Nuclear Testing in the Marshall Islands and the Fallout on People There

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Between 1946 and 1958, after their populations were resettled, the United States conducted 67 nuclear tests in and around Bikini and Enewetak Atolls. The people from Ailinginae and Rongelap Atolls were also evacuated because of nuclear fallout, and all four atolls remain largely uninhabited. [Sources: John Eliot, National Geographic, June 1992 and National Geographic, June 1986]

The tests began almost immediately after the end of World War II. In July 1946, the United States began atmospheric and underwater test of weapons designs in the Marshall Islands. A total of 23 bombs were detonated at Bikini Atoll and 43 were set off at Enewetak Atoll before the testing program was stopped in 1958. Kwajalein Atoll was later used as a missile testing area.

Bikini was selected as a test site because it was isolated from sea and air routes and the winds blew in predictable patterns, and thus blew the radiation clouds in predictable ways. Over 3,000 animals were used in a test at Bikini, including a pig known as Number 311 that leapt from a sinking ship and was retrieved from the water and lived to a ripe old age at the National Zoo in Washington D.C.

The first hydrogen bombs (H-bombs) were tested in the Marshall island.The largest United States bomb ever exploded was an H-bomb detonated in Bikini on March 1, 1954 (See Operation Bravo Below). The largest thermonuclear device ever exploded (57 megatons) was detonated by the Soviets in the Novaya Zemlya area on October 30, 1961.

The nuclear tests ended in 1958 with ths signing of international test-ban treaty. Radiation contamination from the nuclear testing program resulted in the displacement of the indigenous people of Bikini and Enewetak.

Marshall Islands, the Bikini and Nuclear Bombs

The Marshall Islands consist of two chains of 29 coral atolls, and are located north of the equator, between Hawaii and Australia. On each atoll there are a number of islands. Due to their remote location, sparse population, and other nearby U.S. military bases, the U.S. decided to test powerful nuclear weapons there. In 1947, the Marshall Islands became part of the Trust Territory of the Pacific Islands, created by the United Nations and then administered by the U.S. In 1946, the islands had a population of 52,000. [Source: Atomic Heritage Foundation, National Museum of Nuclear Science & History]

During the post-World War II period the U.S. expanded their nuclear research and development programs. The U.S. government established the Atomic Energy Commission (AEC) to monitor the peacetime development of atomic science and technology. Fear of the Soviet Union increasing their atomic weapons, and the belief that building up nuclear arms could help establish U.S. power, contributed to this rapid expansion.

The first testing series in the Marshall Islands occurred under Operation Crossroads (See Below). These tests were the first time that the U.S. tested nuclear weapons since the Trinity Test in 1945. These were also the first U.S. nuclear detonations since the “Little Boy” and “Fat Man” bombs dropped over Japan.

The bikini bathing suit was introduced in July, 1946, the same month the first atom bombs were detonated at Bikini. The swimwear was first named “atome” by its French designer Louis Réard , who was also an automobile engineer.

The Soviet Union became the world’s second nuclear power after the United States when it detonated its first atomic bomb, "Joe 1," in Kazakhstan in August 1949. The bomb was a copy of the Fat Man bomb. United States "sniffer" planes picked up fallout from the test. The design for the bomb was stolen from the U.S. by the German-born spy Klaus Fuchs.

The concept for hydrogen fusion bombs — a devise many times more powerful than atom bombs — was first presented by U.S. physicist Edward Teller in 1942. In January 1950, U.S. President Harry Truman authorized Teller to tell the United States army about hydrogen bomb a couple of months after Joe 1. Teller's initial design didn't work. A Polish mathematician at Los Alamos, Stanislaw Ulam, advised him to make an effective two-stage design.

Timeline of Major Nuclear Tests Conducted at the Marshall Islands:

July 1, 1946 — Testing begins at the Marshall Islands, with Shot Able. [Source: Atomic Heritage Foundation, National Museum of Nuclear Science & History]

July 25, 1946 — Shot Baker is conducted, under Operation Crossroads.

April 30, 1948 — Shot Yoke, under Operation Sandstone, is conducted. This was the first fission weapon to use a levitated core design.

April 20, 1951 — Shot Easy nuclear test is conducted at Enewetak Atoll, under Operation Greenhouse. The Easy test was meant to test a new, lighter implosion bomb.

January 1950 — President Truman made the decision to increase U.S. research into thermonuclear weapons, which would lead to further U.S. nuclear testing.

