Science Section 4

Origins of the Manhattan Project
Europe was in a period of upheaval in the decades following World War I. Adolf Hitler became Chancellor of Germany in 1933, coinciding with his Nazi Party taking control of the German government. Benito Mussolini, having established a Fascist government in Italy, declared himself dictator and forged an alliance with Hitler. Together, Germany and Italy began taking an aggressive stance toward their neighbors while internally establishing policies of racial discrimination and genocide. Germany’s invasion of Poland in September 1939 is generally accepted to be the beginning of World War II in Europe. Meanwhile, a scientific discovery was being made that would alter the course of the war and have tremendous repercussions for the rest of the world. Hahn and Strassman’s discovery of uranium fission in late 1938 made a weapon of unprecedented destructive capability—a so called “atomic bomb”—a theoretical possibility. Within the scientific community, fears began to mount that Hitler or his allies would pursue the development of such a weapon. Many of the scientists actively involved in nuclear fission research, including Enrico Fermi and Hungarian-American physicist Leo Szilárd, had fled the oppressive political environment in Europe.

The Einstein-Szilárd Letter
On August 2, 1939, Szilárd drafted a letter to President Franklin D. Roosevelt warning him about the possibility of Germany initiating research into the uranium chain reaction to create “extremely powerful bombs of a new type.” As the first to conceive of the nuclear chain reaction in 1933, Szilárd was intimately familiar with its potential implications. He recommended that the United States stockpile uranium ore and develop a nuclear research program of its own. In order to attract greater attention to the letter, Szilárd addressed the letter from his friend Albert Einstein and had Einstein sign it.

Why did Einstein sign the Einstein-Szilárd letter?
Einstein, as a German-born Jew, was gravely concerned about the threat posed by Hitler and the Nazi Party. Einstein had been visiting the U.S. when Hitler became chancellor in 1933 and elected not to return upon learning of the persecution sweeping his homeland. Einstein was personally a pacifist and thus morally opposed to the creation or use of weapons. However, he considered the possibility of Germany being first to attain a nuclear arsenal too alarming to ignore.

Roosevelt’s reaction to the Einstein-Szilárd letter
Roosevelt took the letter seriously. He created the Advisory Committee on Uranium, headed by National Bureau of Standards director Lyman Briggs, to review Szilárd’s claims and provide recommendations for government involvement. The November 1, 1939, report authored by the committee recommended that the United States should actively support Fermi and Szilárd’s research into developing a self-sustaining chain reaction and suggested an initial $6,000 purchase of uranium oxide and graphite (around $100,000 in 2015, adjusting for inflation). At the time, the project seemed like a gamble. Although Fermi was certain that a nuclear reactor could be developed, he expressed in 1939 that an atomic bomb seemed unlikely.

As Germany continued to invade neighboring countries in 1940, an American science administrator named Vannevar Bush became increasingly concerned over the lack of coordination between academic researchers and the military. As president of the Carnegie Foundation, Bush had great influence on scientific research policy in the United States. What did Bush propose in a meeting with President Roosevelt? Was his proposal accepted?
In a meeting with President Roosevelt in June 1940, Bush proposed the creation of a National Defense Research Committee (NDRC) to provide oversight of the research and development of the atomic bomb. Roosevelt approved the proposal in less than fifteen minutes, and Bush became chair of the committee.

S-1 Commitee
As NDRC chair, Bush allocated funding for pilot research to explore the mechanics of the chain reaction as well as techniques for enriching uranium to weapons-grade levels. He appointed a subcommittee, codenamed S-1, in charge of improving uranium enrichment techniques. The subcommittee included Ernest O. Lawrence, director of the Radiation Laboratory at the University of California, Berkeley, who took a lead role in advancing the pace of uranium separation research. Lawrence had previously invented the cyclotron, the first particle accelerator, which he converted into a mass spectrometer for separating uranium-235 and uranium-238 isotopes. The primary objective of the S-1 committee was to
produce a critical mass of uranium-235 necessary for an
explosion, although it was unclear at the time whether this amount would be small enough to be carried and deployed by a conventional bomber aircraft. The S-1 committee was tasked with deciding which uranium enrichment method to pursue. Techniques under consideration included gaseous diffusion, centrifuge separation, and electromagnetic separation, although not all of them had been experimentally tested.

