Dawning of the Nuclear Age

O n Monday, July 16, 1945, at exactly 5:29:45 a.m. Mountain War Time, the world's first successful detonation, or explosion, of an atomic bomb occurred. Referred to by scientists as "the gadget" or "the thing," it exploded with the force of 21,000 tons (19,047 metric tons) of TNT (a commonly used high explosive). A flash of light brighter than people had ever witnessed before illuminated the landscape of the test site near Alamogordo, New Mexico, in an area called Jornada del Muerto (commonly translated as Journey of the Dead). The code name for the test was "Trinity."

As noted on the Los Alamos National Laboratory Web site, General Leslie R. Groves (1896–1970), the U.S. Army officer in charge, later recalled, "As we approached the final minute the quiet grew more intense. As I lay there in the final seconds, I thought only what I would do if the countdown got to zero and nothing happened." Later, General Thomas Farrell, deputy to Groves, wrote that the "whole country was lighted by a searing light with the intensity many times that of the midday sun. It was golden, purple, violet, gray and blue. It lighted every peak, crevasse and ridge of the nearby mountain range with a clarity and beauty that cannot be described but must be seen to be imagined. Seconds after the explosion came first the air blast pressing hard against the people, to be followed almost immediately by the strong sustained awesome roar that warned of doomsday and made us feel we puny things were blasphemous [showing a lack of reverence] to dare tamper with the forces heretofore [previously] reserved for the Almighty." The world's first successful detonation of an atomic bomb was the climax of a secret effort known as the Manhattan Project.

The Manhattan Project began during 1942 in the middle of World War II (1939–45). The goal of the project was to build an atomic weapon before scientists in Germany or Japan did. The United States was at war with these two nations. During the 1930s, scientists in both the United States and Germany greatly expanded knowledge in the field of nuclear physics, the study of the structure and reactions of an atom. Late in 1938, nuclear physicists in Germany discovered nuclear fission. Fission is the splitting of the nucleus of an atom; when the nucleus is split, a substantial amount of energy is released. Aware of this discovery, German physicists who had left Germany to live and work in the United States, due to Adolf Hitler (1889–1945) and his politics of Nazism (which stressed racism), feared the Germans could and would build powerful atomic bombs.

Albert Einstein's letter

Three Hungarian scientists who lived in Germany and then moved to the United States—Leo Szilard (1898–1964), Edward Teller (1908–2003), and Eugene Wigner (1902–1995)—asked the German-born Albert Einstein (1879–1955), America's most famous physicist, to write a letter to U.S. president Franklin D. Roosevelt (1882–1945; served 1933–45) expressing their fears and stressing the urgency of the atomic bomb situation. As noted on the Manhattan Project Heritage Preservation Association Web site, Einstein penned his letter on August 2, 1939, stating that recent breakthroughs in nuclear research led him to believe "the element uranium may be turned into a new and important source of energy in the immediate future" and that "extremely powerful bombs [could be] constructed." Einstein requested increased funding for American nuclear physicists working throughout the country in university laboratories and urged better communication among them. Realizing

that Germany's Hitler could develop these powerful new weapons and use them to hold the world hostage, Roosevelt established the Uranium Committee in October 1939. This was the first step toward organized development of an atomic bomb (A-bomb) in the United States.

Long-distance difficulties

Across the country, many institutes of advanced learning (including the University of California's Radiation Laboratory and the physics departments at Columbia, Stanford, and Cornell Universities; the California Institute of Technology; and the Universities of Wisconsin and Illinois) stepped up research into preparing nuclear materials such as uranium-235 and plutonium. Uranium-235 and plutonium are fissionable elements and the bases of atomic bombs. The National Academy of Sciences announced that its number one priority was to build atomic weapons before anyone else in the world did so. Scientists met at conferences to share their knowledge, but coordinating the scattered research projects proved problematic. Long-distance communication between scientists was all but impossible because government security regulations required that uranium and plutonium research be kept top-secret; scientists could not discuss their research over the phone or in writing. By the fall of 1942, a research facility in one location, where key scientists could speak in person and work together, was desperately needed.