May 1951 — Operation Greenhouse testing occurred at Enewetak Atoll. This series of nuclear tests were done to test design principles that would later become pivotal in the development of the hydrogen bomb. The tests aimed to reduce the overall size of nuclear weapons, including the necessary amount of fissile material, while increasing their destructive power.

November 1, 1952 — The Mike Shot is conducted at Enewetak, under Operation Ivy. This was the first U.S. thermonuclear test. On November 16, the U.S. conducted the King Shot.

June 28 1958 — The Oak test is conducted, at Enewetak Atoll, under the Operation Hardtack I series. This was the 6th largest U.S. nuclear test. Hardtack I included 35 total tests. Hardtack I was the last testing series conducted on the Marshall Islands.

Operation Crossroads and the Bikini

On July 1 and July 25, 1946, less than two years after the bombs were dropped on Hiroshima and Nagasaki, two atom bombs were detonated at Bikini atoll before a huge audience of American politicians, foreign dignitaries and scientist as part of test dubbed Operation Crossroads.

The purpose of Operation Crossroads was to investigate the effect of nuclear weapons on naval warships and measure the effectiveness of nuclear bombs against a fleet of enemy ships. Anchored in Bikini’s lagoon were nearly 93 unmanned decommissioned and captured warships, including the Japanese battleship “Nagato, the German cruiser “Prinze Eugen, the U.S. battleships “Nevada” and “Arkansas” and the U.S. aircraft carrier “Saratoga.

Testing in the islands began at Bikini Atoll with the Shot Able test, on July 1, 1946. The bomb was dropped from a B-29 and exploded 500 feet above the lagoon, The one on July 25, codenamed Shot Baker, was detonated under water. Each bomb created an explosion equal to 20,000 tons of TNT

The events were recorded by 42,000 men, 142 other ships, 10,000 instruments 200 movie cameras and 18 tons of film (half the world's supply at that time). Much of the real footage of nuclear explosions that we see today was taken as part of Operation Crossroads. Radio stations in the U.S. broadcast the explosions live.

Damage Caused By Operation Crossroads

Twelve large vessels and ten smaller ones were sunk by the Operation Crossroads explosions, including the “Saratoga” which severally damaged and blown 800 meters away by the first bomb, and sunk by the second bomb, which was detonated 800 meters away from the ship and produced a 13-meter (43-foot) wave.

The “Arkansas” and “Nagato” and the submarines “Pilotfish” and “Apogon” also went down after being deluged by water and sediment that was hurled more than a mile into the sky. These ships are visited by scuba divers today.

The ships that remained afloat were badly contaminated with high-levels of radiation that was absorbed by sailors who boarded the ships to wash scrub and paint the "hot" metal.: More than 1,000 veterans at the test later filed disability claims for radiation-induced cancer.

After Shot Able, the Bulletin of the Atomic Scientists confirmed the awesome power of nuclear weapons. They determined that soldiers on ships up to a mile away from this explosion would be instantly be killed. Operation Crossroads ended on August 10, 1946, due to concerns over radiation, especially to the soldiers involved.

A month later, the Marshallese filed a complaint with the UN, but this did not prevent U.S. nuclear testing. In 1948, the U.S. government forced residents of Enewetak Atoll to evacuate due to expanded nuclear testing with Operation Sandstone.

Operation Bravo

On March 1, 1954, a 15-megaton hydrogen bomb was detonated over Bikini atoll. Dubbed "Operation Bravo," the explosion was 1,000 times more powerful than one at Hiroshima and the power of the bomb was greater than all the explosives used in World War II. It was the largest bomb ever exploded at the time. A freight train carrying the equivalent amount of TNT would span the North American continent.

The Bravo Test was officially called Castle Bravo. It was part of Operation Castle, a series of thermonuclear tests. Bravo was the first test of a deliverable hydrogen bomb. It used a device called “Shrimp” which used lithium deuteride as its fuel. [Source: Atomic Heritage Foundation, National Museum of Nuclear Science & History]

Despite potential risks, Major General Percy Clarkson and scientific director Dr. Alvin C. Graves ordered the test to continue as planned. Due to Castle Bravo radioactive debris was released into the atmosphere, and to surrounding atolls. The test was more powerful than scientists predicted. Ocean currents, weather conditions, and wind patterns contributed to this spread of fallout and debris.

A geological study of a 9.8 megaton hydrogen bomb detonated at Enewetak Atoll in 1958 showed that the explosion dug out a mile-wide, 200-feet-deep crater in the lagoon and fractured rock 1,400 feet beneath the carter.