How did Great Britain contribute to the Manhattan Project?
Great Britain was already in the process of investigating the critical mass of uranium-235 and developing its own atomic bomb program. Not long after the discovery of nuclear fission, they had estimated the critical mass to be on the order of 10 kg. A representative of the British atomic team, physicist Mark Oliphant, visited the United States in August 1941 to meet with researchers and assess the state of the American bomb project. Oliphant shared key findings with the American researchers, which provided a helpful boost of encouragement.

By late 1941, the atomic bomb appeared to be an achievable goal within a few years, although many challenges remained. At a meeting with President Roosevelt and Vice President Henry Wallace on October 9, 1941, Vannevar Bush summarized the information obtained from the British and discussed the state of the project. What did Roosevelt then instruct Bush to do?
Roosevelt instructed Bush to determine how soon a bomb could be developed and at what cost. Roosevelt also suggested that the United States Army oversee the construction effort, but instructed Bush to confirm the feasibility of the project before entering production.

Pearl Harbor
On December 7, 1941, Japanese fighter planes attacked the American naval base at Pearl Harbor, killing 2,403 people. The following day, the United States dropped its formerly neutral stance in the conflict to declare war on Japan.

With the country now at war, the atomic bomb project took on a new sense of urgency. In March 1942, Bush reported to Roosevelt that Lawrence’s electromagnetic uranium separation using his cyclotron was proceeding successfully. Regarding the bomb project as being more critical than ever, what did Bush suggest? How did Roosevelt respond?
Bush suggested that a bomb could be ready by 1944. In a letter, Roosevelt responded: “I think the whole thing should be pushed not only in regard to development, but also with due regard to time. This is very much of the essence.”

In May 1942, Arthur Compton tasked J. Robert Oppenheimer of the University of California, Berkeley, with what? Who was on the team that Oppenheimer convened? What did they this group confirm/estimate.
Performing neutron calculations for the uranium chain reaction. Oppenheimer convened a team of “luminaries” to assist him with initial calculations for the bomb, including Hans Bethe, John Van Vleck, Edward Teller, Felix Bloch, Emilio Segrè, and Robert Serber. The group confirmed that a fission bomb was possible, although they estimated that twice as much fissionable material would be necessary than was previously thought.

Meanwhile, the S-1 Committee could not settle on a single enrichment process among those being explored. What did they do?
In June 1942, Bush obtained funding for $85 million to construct three different uranium enrichment plants, as well as a fourth to generate plutonium. The United States also began stockpiling uranium ore based on the projected need calculated by the Berkeley team. Uranium oxide was mined domestically in Colorado and imported from deposits in Canada and other locations overseas. At one point, as much as 1,200 tons of imported (unenriched) uranium were being stored on Staten Island.

When did the first successful chain reaction take place? Where? Who initiated this?
Fermi’s first successful self-sustaining chain reaction at the University of Chicago took place on December 2, 1942.

Later December 1942, a select executive group of the S-1 Committee met to finalize plans for the development of the bomb. By the end of the year, Roosevelt had signed off on the proposal, allocating how much money to the effort?
Half a billion dollars to the effort. The project was underway.

With the transition to the production phase, the Army Corps of Engineers assumed control of plant construction and bomb assembly. Where was the Army Office in charge of bomb-development established? When? What did it become known as?
On August 13, 1942, the Army office in charge of bomb development was established in the New York City borough of Manhattan. Informally, the office became known as the Manhattan Engineer District, which would eventually lend the “Manhattan Project” its name.

General Leslie R. Groves
In September 1942, General Leslie R. Groves was selected as the director of the Manhattan Project. As an officer in the Army Corps of Engineers, Groves had extensive administrative experience and several large-scale projects to his name, including the recent construction of the Pentagon. Although he had a reputation for being abrasive and often critical, Groves had a focused, goal-oriented approach that would prove essential to meeting the key deadlines of the Manhattan Project.