The Manhattan Project

Vannevar Bush (1890–1974) was head of the Office of Scientific Research and Development (OSRD), the wartime civilian scientific mobilization group. He asked President Roosevelt to assign to the military the construction of a lab and production plants. Roosevelt assigned the army to work with OSRD. In September 1942, Leslie R. Groves of the Army Corps of Engineers was appointed to take charge of the weapons program. Groves was immediately promoted to brigadier general so that he would have sufficient rank to impress the senior civilian scientists in the project. Groves and the Manhattan Engineer District, headquartered in New York City, took charge. Groves named the weapons program the Manhattan Project after his home base. With directness and determined efficiency, Groves established two large production plants, the Clinton Engineer Works in Oak Ridge, Tennessee, and the Hanford Engineer Works in eastern Washington State. Oak Ridge would produce uranium-235; Hanford would produce plutonium. Construction of a third facility, the Manhattan Engineer District Laboratory, began in March 1943 in a remote desert area near Los Alamos, New Mexico. The first atomic bomb would be assembled at the Los Alamos site, dubbed Project Y, about a hundred miles north of Albuquerque.

In October 1942, Groves named J. Robert Oppenheimer (1904–1967), a theoretical physicist from the University of California at Berkeley, to lead the laboratory's scientists. In March 1943, before construction of the facility was anywhere near complete, the most renowned scientists in the country and their families began arriving at Los Alamos. Navigating primitive roads and dealing with inadequate cooking and sleeping accommodations, they began their work. No one knew how close the Germans were to completing a bomb, but if Germany won the bomb race, America would lose the war. Every month, week, and day counted.

A secret project, a secret town

Everything about the Manhattan Project was top-secret. When Robert Serber (1909–1997) of the University of Illinois, Oppenheimer's chief theoretical assistant, rose to give one of the first lectures to the gathered Los Alamos scientists, he announced that the project objective was to build a practical military weapon, a bomb based on nuclear fission. Upon hearing the word bomb, Oppenheimer sent a note up to the podium saying Serber should use the term "gadget," not bomb, because many carpenters and other workers were still present and might overhear. From then on, the bomb was always referred to as "the gadget."

Within the year, thousands of personnel from all over the country had arrived, and Los Alamos became a small town. Everyone there had passed rigorous background checks. The name Los Alamos could not appear on any letters or parcels, incoming or outgoing. Instead the address was Box 1663, Santa Fe, New Mexico. The address on the birth certificates of babies born at the Los Alamos Engineers Hospital between 1942 and 1945 was simply "Box 1663."

Ultimately about 140,000 military and civilian individuals—physicists, chemists, engineers, teachers, carpenters, janitors, etc.—worked on the Manhattan Project at Los Alamos and in various secret locations throughout the United States. However, only a tiny percentage ever knew the ultimate goal was to build an atomic bomb.

Mission completed

On July 16, 1945, the "gadget" tested successfully. At that point, the United States had the only workable atomic bomb in the world. Los Alamos engineers did not realize that the German attempt to develop a bomb had been derailed years earlier. Lack of organization, then the devastation of World War II, had prevented any concerted effort by the scientists in Germany.

Los Alamos produced two bombs, code-named "Little Boy" and "Fat Man." Confident that Little Boy would work, scientists assembled the uranium-235-based bomb and readied it for shipment in early July 1945. Fat Man, which had a plutonium base, needed to be tested to confirm that it would detonate. The "Trinity" test near Alamogordo, New Mexico, was therefore a test of a plutonium-based bomb like Fat Man. When that bomb detonated, American scientists knew they had opened the age of nuclear weaponry; they also knew that this weapon would end World War II.

World War II ends

The results of the Trinity test were immediately conveyed to U.S. president Harry S. Truman (1884–1972; served 1945–53), who had taken office after President Roosevelt's death in April 1945. Truman was attending a conference in Potsdam, near Berlin, Germany. He casually informed Soviet premier Joseph Stalin (1879–1953), also in attendance, that the United States had a new weapon of great destructive power. On July 26, 1945, Truman and Clement Attlee (1883–1967), who had replaced Winston Churchill (1874–1965) as Great Britain's prime minister, issued an ultimatum to Japan: Surrender or face total destruction. Japan rejected the ultimatum.