Fallout from Operation Bravo

The fallout was composed of pulverized coral, water, and radioactive particles, and it fell into the atmosphere appearing as ashy snowflakes. This affected nearby atolls and U.S. servicemen. Traces of radioactive material were later found in parts of Japan, India, Australia, Europe, and the United States. This was the worst radiological disaster in U.S. history and caused worldwide backlash against atmospheric nuclear testing. [Source: Atomic Heritage Foundation, National Museum of Nuclear Science & History]

Fallout and pulverized coral from the hydrogen bomb explosion covered a 130,500-square-kilometer (50,000-square-mile) area including the inhabited islands of Rongelap, Utrik and Rongerick. A man died of radiation expose on Fukuryu Maru, a Japanese fishing vessel that was in the path of the radiation cloud. There were 232 crew members aboard the ship. The man who died died six months after the blast. The survivors suffered serious health problems. As of the early 2000s, 12 had died. Some are believed to have died from diseases related to radiation exposure. The Fukuryu Maru was 160 kilometers east of the test site, fishing for tuna, at the time of the explosion,

Twelve hours before the bomb was to go off. U.S. officials realized that high altitude winds would carry radioactive fallout over Rongelap. Americans in the affected area were evacuated immediately but Marshallese were not moved until three days after the explosion.

After the nuclear tests the fish around the test areas were so contaminated with radiation that the navymen who caught then immediately threw them back into the sea. But today th ocean ecosystem appears to have returned to normal as evidenced by the large number of healthy sharks and predators (the top of the food chain) that patrol the waters.

Fish in Bikini atoll are largely free of radiation but the soil, ground water and plants are contaminated with by lethal cesium 137 radiation, most of it produced by the Bravo explosion. Eating a single coconut with cesium 137 will not cause nay problem but eating many such coconuts over period of time may like possibly cause serious health problems. Cesium 137 has a half life of 30 years, and it is estimated that it will take another 70 or 80 years for cesium to be reduce acceptable levels. Experiments have shown that potassium compounds such as those found in fertilizer can be used to block the intake of cesium by food crops.

Bikini Islanders and Nuclear Testing

Bikini, the main island of Bikini atoll, was a lovely island with beautiful beaches. According to legend, it was the favorite island of Loa, the god who created the Marshall Islands. The Bikini islanders were a religious, trusting people.

Bikini was chosen as a testing site by the Truman administration. In 1946, Navy Commodore Ben Wyatt met with the 167 people living on Bikini Atoll and told them their islands were needed for "a greater good" and told they would be allowed to return to their homes after the testing was over. He said that the Bikini islanders were a chosen people and that perfecting atomic weapons could prevent future wars.

Impressed by American firepower they saw during the war and persuaded by arguments that the tests were for the benefit of mankind, the Bikini islanders felt they had no had no choice but go along with the American proposal. The chief, Juda, announced "If the United States government and scientists of the world want to use our island and atoll from furthering development, which with God’s bless will result in kindness and benefit to all mankind, my people will be pleased to go elsewhere."

In truth the residents had no choice in this matter. Immediately following Wyatt’s meeting speech, the U.S military began preparations to relocate the residents to Rongerik Atoll, an uninhabited island with limited resources 125 miles away. [Source: Atomic Heritage Foundation, National Museum of Nuclear Science & History]

Relocation of the Bikini Islanders

In the early 1946, the 167 Bikini islanders from 11 families were relocated to another island under the promise they could return after the tests were finished. They took thatch for new roofs and dismantled their church and community hall and took that with them. Thus began an odyssey in which the Bikini islanders were gave up of their way of life and found themselves transplanted to islands where they were not happy.

The first of 23 tests which took place at Bikini began a few months after the islanders left. The Bikinians were first taken to Rongerik Atoll, where they got sick from eating poison fish and nearly starved from the lack of inadequate food supplies. In 1948, the Bikinians were moved to Kwajalein Atoll and later to Kili island a mere dot of land only 230 acres in size. Kili is a solitary island with a lot of surf crashing on its shores. In the mid 1980s about the Bikini Islanders remained in Kili and half were scattered around the other Marshall islands.

In the 1970s, the Bikinians were told it was safe to return home and many did, only to find two of the islands had disappeared and others were treeless and covered with debris. Even so they decided to stay and make a living the best they could until 1978 when they were told that food grown in the radiation-contaminated soil was unsafe and they were relocated again.

Bikini Islanders on Kili received supplies from supply ships and planes. But when the supply ships didn’t appear on time many islanders suffered from hunger or were eaten by sharks when motors on the boats conked out and they tried swimming to shore.