Who did Groves select as leader for Project Y? Why was this decision questioned?
Among Groves’ first decisions as director was selecting a leader for Project Y, the weapons development laboratory. Although Ernest Lawrence and Arthur Compton were obvious choices, they could not be removed from their ongoing laboratory work. Compton suggested Oppenheimer, who had led the theoretical team at Berkeley. Impressed by his mastery of a broad range of science and engineering concepts, Groves appointed Oppenheimer. Some within the administration questioned Groves’ choice, as Oppenheimer had not won a Nobel Prize and had limited administrative experience. Furthermore, concerns were raised about Oppenheimer’s affiliation with communist sympathizers, including his wife Kitty and his brother Frank. Nevertheless, Groves was confident in his choice and approved Oppenheimer’s security clearance on July 20, 1943.

Oak Ridge
The primary nuclear enrichment facility for the Manhattan Project was located in rural eastern Tennessee, in a place that would come to be known as Oak Ridge. In October 1942, the Army Corps of Engineers began acquiring over 60,000 acres of land, established in January 1943 as the Clinton Engineer Works. The city of Oak Ridge was later founded to house the tens of thousands of workers employed at the facility. Although Oak Ridge did not exist prior to 1942, by mid-1945 it had already become the fifth-largest city in Tennessee. Oak Ridge housed separate facilities to pursue various methods of enrichment: the X-10 Graphite Reactor, the Y-12 electromagnetic separation plant, and the K-25 gaseous diffusion plant. Although it showed future potential, the centrifuge separation method had encountered technical challenges and was rejected by the S-1 Committee. Construction of the X-10 Graphite Reactor, a pilot plutonium generating reactor, began on February 2, 1943. The X-10 was the second man-made nuclear reactor, after Fermi’s Chicago Pile-1. It began operation on November 4, 1943. The Y-12 plant at Oak Ridge was responsible for electromagnetic separation of uranium isotopes, based on Lawrence’s pilot work with modified cyclotrons at Berkeley. Although electromagnetic separation was not a particularly efficient method of enrichment, it was based on proven technology and thus presented less risk compared to the other methods, which were still under research. The K-25 plant specialized in the gaseous diffusion method. At the time of its construction, the K-25 plant was one of the largest single-roofed buildings in the world. Gaseous diffusion had not yet been experimentally demonstrated and was rushed to production by the S-1 Committee based on its promising theoretical basis. The primary challenge for the technique was designing a barrier that would allow isotopes to separate based upon small differences in their average speed. Although the enrichment level remained relatively low compared to other methods, the yield of gaseous diffusion gradually improved over the course of the Manhattan Project.

Hanford Engineer Wor
Pilot tests by Enrico Fermi at Chicago and the X-10 Reactor at Oak Ridge demonstrated the need for a full-scale reactor to generate fissile plutonium. Recognizing that military resources were already stretched to capacity, Groves pursued industry contracts to support the development of a dedicated plutonium reactor. Groves recruited the DuPont chemical company to oversee the design, construction, and operation of a full-scale plutonium generation plant for the Manhattan Project. DuPont was already a major wartime contractor and possessed considerable organizational strength as well as familiarity with reactor operation. Concerns were raised about constructing an additional nuclear facility at the Oak Ridge site, given its proximity to Knoxville. DuPont explored potential sites in the Pacific Northwest, eventually settling on a site along the Columbia River in Washington. Groundbreaking on the Hanford Engineer Works began in March 1943. The centerpiece of the Hanford site was the B Reactor, the world’s first large-scale plutonium generating reactor. Construction of the B Reactor began in October 1943, and criticality was first achieved in September 1944.