In the early-morning hours of August 6, Little Boy rode in the belly of a U.S. B-29 bomber, the Enola Gay, that was part of the 509th Composite Air Group, stationed in the Mariana Islands in the western Pacific Ocean. At precisely 8:16:02 a.m. Japanese time, Little Boy was dropped on the center of Hiroshima, Japan, instantly killing at least 80,000 people and seriously injuring at least 100,000 more. Many of the injured would die of burns and radiation exposure. Japan did not surrender. On August 9, at 11:02 a.m. Japanese time, Fat Man was dropped on Nagasaki, Japan, killing nearly 74,000 and injuring 75,000 of Nagasaki's 286,000 residents. Japan agreed to surrender on August 14, 1945.

Arms race begins

When President Truman mentioned to Stalin at Potsdam that the United States had a powerful new weapon, he did not realize that Stalin was already aware of the Manhattan Project; Soviet spies had been reporting to Stalin regularly. American officials no doubt hoped that U.S. possession of an atomic bomb would give them an advantage in postwar negotiations and make Stalin and the Soviets more manageable. Instead, Stalin accelerated the Soviet A-bomb effort. The Soviets vowed to produce their own atomic weapons and to break the U.S. monopoly as soon as possible. The Soviet Union and the United States were now locked in an arms race, with each side trying to equal or outdo the military strength of the other. This further promoted the "cold war" between the two countries: Neither could use its weapons without risking annihilation, but both continued the battle by building more powerful bombs.

"Joe-1"

Only a few weeks after the bombing of Hiroshima and Nagasaki, Stalin ordered forty-two-year-old Igor Kurchatov (1903–1960), the Soviet Union's premier nuclear physicist, to build an atomic bomb by 1948. The focus of the Soviet nuclear program was to detonate a nuclear bomb as soon as possible, no matter the cost. Stalin also selected Lavrenty Beria (1899–1953), leader of the dreaded Soviet secret police, to organize and manage the Soviet bomb project. Kurchatov had the same role in the Soviet program as Oppenheimer had had in the Manhattan Project. Beria was the Soviet counterpart to General Groves—with one major distinction: Apparently Beria had permission to shoot Kurchatov and his staff if they failed at their task. Beria was fond of announcing to Kurchatov, "You will become camp dust." Perhaps partly out of fear but overwhelmingly out of a sense of patriotic duty to his country that had been so injured by the Germans during World War II, Kurchatov set about his task immediately. Like most Soviets, he believed the United States intended to use its atomic power to gain influence around the world, perhaps to push its economic and political views onto the Soviet Union and its allies.

Both Kurchatov and Beria were talented organizers. They mobilized people and resources. Uranium was mined; a nuclear reactor (a device in which nuclear reactions took place) was built; and the super-secret atomic weapons laboratory, Arzamas-16, took shape. It was nicknamed "Los Arzamas, " a play on words with the U.S. atomic weapons laboratory site of Los Alamos. Arzamas-16 was much like Los Alamos: It was developed at the site of a small town, Sarov. About 250 miles (400 kilometers) east of Moscow, Sarov soon disappeared from maps. All the great Soviet scientists would live and work at this top-secret location, and after several years, they created a plutonium bomb, code-named "Joe-1."

In early 1946, a two-story house called the "Forester's Cabin" was built at Los Arzamas for Kurchatov and his wife, Marina. It was within walking distance of Kurchatov's lab. Kurchatov was likable and capable—he even coped well with Beria—and he brought about intense loyalty from his fellow scientists. He often sat at a table with his staff, surrounded by the extensive flower and vegetable garden he had planted at his house, and invited them to discuss problems and working plans. At the end of the discussion, Kurchatov would assign a month's worth of work and send them back to the lab. Then, only hours later, he would head down his path through the woods to the lab to see how much progress had been made.

After a series of technical delays, Kurchatov delivered on August 29, 1949. The Soviets' first atomic test, code-named "First Lightning," was successful. A plutonium bomb named Joe-1, which closely resembled the U.S. "gadget" Fat Man, detonated at the Semipalatinsk Test Site in northeastern Kazakhstan. A few days later, the United States became aware of the test. A U.S. Air Force B-29 on a weather mission over the North Pacific encountered a very high radioactivity count. Analyzing the data, U.S. scientists realized the Soviets had detonated a plutonium atomic bomb.

