powerful bomb, Fat Man, was still seen up to four miles from ground zero in Nagasaki.


Six days after the bombing of Nagasaki, on August 15, Japan announced that it would surrender unconditionally. World War II was over. On September 2, Japan’s formal surrender was signed on the battleship USS Missouri in Tokyo harbor.


Post-1945: Nuclear Arms Race

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A map of suspected nuclear warhead amounts by country, via the Federation of American Scientists


The Manhattan Project changed the world forever by significantly furthering nuclear research and developing the weapon that definitively ended World War II. However, the use of the atomic bomb in August 1945 has remained controversial. As critics warned, it did result in a nuclear arms race between the United States and the Soviet Union. On August 29, 1949, the Soviets detonated their first atomic bomb, significantly amplifying the Cold War. Since 1949, several other nations have developed their own nuclear weapons.


The first five nuclear powers became permanent members of the United Nations Security Council, but other nations (India, Pakistan, Israel, and North Korea) have also developed such weapons. As nuclear proliferation continues, however slowly, many wonder if it is only a matter of time before such weapons are used again in warfare. Much diplomatic effort has gone into limiting nuclear proliferation, but efforts of some nations to develop their own nuclear weapons, such as Iran, continue. The controversy over nuclear weapons involves the virtual guarantee that any use of such weapons, which are now up to a thousand times more powerful than those used in 1945, will result in mass civilian casualties. Weapons of mass destruction, which include chemical and biological weapons, cannot be limited to “precision strikes” on military targets. Any use of nuclear weapons, therefore, will kill many innocent civilians.


Will these efforts result in war? Only time will tell.

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By Owen RustMA Economics in progress w/ MPAOwen is a high school teacher and college adjunct in West Texas. He has an MPA degree from the University of Wyoming and is close to completing a Master’s in Finance and Economics from West Texas A&M. He has taught World History, U.S. History, and freshman and sophomore English at the high school level, and Economics, Government, and Sociology at the college level as a dual-credit instructor and adjunct. His interests include Government and Politics, Economics, and Sociology.