Los Alamos
In 1942, scientists involved with the Manhattan Project were still scattered across universities and laboratories throughout the country. Time was of the essence, and the inability to easily coordinate their research efforts was hampering progress on the bomb design. Project leaders pushed for a centralized location where research scientists could collaborate face-to-face and focus their efforts. Oppenheimer suggested that the laboratory should be in an isolated location for both security and privacy. Groves began scouting locations in northern New Mexico, an area Oppenheimer was familiar with since he owned a ranch in the region. The laboratory was finally constructed in 1943 on the site of the Los Alamos Ranch School, about thirty miles northwest of Santa Fe. Initially referred to as “Site Y,” the location eventually became known as Los Alamos (now Los Alamos National Laboratory). Over the course of the Manhattan Project, the location of Los Alamos was kept a complete secret from the public, its only listed address being a P.O. Box in Santa Fe. As Los Alamos was being constructed in early 1943, Oppenheimer toured the country recruiting top researchers to join the laboratory. Throughout the year, scientists from across the U.S. journeyed to Santa Fe by train to begin work at Los Alamos. Many of the Berkeley “luminaries” joined the staff at Los Alamos, including Hans Bethe and Edward Teller. Several members of the Los Alamos team had already earned a Nobel Prize; others, including Richard Feynman and Emilio Segrè, would become Nobel laureates in later years. Although Albert Einstein had a key role in initiating the Manhattan Project, he never worked directly on the development of the atomic bomb and had no input on its use against Japan. Despite initial concerns about his administrative capability, Oppenheimer provided excellent leadership, meeting the emotional and intellectual needs of his staff while serving as an effective mediator between the military administrators and his fellow scientists. Although they differed widely in personality, Oppenheimer and General Groves formed an effective working relation-
ship that was a significant contributing factor to the success of the Manhattan Project.

Detonation Mechanisms
With the chain reaction relatively well understood, the Los Alamos team concentrated its efforts on designing the bomb mechanism. The fundamental challenge in designing the bomb was rapidly assembling a supercritical mass at the moment of detonation. If two subcritical masses of nuclear fuel are not brought together fast enough, they may produce a smaller explosion and blow apart before the entire material has a chance to fully undergo fission. In this case, the bomb is said to pre-detonate, or “fizzle,” and will not meet its expected yield of explosive energy. Many weapon designs were considered during the initial planning phase of the bomb (Figure 36). Initial work focused on a gun-type plutonium fission device known as “Thin Man” due to its elongated shape (recall Figure 33 from Section III). In April 1944, Los Alamos received the first shipment of plutonium from the Clinton X-10 reactor. Emilio Segrè determined that reactor-bred plutonium contained a higher concentration of plutonium-240 than plutonium created by a cyclotron. Plutonium-240 tended to initiate the chain reaction too quickly, causing a fizzle. This made the gun-type configuration impractical for a plutonium bomb, and research quickly shifted to focus on the implosion method. Mathematician John von Neumann had proposed an implosion-type weapon in September 1943, based on earlier theoretical work by physicist Seth Neddermeyer. The design was technically more complex, but also assembled the critical mass more quickly than the gun design and reduced the risk of pre-detonation. In July 1944, Oppenheimer directed the Los Alamos team to abandon the plutonium gun method in favor of the implosion design. Until that point, the gun method had been viewed as the most efficient pathway to a bomb, and changing course necessitated significant modifications to the project timeline. On August 7, 1944, General Groves reported that an implosion device could be ready by spring 1945 and a uranium gun device by August 1945.

Trinity Test
Due to the complexity of the implosion design, the Los Alamos team opted for a full-scale test in the desert outside Alamogordo, New Mexico. Groves approved the test, under the condition that measures would be taken to recover the expensive nuclear material in the event of a fizzle. Oppenheimer codenamed the test “Trinity,” inspired by the poetry of John Donne. The bomb, nicknamed the “gadget,” had been supplied with plutonium from the Hanford B Reactor. A 100-foot steel tower was constructed to support the bomb, in order to simulate a midair detonation after deployment from an aircraft. (A midair detonation was desirable for maximum destructive power because the bomb would explode spherically outward.) Select teams of observers were stationed in bunkers 10,000 yards north, west, and south of the tower in order to monitor the explosion, measure the energy released, and make damage estimates. At 5:30 am on July 16, 1945, the Trinity test became the first detonation of a nuclear weapon. The test was successful, with an energy release equivalent to about 20,000 tons of TNT. The resulting explosion released a mushroom cloud about 7.5 miles into the air and carved a crater five feet deep and thirty feet across into the ground. The steel support tower had been obliterated. Oppenheimer later said of the mood following the test, “We knew the world would not be the same. A few people laughed, a few people cried, most people were silent.”

How did Truman becoming president affect the Manhattan Project?
On April 12, 1945, Vice President Harry Truman ascended to the presidency following the unexpected death of President Roosevelt. Having served as Vice President for less than three months, Truman had not been made aware of the Manhattan Project and had to be quickly briefed on the extensive progress that had been made toward a weapon of unprecedented destructive power. General Groves and Secretary of War Henry Stimson met with Truman on April 25 to discuss the timeline for testing and deployment of the bomb and its possible use in ending the war.