"Enormous"

U.S. intelligence had figured that the earliest possible Soviet completion of a nuclear weapon would be about 1953. It seemed reasonable that Kurchatov and his scientists would need that much time to design and build their own atomic bomb. However, the Soviet project had been speeded up by information from "atomic spies" within the Manhattan Project. "Enormous" was the code word the atomic spies used to refer to the Manhattan Project. Between 1943 and 1945, Klaus Fuchs (1911–1988), Theodore Alvin Hall (1925–1999),

David Greenglass (1922–), Ruth Greenglass (1925–), Julius Rosenberg (1918–1953), Ethel Rosenberg (1915–1953), and Harry Gold (c. 1911–1972) helped deliver technical information from the Manhattan Project to Beria and Kurchatov and their colleagues at Los Arzamas. Fuchs, a Los Alamos scientist; Hall, a Los Alamos physicist; and David Greenglass, a Los Alamos machinist, passed detailed information to the Rosenbergs and Gold. In turn, the information was passed on to the Soviets. In retrospect, historians believe the information that the spies passed on speeded up Soviet atomic bomb development by one to two years.

On September 23, 1949, a shocked United States listened as President Truman revealed information about the Soviet atomic blast. Americans absorbed the news with dread rather than panic. Clearly the Soviets had caught up. Americans now questioned their own safety. Fuchs had sent detailed data about the American plutonium bomb, "Fat Man"; that explained Joe-1's resemblance. Hall was the only atomic spy U.S. officials knew about who was not caught.

The Strategic Air Command and the Atomic Energy Commission

After the initial race to create an atomic bomb, two key groups came into being in the United States in 1946: the Strategic Air Command and the Atomic Energy Commission. The U.S. military established the Strategic Air Command (SAC), and by the late 1940s SAC's goal was to identify targets in the Soviet Union and be ready to deliver nuclear weapons to those targets. It was hoped that this would deter any Soviet aggression. The United States saw atomic weapons as a way to match the strength of the Soviet land armies in Eastern Europe.

The Atomic Energy Commission (AEC), established by Congress in July 1946, took over management of the nuclear research facilities at Oak Ridge, Hanford, and Los Alamos. Universities contracted with the AEC for research and development of weapons. The University of California contracted with the AEC to manage Los Alamos. Although World War II had ended, the United States and the Soviet Union were becoming entangled in a war over political and economic ideas—the Cold War. Increasingly, Americans believed that the United States needed to maintain superiority in weaponry to deter Soviet aggression. Subscribing to this view, the AEC favored development of weapons rather than pursuing ways to peacefully take advantage of nuclear energy.

Hydrogen bomb

President Truman shocked the United States and the world with his announcement that the Soviet Union had successfully detonated an atomic weapon. The United States had to reassess its position in the world: U.S. leaders were already worried about the strong and growing Soviet communist influence in Eastern Europe. Additionally the communists controlled China. Many Americans believed that only being on constant alert and having a strong military armed with nuclear weapons could keep the Soviets in check. Indeed, some feared a communist takeover of the United States if the United States let down its guard, even momentarily.

In the fall of 1949, after the Soviet atomic bomb test, a secret and heated debate raged among American government officials, scientists, and the U.S. military. Reevaluating U.S. strength in light of the Soviet atomic test, Truman turned first to the AEC. After completing the Manhattan Project, U.S. scientists had considered the development of a hydrogen bomb (H-bomb), which would be far more destructive than the bombs dropped in Japan. They knew that H-bombs could be created through fusion, or joining together, of the atomic nuclei of the element hydrogen. However, AEC director David Lilienthal (1899–1981) did not support further testing in peace time.

Because the Soviets had just developed their own A-bomb, others on the AEC wanted the United States to do immediate and concentrated research to develop the H-bomb. Lilienthal, fully aware of the H-bomb's boundless destructive power, still resisted. He then asked for direction from the AEC's General Advisory Committee (GAC), a group made up of scientists including Manhattan Project leader J. Robert Oppenheimer. The GAC supported Lilienthal, recommending a buildup of A-bombs but rejecting development of the H-bomb.

