The U.S. program to develop nuclear weapons, codenamed the Manhattan Project, formally began on August 13, 1942. By bringing together the world’s top scientific minds and leveraging the nation’s powerful industrial capabilities, the project succeeded in creating the world’s first atomic weapons in less than three years. Ultimately, on August 6, 1945, under President Harry Truman, the United States dropped the “Little Boy” atomic bomb on Hiroshima, followed by the “Fat Man” bomb on Nagasaki on August 9. This devastating act hastened Japan’s surrender, bringing an end to the bloody conflicts and upheavals of World War II. Here are some lesser-known facts about this pivotal scientific achievement. More on manhattanyes.com.
Inspired by Albert Einstein
The project’s origins date back to 1939, the year World War II began. German-born genius Albert Einstein, along with Leo Szilard and other physicists, wrote a letter to U.S. President Franklin D. Roosevelt. In it, they expressed fears that Adolf Hitler was developing a new weapon of mass destruction using uranium. Alarmed U.S. officials decided to get ahead of the Nazi dictator and convened the world’s leading physicists for the secret Manhattan Project. Initially, its headquarters were located in Manhattan, New York City, hence the name.
Retaliation for Pearl Harbor
In 1939, the United States found itself largely unprepared for war. The American army was small and poorly equipped. Everything changed after Japan’s attack on December 7, 1941, on Pearl Harbor – the central base of the U.S. Pacific Fleet. The goal was to neutralize the American fleet, ensuring freedom of action for the Japanese army and navy in Southeast Asia. This attack compelled the States to officially enter World War II, joining Great Britain, China, and the USSR in the Allied coalition. The nuclear attack on Japanese cities was, for some, seen as retaliation for Pearl Harbor. However, while approximately 2,300 American military personnel died at Pearl Harbor, the bombings instantly claimed the lives of an estimated 70,000 residents in Hiroshima and 60,000 in Nagasaki. Furthermore, between August and December 1945, about half a million more people in both cities died from injuries and radiation-induced illnesses.
A Model for the Soviet Union
The strictest secrecy was maintained within the Manhattan Project. Intelligence officers and the FBI did everything possible to prevent Nazi Germany or Japan from learning about the developments. Although the USSR was an ally of the U.S., American officials sought to prevent any other country from benefiting from their research. Nevertheless, Soviet intelligence managed to obtain technical information that Soviet scientists later used to create their own weapons. It all began when Soviet intelligence noticed British and American journalists writing extensively about nuclear fission. One of the most famous spies was Klaus Fuchs, a German physicist who secretly pledged allegiance to the USSR. He was assigned to the Los Alamos National Laboratory, where he worked on American bomb research and development. Fuchs passed information to the USSR and was eventually caught after the war, candidly confessing to his actions. Interestingly, Manhattan Project scientists also utilized the British-Canadian atomic bomb program (Project Tube Alloys). Despite promises to share research, the U.S. did not provide full information to Britain and Canada. It took Britain another seven years to successfully test its own nuclear weapon. Incidentally, although Germany was the first country to discover nuclear fission and began research in April 1939, its program never achieved its goal due to a lack of state support and Nazi discrimination against minorities, which led many prominent scientists to flee the country.
Nearly $2 Billion from the Budget
Over 130,000 people were involved in the Manhattan Project. It cost the country nearly $2 billion (equivalent to approximately $22 billion today).
Key Research Hub
The Los Alamos National Laboratory in New Mexico was the project’s most critical research center. Established in January 1943, it not only developed nuclear weapons but also functioned as an intelligence analysis agency. Based on gathered data, the laboratory conducted applied research and analyzed the Soviet nuclear program and arsenal, as well as similar programs in other socialist countries. J. Robert Oppenheimer, an American theoretical physicist and nuclear physicist, led the laboratory. He is widely known as the director of the Manhattan Project and is often called the “father of the atomic bomb.”
Primary Manufacturing Hub
While Los Alamos, New Mexico, served as the main laboratory for bomb research and design, Oak Ridge, Tennessee, was the primary production center. Enriched uranium, essential for nuclear weapons, was produced there. Major General Leslie Groves, the military head of the Manhattan Project, favored Oak Ridge for several reasons. Its relatively small population made land acquisition affordable (all residents were evicted). It was accessible by road and rail, and utilities like water and electricity were available thanks to a recently completed dam. A 17-mile-long (approximately 27 km) valley was allocated for the project, surrounded by ridges that offered natural protection against any potential disasters spreading to nearby facilities.
24 Tragic Incidents
During the Manhattan Project, 24 employees died. Many of these deaths were due to construction accidents. However, scientists Harry Daghlian and Louis Slotin met an even grimmer fate. On August 21, 1945, Daghlian accidentally dropped a tungsten carbide brick onto a plutonium core assembly, causing the core to go supercritical. He quickly removed the brick but received a fatal dose of radiation and died in agony about a month later. On May 21, 1946, Slotin was using a screwdriver to hold the upper part of a beryllium neutron reflector above a core assembly. His screwdriver slipped, and the hemisphere fell onto the core, causing a lethal burst of radiation and a flash of blue light. Slotin quickly knocked the upper reflector part away from the core and onto the floor, neutralizing the immediate criticality. However, this didn’t save him; the scientist died from acute radiation poisoning nine days later.
The First Detonation: July 16, 1945
The world’s first atomic bomb test, codenamed “Trinity,” took place on July 16, 1945, in the New Mexico desert. The “Fat Man” bomb dropped on Nagasaki was of the same design. Predictions for the Trinity test’s yield ranged from a complete dud (zero power) to 18 kilotons of TNT equivalent, and some even feared the destruction of New Mexico or the entire planet due to a runaway atmospheric chain reaction. Ultimately, physicist Isidor Rabi’s prediction of a 21-kiloton yield proved accurate. After the successful test, Oppenheimer famously quoted the Hindu scripture, the Bhagavad Gita: “Now I am become Death, the destroyer of worlds.”
The Two Bombs Worked Differently
“Little Boy” and “Fat Man,” the bombs dropped on Hiroshima and Nagasaki, operated on different principles. “Little Boy” relied on the fission of uranium-235, while “Fat Man” used the fission of plutonium. In general, all atomic bombs are based on a chain reaction that releases immense thermal energy. This occurs when a neutron strikes the nucleus of a uranium-235 or plutonium isotope, splitting the atom.