Position of the Allies when Truman became president
The Allied forces were in a dominant position at the time Truman assumed office. Nazi Germany was under considerable pressure in Europe and finally surrendered to the United States on May 8, 1945. Attention turned to the Pacific front, where Japan was nearing defeat but appeared unwilling to surrender. Japanese cities were under continual attack by American aircraft, and naval blockades interfered with Japanese supply lines, devastating the local economy.

In spring 1945, what did the Allies begin preparing for? What was the downside to this?
An eventual invasion of Japan. Such an operation was expected to be extremely costly for both sides. The geography of Japan made it relatively easy for the Japanese to anticipate and defend against any Allied invasion attempts. Consequently, estimates placed the expected Allied casualties in the millions, with as many as ten million casualties expected for the Japanese. Nonetheless, a coordinated invasion by the American and British forces was tentatively scheduled for November 1.

The atomic bomb remained a closely guarded secret, known only to top officials within the Manhattan Project and the Truman administration. How did the Manhattan Project affect Truman’s negotiations with Japan?
The successful Trinity test on July 16 strengthened Truman’s hand as he negotiated with Japan over terms for ending the war. On July 26, the Allied leaders presented terms of surrender to the Japanese government in the Postdam Declaration. Japan rejected the terms a few days later, setting the stage for the first military use of the bomb.

Over the course of the Manhattan Project, a number of scientists became uncomfortable with the proposed military use of the atomic bomb. What did they do in response?
In July 1945, Leo Szilárd circulated a petition addressed to President Truman, calling upon him to reconsider any use of the bomb against Japanese civilians. Szilárd’s petition was signed by seventy Manhattan Project scientists. However, unsympathetic members of the Truman administration, including incoming Secretary of State James Byrnes, prevented the petition from reaching the president’s desk.

Ernest Lawrence also suggested a non-military demonstration of the bomb’s destructive capability to the Japanese as a means of compelling their surrender. What were some arguments against this?
Arguments against a demonstration included:
1. The atomic bomb represented entirely new technology and was still being tested. A technical failure would embarrass the United States and potentially make the Japanese less likely to surrender.
2. Only two bombs had been produced, the product of several years of labor and billions of dollars.
3. A demonstration would remove the element of surprise, enabling Japan to undertake measures to counteract the effective use of the bomb (such as by relocating American POWs to anticipated bombing targets). The Scientific Advisory Panel ultimately rejected any demonstration, stating “we can propose no technical demonstration likely to bring an end to the war; we see no acceptable alternative to direct military use.”

The selection of targets for the atomic bomb
The selection of targets took place over the course of summer 1945. Hiroshima, a major port and location of military headquarters, was selected as a strategic target. Furthermore, Hiroshima had thus far not been a target of air raids, allowing the effect of the bomb to be more clearly measured. Kokura and Yokohama, both centers of manufacturing, were also possible targets. Kyoto, the former capital and a major industrial center, was briefly considered but omitted due to its historical significance. Nagasaki, a critical seaport and industrial center, was added to the target list in place of Kyoto.

The bombing of Hiroshima
The bombing of Hiroshima took place on August 6, 1945. The bomb, codenamed “Little Boy,” was a gun-type uranium weapon. The bomb leveled five square miles of the city, exploding with the equivalent energy of about 15,000 tons of TNT. An estimated 140,000 people were killed. (This estimate includes both immediate and near-term deaths resulting from the bomb.) The heat from the blast generated firestorms that swept through the areas that were left standing by the explosion. The intense flash of radiation burned permanent shadows of people and objects on the walls of buildings, and scorched clothing patterns into victims’ skin. As upwards of ninety percent of medical personnel were killed or disabled in the initial blast, many victims were unable to receive treatment and succumbed to the effects of intense radiation exposure. Within hours of the bombing, President Truman released a statement by radio informing the American public that he had authorized the detonation of an atomic bomb “in order to shorten the agony of war.” He called upon Japan to accept the terms of surrender, and threatened a subsequent attack of equal magnitude if they did not comply. After the Japanese government and Emperor Hirohito made no indication of initiating a surrender attempt, the U.S. prepared for a second bombing.