However, yet another group of scientists (including Edward Teller, who in 1939 had urged Einstein to write to then-President Roosevelt about development of the A-bomb) argued in favor of the H-bomb. Concurring, the U.S. military strongly urged development, emphasizing the need to produce such a weapon before the Soviets could produce one. President Truman managed to keep all the debate secret; he hoped the press and the American public would not hear about the H-bomb before he had decided what to do. He next appointed a three-man committee—Lilienthal, Secretary of State Dean Acheson (1893–1971), and Secretary of Defense Louis Johnson (1891–1966)—to debate the issue and advise him. Lilienthal remained opposed, but Acheson and Johnson supported development of the H-bomb. Truman believed that negotiating a mutual agreement with the Soviets not to pursue the H-bomb was hopeless, so in late January 1950 he announced to the American public that development would proceed on all types of nuclear weapons, including the H-bomb. Scientists at Los Alamos immediately began work on the H-bomb.

By the late 1940s, Soviet scientists knew that U.S. scientists were researching the H-bomb, so they began research, too. The Soviet investigation team was headed by physicist Yakov Zel'dovich (1914–1987) and included fellow physicists Andrey Sakharov (1921–1989), Vitali Ginzburg (1916–), and Viktor Davidenko. Sakharov would become known as the father of the Soviet hydrogen bomb.

Thermonuclear race

On November 1, 1952, from the tiny atoll, or coral island, of Enewetak, part of the western Pacific's Marshall Islands, a fireball arose. America's first hydrogen bomb had been detonated. The fireball's mushroom shape grew to 100 miles (160 kilometers) in diameter and rained down radioactive material. The H-bomb was 800 times more powerful than the A-bomb dropped on Hiroshima, exploding with a force of 10.4 megatons (9,432,800 metric tons) of TNT. The bomb could not be transported by aircraft; it was too heavy and had to be cooled by refrigeration until detonated.

On August 12, 1953, the Soviets successfully tested Joe-4 at Semipalatinsk Test Site. Although much smaller than the U.S. test bomb and not a true hydrogen bomb, Joe-4 brought the Soviets into the race. On March 1, 1954, the United States detonated a physically smaller, lithium-based hydrogen bomb that could be carried by a B-47 jet bomber. The test, known as "Bravo," occurred at the Bikini Atoll, 200 miles (321 kilometers) from Enewetak. The bomb yielded 15 megatons (13,605,000 metric tons) of destructive force.

The Soviets kept pace with U.S. progress. On November 22, 1955, again at Semipalatinsk, the Soviets' first true hydrogen

bomb detonated. At 1.6 megatons (1,451,200 metric tons and a little over 100 times the force of the Hiroshima bomb), it was the world's first air-dropped hydrogen bomb. The Cold War and the thermonuclear race, referring to nuclear weapons that release atomic energy by joining hydrogen nuclei at high temperatures, had spiraled out of control. Although both the United States and the Soviet Union claimed they did not want to use the H-bombs, the world could only hold its breath and wait.

For More Information

Books

Badash, Lawrence. Scientists and the Development of Nuclear Weapons: From Fission to the Limited Test Ban Treaty, 1939–1963. Amherst, NY: Humanity Books, 1998.

Bethe, Hans A. The Road from Los Alamos. New York: Simon and Schuster, 1991.

Groves, Leslie R. Now It Can Be Told: The Story of the Manhattan Project. New York: Da Capo Press, 1983.

Holloway, David. Stalin and the Bomb: The Soviet Union and Atomic Energy, 1939–1956. New Haven, CT: Yale University Press, 1994.

Isaacs, Jeremy, and Taylor Downing. Cold War: An Illustrated History, 1945–1991. Boston: Little, Brown, 1998.

Kunetka, James W. City of Fire: Los Alamos and the Birth of the Atomic Age, 1943–1945. Englewood Cliffs, NJ: Prentice-Hall, 1978.

Maier, Pauline, Merritt R. Smith, Alexander Keyssar, and Daniel J. Kevles. Inventing America: A History of the United States. New York: W.W. Norton, 2003.

Rhodes, Richard. Dark Sun: The Making of the Hydrogen Bomb. New York: Simon and Schuster, 1995.