As of the 1990s many Bikini Islanders are bored out their skulls and overcome with a sense of despair over their fate. They spent a lot of time sitting around doing nothing Those on other islands were the objects of ridicule by other islanders. Many of the old customs died as old men have died. Younger people were addicted o welfare. They had little interest in returning to Bikinis and have grown lazy with United States supplied food and housing. Alcohol was banned and there is little to eat other chicken and rice. The birthrate was high. Bikini Islanders are prone to diabetes. Food and drink supplied by the United States government such as peaches in syrup, Spam and Fanta grape soda haven’t helped.

There are good documentaries about Bikini: “Radio Bikini” (produced by Public Broadcasting in 1988) and “Bikini: the Forbidden Paradise” (produced by ABC in 1993).

Plight of the Ronelapese

The residents of Rongelap Atoll, 160 kilometers (100 miles) downwind from the 15 megaton 1954 Operation Bravo hydrogen bomb blast, were blanketed by fallout ash six hours after the explosion. The 253 residents of the atoll were not evacuated to Kwajalein until three days after the detonation. Some inhabitants suffered from radiation sickness, lost their hair and had severe burns hours after they were blanketed by "Bikini snow," which some curious islanders played with and even tasted.

The Rongelapese returned to their atoll three years after the explosion in 1958 after the islands were declared safe. The Rongelapese then suffered form abnormally high rates of mental retardation, leukemia, stillbirths and miscarriages. Almost three quarters of the people under the age of ten at the time of the blast had surgery to remove thyroid tumors. In 1985, the Rongelapese were evacuated again.

The U.S. military had claimed that the Rongelapese were exposed to radiation as a result of last minute change in wind direction in 1954. Testimony before Congressional committee in 1994, revealed that military officials at the testing site had been warned at least a day before of the wind direction changes by U.S. meteorologists.

Many Rongelapese islanders died and had health problems linked to their exposure to radiation. Some islanders feel they were deliberately used as guinea pigs without their knowledge. In 1985, the Greenpeace ship “Rainbow Warrior” moved the Rongelapese to a new home on Mejato Island in Kwajalein Atoll.

The residents of Ulrik Atoll were also exposed to radioactive fallout and they too have experienced health problems linked to their radiation exposure. The Marshall Islands has the highest incident of radiation-induced illnesses.

Compensation and Decontaminating Bikini Atoll

In 1983, the United States gave $183.7 million to the Marshalls for damages from the tests. A nuclear claims tribunal established in 1988 by the Marshalls subsequently recognized more than $2 billion in compensation claims; islanders sued in U.S. court in 2006 to force the United States to pay the unfunded awards but were unsuccessful. [Source: The Columbia Encyclopedia, 6th ed, Columbia University Press]

Fifty years after testing began, Bikini Island began to attract a few tourists. Scientific surveys have declared the island habitable again, although there is still a danger in eating too many of the local coconuts. Despite the scientific assurances, the US government has yet to issue a statement saying that the island is safe to inhabit. [Source: “Worldmark Encyclopedia of Nations”, 2007,]

In 1969, the U.S. began a long term project to decontaminate Bikini Atoll. At that time there was talk of be removing the top 12 inches of soil to reduce the cesium levels. But the plan would cost $100 million and would remove much land on a 560 acre island and destroy 25,000 trees. Disposal of the cesium-laced material would present other problems.

Contaminated items and soil at Enewetok were gathered together and placed under an 18-inch-thick concrete dome nicknamed Cactus Crater. The island now is considered to have radiation levels low enough for people to live there. The clean up there took three years and cost $120 million.

As of the 1990s the U.S. Department of Energy was still trying to figure out the best way to clean up the islands. The best solution they have been able to come up with is removing all the soil on the islands and replacing it with imported soil, a project which is expected to cost $200 million or more. As U.S. construction crews clean up the mess, the Marshallese government was studying a proposal to turn the atoll into a nuclear waste dump site.

Image Sources:

Text Sources: CIA World Factbook, 2023; “Encyclopedia of World Cultures, Volume 2: Oceania,” edited by Terence E. Hays, 1991, Wikipedia,, New York Times, Washington Post, Los Angeles Times, Times of London, Lonely Planet Guides, Library of Congress, The Guardian, National Geographic, Smithsonian magazine, The New Yorker, Reuters, Associated Press, AFP, BBC, CNN, and various books, websites and other publications.

Last updated August 2023

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