The bombing of Nagasaki
On August 9, a second atomic bomb, codenamed “Fat Man,” was dropped on the city of Nagasaki. Fat Man was an implosion-type plutonium bomb, the same design that was used in the Trinity test. The blast was even more powerful than Little Boy, representing the equivalent of 21,000 tons of TNT. However, local geography constrained the destruction to three square miles, resulting in fewer casualties than had occurred in Hiroshima. Approximately 74,000 people were killed by the bomb. (Again, this estimate includes both immediate and near-term deaths resulting from the bomb.)

Japanese surrender
On August 15, Japan announced its surrender to the Allied forces. The formal surrender took place on September 2, 1945, on the deck of the U.S.S. Missouri. The most destructive war in human history had been ended with the most destructive weapon yet created by man.

The affect of the Manhattan Project after the war
By the end of the war, the Manhattan Project employed more than 130,000 people, and its total budget amounted to almost $2 billion (equivalent to almost $26 billion in 2015). By 1945, the workforce and infrastructure encompassed by the project was comparable in size to the American automobile industry. Secrecy was of the utmost importance at every stage of the operation; many employees only discovered the true purpose of the project with the announcement of the bombing of Hiroshima. The Manhattan Project represented an unprecedented coordinated effort between the government, industry, civilian scientists, and the military. In 1939, few could have predicted the project would be successful in translating still-recent discoveries within the field of nuclear physics into a fully functional weapon. The Manhattan Project not only cemented a role for scientific research in national defense, but it also left in place a network of national laboratories at Los Alamos, Oak Ridge, and other sites that still conduct federally-funded research to this day. The combination of federal funding and facilities enabled a new model for large-scale research, later termed “Big Science” by Alvin Weinberg, the director of Oak Ridge National Laboratory.

The Atomic Energy Commission
A major question remained after the end of the war: should the U.S. military remain in control of the atomic energy program during peacetime? In October 1945, Congress deliberated over the May-Johnson Bill, which would effectively continue military authority over the program. Although several Manhattan Project scientists, including Fermi and Oppenheimer, issued lukewarm support of the bill, others such as Leo Szilárd vehemently opposed the military’s continued administration of the program. Waning support for the May-Johnson Bill led to the introduction of the alternative McMahon Bill in
December 1945, which placed authority in civilian rather than military hands. President Truman signed a version of this bill into law as the Atomic Energy Act of 1946. Under the provisions of the law, authority over the atomic program was officially transferred from the United States Army to the United States Atomic Energy Commission (AEC) on January 1, 1947. The AEC was a five-member civilian board aided by a general advisory committee and military liaisons. The AEC subsequently established the National Laboratory system and instituted continued nuclear testing to expand the United States’ nuclear arsenal. In 1974, the AEC was effectively abolished, and its duties were reassigned to other agencies, including the Nuclear Regulatory Commission and the Energy Research and Development Administration. In 1977, President Jimmy Carter signed a law establishing the United States Department of Energy, which now oversees and regulates the nation’s nuclear weapons program and nuclear energy production.

The Atomic Age
William Laurence, a New York Times journalist who had witnessed both the Trinity test and the bombing of Nagasaki, coined the term “Atomic Age” to describe the postwar era, in which atomic energy was expected to play a large role. Reporters made numerous bold predictions about the fantastic ways in which atomic power would transform everyday life. Atomic energy was heralded as a nearly limitless source of power, with Lewis Strauss predicting that it would make electricity “too cheap to meter.” Meanwhile, citizens read newspaper and magazine articles predicting “atomic cars” and “atomic medicine” to be just around the corner. A number of Manhattan Project scientists sought to inform the public about the dangers of nuclear weapons and promote peaceful applications atomic energy. In 1946, Albert Einstein founded the Emergency Committee of Atomic Scientists (ECAS) to support nuclear disarmament and world peace. Members of the ECAS included Leo Szilárd and Hans Bethe, who directly served on the Manhattan Project. The Committee conducted speaking tours and published materials to promote their peaceful message. In 1945, another Manhattan Project scientist, Eugene Rabinowitch, co-founded the Bulletin of the Atomic Scientists, a non-technical magazine on nuclear weapons and global security. The Bulletin continues to serve as a reference on global issues that is accessible to scientists and citizens alike. In 1947, the Bulletin created the Doomsday Clock as a symbol of the threat posed by nuclear devastation. The closer the Clock is set to midnight, the more pressing the threat of global devastation. At the time of its creation, the Clock read seven minutes
to midnight; it has since been set as close as two minutes and as far away as seventeen minutes. As of January 2016, the Clock is set to three minutes to midnight.