Seaborg, Glenn T. Adventures in the Atomic Age. Berkeley, CA: Farrar, Straus, and Giroux, 2001.

Shroyer, Jo Ann. Secret Mesa: Inside Los Alamos National Laboratory. New York: John Wiley and Sons, 1998.

Szasz, Ferenc M. The Day the Sun Rose Twice: The Story of the Trinity Site Nuclear Explosion. Albuquerque: University of New Mexico Press, 1984.

Web Sites

The Atomic Archive.http://www.atomicarchive.com (accessed on July 18, 2003).

Los Alamos National Laboratory.http://www.lanl.gov/worldview/ (accessed on July 18, 2003).

The Manhattan Project Heritage Preservation Association, Inc.http://www.childrenofthemanhattanproject.org (accessed on July 18, 2003).

National Atomic Museum.http://www.atomicmuseum.com (accessed on July 18, 2003).

Russian Research Centre, Kurchatov Institute.http://www.kiae.ru (accessed on July 18, 2003).

"Secrets, Lies, and Atomic Spies." Nova Online.http://www.pbs.org/wgbh/nova/venona (accessed on July 18, 2003).

United States Strategic Command.http://www.stratcom.af.mil (accessed on July 18, 2003).

Words to Know

Atomic bomb: An explosive device that releases nuclear energy (energy that comes from an atom's core). All previous explosive devices were powered by rapid burning or decomposition of a chemical compound; they only released energy from the outermost electrons of an atom. Nuclear explosives are energized by splitting an atom, a process called fission.

Atomic Energy Commission (AEC): A unit established by Congress in July 1946 that managed the nuclear research facilities in Oak Ridge, Tennessee, Hanford, Washington, and Los Alamos, New Mexico.

Cold War: A prolonged conflict for world dominance from 1945 to 1991 between the two superpowers, the democratic, capitalist United States and the communist Soviet Union. The weapons of conflict were commonly words of propaganda and threats.

Communism: A system of government in which the nation's leaders are selected by a single political party that controls all aspects of society. Private ownership of property is eliminated and government directs all economic production. The goods produced and accumulated wealth are, in theory, shared relatively equally by all. All religious practices are banned.

Manhattan Project: A project begun in 1942—during World War II (1939–45)—with the goal of building an atomic weapon before scientists in Germany or Japan did.

Strategic Air Command (SAC): A unit established by the U.S. military with the goal of identifying targets in the Soviet Union and being ready to deliver nuclear weapons to those targets.

People to Know

Lavrenty Beria (1899–1953): Leader of the Soviet secret police and manager of the Soviet bomb project.

Leslie R. Groves (1896–1970): The U.S. Army officer in charge of the Manhattan Project.

Adolf Hitler (1889–1945): Nazi party president, 1921–45; German leader, 1933–45.

Igor Kurchatov (1903–1960): The Soviet Union's premier nuclear physicist, who led the building of the Soviets' atomic bomb in 1948.

J. Robert Oppenheimer (1904–1967): A theoretical physicist who led the building of the United States' atomic bomb during World War II.

Franklin D. Roosevelt (1882–1945): Thirty-second U.S. president, 1933–45.

Harry S. Truman (1884–1972): Thirty-third U.S. president, 1945–53.

"Little Boy" and "Fat Man"

Between 1942 and 1945, Los Alamos scientists produced two types of bombs—or "gadgets," as they were called during development. The bombs were detonated in different ways. One bomb, code-named "Little Boy," used uranium-235 (U-235) and was detonated by a process called fission. Fission involves splitting the atomic nucleus of a heavy element to create two lighter elements. Natural uranium contains two forms of the element mixed together: U-235 and U-238. U-235 is fissionable (split-table); U-238 is not. Therefore, to gather material for bomb making, scientists have to separate U-235 from U-238.

The nuclear research plant in Oak Ridge, Tennessee, took charge of the task to produce the U-235 needed for Little Boy. To detonate Little Boy, a slug of U-235 would be fired like a bullet down a gun barrel into the center of another chunk of U-235. Adding its own fissionable material to the mix, the slug would split the nucleus of the U-235 chunk, causing it to release a tremendous amount of energy in the form of an explosion. Little Boy was 10 feet (3 meters) long and 28 inches (71 centimeters) in diameter; it weighed 9,000 pounds (4,086 kilograms). Scientists were certain that this type of bomb would work and did not actually test Little Boy.

