Nuclear Testing Before Nevada (1942-1950)

The Nevada Test Site was the United States’ Cold War continental nuclear proving ground. Nuclear weapons testing began during World War II and came of age during the Cold War. The nuclear tests conducted in Nevada between 1951 and 1992 had their origins in major scientific discoveries of the twentieth century.

Nuclear Weapons Testing and Use during World War II

The world’s first nuclear detonation was the Trinity test, conducted on July 16, 1945 in the Jornada del Muerto area of the central New Mexico desert at the Alamogordo Bombing Range (today the White Sands Missile Range). Trinity was the culmination of the work of the Army Corps of Engineers’ top secret Manhattan Engineer District or Manhattan Project. The creation of the Manhattan Project was made feasible by the work of Italian émigré and Nobel laureate Enrico Fermi and his team at the University of Chicago. In December of 1942, the team produced the first sustained nuclear chain reaction, named Chicago Pile-1. The success of this experiment showed that it was possible to produce a chain reaction capable of sustaining a bomb.

Under the direction of General Leslie Groves, the Manhattan Project had sites around the country including those in Chicago, Illinois, Hanford, Washington, and Oak Ridge, Tennessee. In 1943, the Manhattan Project’s top-secret Los Alamos laboratory, code-named “Site Y,” was established in the isolated mountains of northern New Mexico. There, many of the world’s greatest scientists, including Fermi’s team, labored under the direction of the charismatic J. Robert Oppenheimer to create a functioning atomic weapon with unprecedented explosive power.

In July of 1945, Trinity’s plutonium core implosion device was detonated from a one-hundred foot tower that rose from the desert floor. Trinity’s yield was approximately 21 kilotons—one kiloton is equal to the explosive force of 1000 metric tons of TNT. The explosion created a fire ball 2,000 feet in diameter that lit up the sky for many miles and produced a tremendous mushroom cloud. The extremely high temperatures caused the surface sand of the crater to fuse, transforming it into a green, glassy layer dubbed Trinitite. Many Manhattan Project workers collected pieces of the jade-like material as mementos.

Within one month of the Trinity test, atomic bombs produced by the Manhattan Project were dropped on the Japanese cities of Hiroshima and Nagasaki. The Hiroshima bomb was a uranium gun that had not been tested prior to its use because the scientists were confident that its design would work. Dropped from the United States Army Air Forces’ B-29 bomber, “Enola Gay,” the Hiroshima bomb exploded at about 1900 feet above the ground with a yield of approximately 15 kilotons. Four and one-half square miles around ground zero were completely destroyed. An estimated death toll of 130,000 includes those killed by the blast as well as from acute radiation exposure.

The Nagasaki bomb was the same design that had been proof-tested at Trinity test. It was dropped from the B-29 bomber named “Bockscar.” Its yield was approximately 21 kilotons with an estimated total death toll of 70,000 people. Most of the victims of the bombings were civilians, and many were children. The Japanese surrender and the end of World War II came within days of the Nagasaki attack.

The United States’ atomic bombings of Japan introduced the world to the unprecedented danger and power of nuclear weapons. Oppenheimer believed that the development of nuclear weapons had been inevitable and at the same time represented a fundamental change in the nature of the world. Since the end of the war there has been much debate among military and civilian leaders, politicians, and historians, citizens of Japan and the United States, and the world community about the forces that brought humankind’s most devastating war to an end, the morality of nuclear weapons, and the Cold War nuclear arms race that soon followed.

Post-World War II Nuclear Testing before the Nevada Test Site

After the atomic bombings of Hiroshima and Nagasaki at the end of World War II, the United States’ military and civilian leaders were under enormous pressure to better understand nuclear weapons and their impact on the conduct of warfare. Although many Manhattan Project scientists returned to their peacetime university positions, others remained at Los Alamos to work on the design and development of fission bombs like the Hiroshima and Nagasaki weapons as well as fusion or so-called “Super” thermonuclear bombs, which have unlimited potential yield.

In 1946, ten months after the bombings of Hiroshima and Nagasaki, the U.S. conducted its first peace-time nuclear test series in the Pacific, named Operation Crossroads. The purpose of the test was to determine the atmospheric effects of nuclear weapons on military hardware such as ships, equipment, and material. Such “weapons effects tests” were an important component of the nuclear testing regime throughout the Cold War in the Pacific and at the Nevada Test Site. Operation Crossroads was conducted at Bikini Atoll in the Marshall Islands. Two bombs identical in design to the Trinity and Nagasaki bombs were detonated with the same approximate explosive yield, around 21 kilotons. The first Crossroads test, designated Able, was dropped from an airplane and detonated at an altitude of around 520 feet. Less than month later, the second test, Baker, was detonated approximately 90 feet under the lagoon. It caused significant radioactive contamination for which officials were not prepared. The decontamination efforts themselves were so dangerous to testing personnel that they were halted and the third planned test was cancelled. Crossroads Able and Baker were the first of 106 nuclear tests conducted by the United States in the Pacific.

In mid-1947, President Harry Truman authorized the next nuclear test series with the purpose of testing new implosion weapons designed by Los Alamos laboratory scientists. Operation Sandstone took place at Enewetak Atoll in the Marshall Islands during April and May 1948. It was a large-scale operation involving more than 10,000 people, most of them uniform military. Joint Task Force 7 provided support to the weapons scientists and engineers. In addition to testing the new weapons design, the mission was broad: to construct an atomic weapons proving ground in the Pacific with the needed logistical support; to provide the armed forces the opportunity to participate in nuclear weapons development; to serve as a vehicle for military training; and to contribute national security and preparedness for nuclear war. The series’ three tests were detonated from 200 foot towers: X-Ray had a yield of 37 kilotons, Yoke, 49 kilotons—more than twice the size of Trinity, Hiroshima and Nagasaki—and Zebra, 18 kilotons. Within three years of the Trinity test, the United States had used two atomic weapons in warfare and tested five more.

Although some American scientists predicted that the Soviet Union would be able to produce an atomic bomb within five years of the war’s end, many civilian and military leaders officials expected it would take them at least a decade and perhaps two. However, in 1949, the Soviet Union detonated its first atomic device and the United States’ short-lived monopoly on nuclear weapons ended. The United States next test series was Operation Ranger, conducted in January and February 1951 at the newly established Nevada Test Site.

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