The Cold War and the Arms Race
The United States and the Soviet Union emerged from World War II as rival superpowers. Although many American experts predicted the Soviet Union would not develop nuclear weapons until the mid-1950s, the Soviets shocked the world by detonating their own nuclear weapon on August 29, 1949. The subsequent decades-long competition between the U.S. and the Soviet Union to expand their nuclear arsenals became a major element
of the Cold War. Consequently, the persistent threat of nuclear attack permeated the public consciousness, with many U.S. school children participating in drills to “duck and cover” under their desks in the event of such an attack. Thermonuclear weapons, which had been theorized by Edward Teller and others during th Manhattan Project, represented the next step in the race for more powerful nuclear weapons. Oppenheimer publicly opposed the development of hydrogen bomb, but was ignored. The United States detonated the first hydrogen bomb on November 1, 1952, on an atoll in the Pacific Ocean. Less than a year later, the Soviet Union detonated a thermonuclear device of its own in August 1953.With the eventual capability to launch nuclear warheads overseas, the two nations balanced tensely on the notion that any attack would be met with retaliation—a scenario often called “mutually assured destruction,” known by the acronym MAD. The highly politicized postwar climate exposed rifts and a sense of regret within the scientific community. Many of the scientists who had supported the Manhattan Project had done so to beat Nazi Germany to the bomb, only to discover after the war that the Germans had explored, but not forcefully pursued, the development of a nuclear weapon. Albert Einstein also expressed deep regret over his role in initiating the Manhattan Project. In 1947, Einstein was quoted by Newsweek as saying, “had I known that the Germans would not succeed in developing an atomic bomb, I would have done nothing.” Oppenheimer became distraught over the destructive outcome of the Manhattan Project, commenting to President Truman, “I feel I have blood on my hands.” Oppenheimer pushed for an international authority to regulate the use of atomic energy, an effort that stalled in the United Nations as neither the U.S. nor the U.S.S.R. were willing to relinquish control of their arsenals. Supporters of nuclear disarmament were often blacklisted and investigated for suspicious activities or communist associations. For his opposition to the development of the hydrogen bomb, Oppenheimer became a
high-profile target of Lewis Strauss, commissioner of the AEC, who sought to discredit Oppenheimer and block the renewal of his security clearance. Following a month-long series of hearings, during which a number of his former colleagues provided testimony on both sides, Oppenheimer’s security clearance was revoked.

Atoms for Peace
On December 8, 1953, President Dwight D. Eisenhower delivered an address to the United Nations General Assembly entitled “Atoms for Peace,” in which he outlined a commitment to peaceful applications of nuclear energy. The following year, Eisenhower signed the Atomic Energy Act of 1954 into law, which loosened provisions of the 1946 Act in order to permit the development of civilian use of nuclear power plants. On July 27, 1957, the UN established the International Atomic Energy Agency (IAEA) to promote the peaceful use of atomic energy and provide safeguards against the misuse or weaponization of nuclear material. Besides the United States and the Soviet Union, three other nations developed nuclear weapons during the 1950s and ’60s: the United Kingdom, France, and China. However, the U.S. and U.S.S.R. maintained the largest nuclear arsenals by far. On July 1, 1968, the United States joined sixty-one other nations, including the Soviet Union, in signing the Nuclear Non-Proliferation Treaty, which prevented the acquisition of nuclear weapons by any nation that did not already possess them. President Carter signed the Nuclear Non-Proliferation Act of 1978 into law, which outlined strategies for preventing the spread of nuclear materials for weapons-related use, while allowing foreign nations access to such materials for peaceful use. In recent years, nuclear proliferation has become a pressing global security issue. Various diplomatic strategies are being employed to ensure that nations can benefit from the advantages of nuclear power without posing a threat to the rest of the world.