The second type of bomb, code-named Fat Man, used implosion (an extreme inward collapse) to detonate plutonium. A University of California at Berkeley scientist, Glenn T. Seaborg (1912–1999), discovered that a new fissionable element could be made by bombarding uranium-238 with neutrons, one of two kinds of particles found inside the nucleus (central part) of an atom. He named the new element plutonium. The nuclear research plant in Hanford, Washington, was in charge of producing plutonium. Fat Man consisted of high explosives surrounding a plutonium ball. When detonated, the explosives would compress, or squeeze, the plutonium, causing a massive energy release, or explosion. Los Alamos scientists were not sure the plutonium bomb would work, so they conducted the Trinity test of Fat Man on July 16, 1945. The spectacular results confirmed that it indeed worked.

Both types of bombs release energy (explode) as a result of a change in the composition of the atomic nucleus; that is why they are called atomic or nuclear weapons.

A-Bombs and H-Bombs

All the bombs mentioned in this chapter were created by altering the nucleus of the atom of an element, so all of them may be referred to as nuclear bombs or atomic bombs. However, technically, only bombs that are detonated by controlled fission, or the splitting of an atom's nucleus, are true atomic bombs, or A-bombs.

Bombs that are created by the fusion, or joining together, of atomic nuclei of the element hydrogen are called hydrogen bombs, or H-bombs. H-bombs are also called thermonuclear bombs, because of the incredible heat their reaction generates. H-bombs explode with a much greater force than A-bombs.

Although highly destructive, A-bombs are limited in power compared to the boundless destructive force of H-bombs. One kiloton equals the explosive force of (or the energy released by) 1,000 tons (907 metric tons) of TNT, a conventional (nonnu-clear) explosive. One megaton equals the explosive force of 1,000,000 tons (907,000 metric tons) of TNT.

In August 1945, the United States dropped A-bombs on Japan over the cities of Hiroshima and Nagasaki. The Hiroshima bomb, using the code name "Little Boy," had a force of 13,000 tons (11,791 metric tons), or 13 kilotons, of TNT. Its element base was uranium-235. The Nagasaki bomb, using the code name "Fat Man," had a force of 22,000 tons (19,954 metric tons), or 22 kilotons, of TNT. Its element base was plutonium.

Two tests showed the tremendous force of H-bombs. One test, at Enewetak Atoll, on November 1, 1952, had a force of 10,400,000 tons (9,432,800 metric tons), or 10,400 kilotons, or 10.4 megatons, of TNT. Its element base was hydrogen. Another test (given the test code name of Bravo), at Bikini Atoll, on March 1, 1954, had a force of 15,000,000 tons (13,605,000 metric tons), or 15,000 kilotons, or 15 megatons, of TNT. Its element base was hydrogen.

The Strategic Air Command

In 1948, General Curtis E. LeMay (1906–1990), a decorated World War II pilot, assumed command of the U.S. Air Force Strategic Air Command (SAC), which was formed in 1946. Based in Nebraska at Offutt Air Base, the SAC bomber force became the cornerstone for the U.S. national air defensive and offensive strategy. Commanding the nerve center of an eventually worldwide bomber-missile force, LeMay started building his bomber teams into an elite, well-seasoned corps. Deciding that the best defense was indeed an overwhelming offense, LeMay pushed for a buildup of nuclear weapons and for bombers to carry them. As soon as the Soviets demonstrated nuclear capability, LeMay emphasized that SAC needed to have at its disposal enough weapons, and the planes to carry them, to hit thousands of targets in the Soviet Union. By 1952 he had identified up to six thousand Soviet targets. He reasoned that SAC's strength would deter Soviet aggression.

According to Isaacs and Downing in Cold War: An Illustrated History, 1945–

1991, the U.S. military had 298 atomic bombs in 1950, 2,422 nuclear weapons in 1955, and 27,100 by 1962. In 1951, SAC had 668 B-50 and B-29 bombers. By 1959 it had 500 long-range B-52 bombers and more than 2,500 B-47 bombers that could refuel in midair.