The Marshall Islands: U.S. Nuclear Testing of the 1950's

Ryan Castandea
April 7, 2018

Submitted as coursework for PH241, Stanford University, Winter 2018


Fig. 1: The explosion from the Castle Bravo detonation (Source: Wikimedia Commons)

The Marshall Islands, home to the Marshallese people, are a small group of Micronesian islands in the central Pacific Ocean. Throughout the duration of World War II, the islands were occupied by the United States and were eventually made part of the United Nations Trust Territory of the Pacific Islands in 1947. [1] This placed them under the jurisdiction of the United States, who decided to begin using two of the islands, and Enewetak, for nuclear testing during the 1950s. The decision to use these islands was due to the islands climate (warm but not prone to tropical storms), location (remote from continental landmasses), and population (deemed lightly populated). [2] However, based on the aftermath of the nuclear tests, it is clear that the U.S. did not fully consider the consequences of these tests on the islands and their people.

Castle Bravo Detonation

Part of the larger Operation Castle, Castle Bravo was the first and largest of a series of six U.S. nuclear tests conducted in the Bikini atoll. [2] Before the test detonation took place, however, the U.S. government had to ensure that the lightly populated area had been cleared of civilian life. Before the first test on the Marshall Islands took place, there were 167 people living on the Bikini atoll, all of which had to be relocated before the test could be performed. [3] Each of the 167 people were relocated to nearby atolls in the Marshall Islands.

The Castle Bravo device, nicknamed Shrimp, consisted of a solid lithium deuteride fuel contained within a natural uranium tamper and also holding a plutonium sparkplug held within the fuel cylinder. [2] The device was predicted to have a yield of four to eight megatons, but upon detonation the explosion achieved an unexpected and dangerously high yield of 15 megatons, 150% larger than expected and equivalent to 1,000 times the force of the Hiroshima explosion. [2,3] While this test was the first of many in the overall nuclear testing campaign performed in the Marshall Islands, the detonation itself, seen in Fig. 1 to the right, remains the largest in U.S. history. [5]

Impact of Nuclear Radiation

Fig. 2: Topographical map showing the nuclear fallout on the Marshall Islands and surrounding area. [6] (Source: Wikimedia Commons)

Above all, the four atolls that were the most affected by the nuclear tests consisted of Bikini, Enewetak, Utirik and Rongelap. The lasting effects of nuclear fallout on these islands, the pattern of which can be seen in Figure 2 below, caused a plethora of issues for both natives and American servicemen who were inhabiting the islands. Although Bikini was chosen for its location and lack of population, the fact that it was 200 miles closer to the largely inhabited Utirik and Rongelap atolls than the next best option was not taken into consideration. [2] This lack of attention to detail, or blatant misconduct on the part of U.S. officials, led to large amounts of unforeseen nuclear fallout affecting parts of Utirik and Rongelap.

For this reason, hundreds of American servicemen and native Marshallese islanders had to be evacuated from the two atolls following the Castle Bravo nuclear test, but not before ash and other debris rained down on the islands. [3] For the next three months after the evacuation, a total of five more nuclear tests were performed on Bikini and Enewetak, which caused the amounts of radioactive fallout on the nearby atoll of Utirik to increase dramatically. This led Dr. Merril Eisenbud to deem the atoll the most contaminated place in the world during a meeting with the Atomic Energy Commission Advisory Committee on Biology and Medicine. [4] However, based on his statements involving the Utrok people, in which he declared them "more like [civilized people] than mice", as well as his intent to study the effects of human uptake when people live in a contaminated environment, it is clear that the intent of the U.S. did not take into consideration the livelihood of the Marshallese people. [4]

In the following years after the Marshallese people were allowed to once more inhabit the islands, including Utirik, a wide variety of tragic side effects from nuclear radiation could be found all over the atoll. Some of the major examples included a dramatic increase in the number of miscarriages, which increased from three total cases in the islands history before the testing, to over 41 cases by 1954. [4,5] Similarly, the amount of stillbirths increased from one case before the testing to 15 total cases reported after the bombing. [4,5] Along with increases in the number of cancer cases and numerous cases of body deformities, these incidents reveal the dark consequences paid for by the Marshallese people for the sake of U.S. nuclear weapons research during the Cold War.


While the nuclear tests performed on the Marshall Islands may have been aimed at improving the capability of U.S. nuclear weapons and the overall strength of the U.S., the costs to the wellbeing of the Marshallese people was drastically miscalculated. The U.S. used its political strength after World War II to gain control of this territory and abuse its right to use these islands for its own gain. Unlike the many inhabitants of the U.S., the costly effects of this moral lapse during the 1940s-1950s are still felt to this day for the people of the Marshall Islands.

© Ryan Castandea. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] "Marshall Islands," University of Prince Edward Island, 2007.

[2] K. M. Parsons and R. A. Zaballa, Bombing the Marshall Islands: a Cold War Tragedy (Cambridge University Press, 2017).

[3] D. Zak, "A Ground Zero Forgotten," Washington Post, 27 Nov 15.

[4] "Nuclear Testing Program in the Marshall Islands," Committee on Energy and Natural Resources, U.S. Senate, S. Hrg. 109-178. 19 Jul 05.

[5] M. Guttwald, "Marshall Islands Nuclear Testing and Health Effects," Physics 241, Stanford University, Winter 2017.

[6] C. Hansen, The Swords of Armageddon (Chukelea Publications, 1995).