30+ Years of Freedom of Information Action

Bikini A-Bomb Tests July 1946

Published: Jul 22, 2016
Briefing Book #555

Edited by William Burr with Stav Geffner

For more information contact:
William Burr at 202/994-7000 ornsarchiv@gwu.edu.

Underwater Atomic Blast Contaminated Test Ships Making Them “Radioactive Stoves”

Declassified Documents, Films and Photographs Depict Tests "Able" and “Baker” and Removal of Bikinians

Bikini A-Bomb Tests July 1946

Washington, D.C., July 22, 2016 - U.S. atomic tests in Bikini Atoll in July 1946 staged by a joint Army-Navy task force were the first atomic explosions since the bombings of Japan a year earlier. Documents posted today by the National Security Archive about “Operation Crossroads” shed light on these events as do galleries of declassified videos and photographs. Of two tests staged to determine the effects of the new weapons on warships, the “Baker” test was the most dangerous by contaminating nearby test ships with radioactive mist. According to the Joint Chiefs of Staff’s Evaluation Board, because of the radioactive water spewed from the lagoon, the “contaminated ships became radioactive stoves, and would have burned all living things aboard with invisible and painless but deadly radiation.”

The Baker test caused a radiological crisis because task force personnel were assigned to do salvage work on contaminated test ships. Stafford Warren, the task force’s radiation safety adviser, warned task force chief Admiral William Blandy of the danger of these activities: the “ships were “extensively contaminated with dangerous amounts of radioactivity.” It was not possible to achieve “quick decontamination without exposing personnel seriously to radiation.” These warnings eventually led Blandy to halt decontamination activities although only after many military and civilian personnel had been exposed to radioactive substances.

Observers from the United Nations Atomic Energy Commission, including two from the Soviet Union, viewed the Crossroads tests from a safe distance. Recently declassified documents shed light on the emerging Cold War atmosphere; one of the observers, Simon Peter Alexandrov, who was in charge of uranium for the Soviet nuclear project, told a U.S. scientist that the purpose of the Bikini test was “to frighten the Soviets,” but they were “not afraid,” and that the Soviet Union had “wonderful planes” which could easily bomb U.S. cities.

The U.S. Navy’s early March 1946 removal of 167 Pacific islanders from Bikini, their ancestral home, so that the Navy and the Army could prepare for the tests, is also documented with film footage. The Bikinians received the impression that the relocation would be temporary, but subsequent nuclear testing in the atoll rendered the islands virtually uninhabitable.

Operation Crossroads 70 Years Later

Seventy years ago this month a joint U.S Army-Navy task force staged two atomic weapons tests at Bikini Atoll in the Marshall Islands, the first atomic explosions since the bombings of Japan in August 1945. The first test, Able, took place on 1 July 1946. The second test, Baker, on 25 July 1946, was the most dangerous, contaminating nearby ships with radioactive fallout and producing iconic images of nuclear explosions later used in Stanley Kubrick’s Dr. Strangelove. Documents posted today by the National Security Archive, shed light on Operation Crossroads, as does a gallery of videos and photographs.

The Navy, worried about its survival in an atomic war, sought the Bikini tests in order to measure the effects of atomic explosions on warships and other military targets. Named Operation Crossroads by the task force’s director, Rear Admiral William Blandy, the tests involved a fleet of 96 target ships, including captured Japanese and German warships. Both tests gave the U.S. military what it sought: more immediate knowledge of the deadly effects of nuclear weapons.

The U.S. Navy’s early March 1946 removal of 167 Pacific islanders from Bikini, their ancestral home, so that the Navy and the Army could prepare for the tests, is also documented with film footage. The Bikinians received the impression that the relocation would be temporary, but subsequent nuclear testing in the atoll rendered the islands virtually uninhabitable.

Observers from the United Nations Atomic Energy Commission, including two from the Soviet Union, viewed the Crossroads tests from a safe distance. Recently declassified documents shed light on the emerging Cold War atmosphere; one of the observers, Simon Peter Alexandrov, who was in charge of uranium for the Soviet nuclear project, told a U.S. scientist, Paul S. Galtsoff, that while the purpose of the Bikini test was “to frighten the Soviets,” they were “not afraid,” and that the Soviet Union had “wonderful planes” which could easily bomb U.S. cities.

Today’s posting contains a number of primary source documents on the planning of Operation Crossroads and assessments of the two tests, including:

  • An estimate from Los Alamos Laboratory of the planned underwater atomic test: “There will probably be enough plutonium near the surface to poison the combined armed forces of the United States at their highest wartime strength.”
  • A report by an Army officer on the Able test, which exploded in mid-air above an array of warships, conveyed Army-Navy tensions: Noting that Admiral Blandy had painted a “very optimistic picture from the Navy point of view” of the damage done to the ships, “when we examined the target fleet through our field glasses [we saw] that even on the major capital ship, superstructures had been severely damaged.” “The target fleet had indeed suffered a staggering blow.”
  • The Joint Chiefs of Staff (JCS) Evaluation Board noted in a message sent after the Baker test that because of the radioactive water the Baker test spewed upon the ships, the “contaminated ships became radioactive stoves, and would have burned all living things aboard with invisible and painless but deadly radiation.”
  • According to a Navy observer’s report, the two tests were “spectacular and awe-inspiring,” but the “radiological contamination of the target vessels which followed the underwater burst was the most startling and threatening aspect.”
  • The contamination of the target ships caused by the Baker test led Stafford Warren, the task force’s radiation safety adviser, to warn Admiral Blandy of the danger of continuing decontamination work to salvage the ships: the ships were “in the main extensively contaminated with dangerous amounts of radioactivity.” It was not possible to achieve “quick decontamination without exposing personnel seriously to radiation.” These warnings eventually led Blandy to halt the cleanup effort.
  • The Joint Chiefs of Staff Evaluation Board’s final report on the Crossroads tests called for U.S. superiority in atomic weaponry and Congressional action to give the U.S. Presidents license to wage preventive war against adversaries which were acquiring nuclear weapons. The Crossroads report was suppressed for years until it was declassified in 1975.

Planning the First Post-War Atomic Tests

Beginning in late August 1945, shortly after Japan’s surrender, Army Air Force leaders proposed to the U.S. Navy that captured Japanese warships be sunk with atomic bombs. Convinced that air power had decisively defeated Germany and Japan, they believed that naval forces were becoming outmoded. Navy leaders saw a potential threat to their survival but nevertheless believed that warship technology could adjust to a new environment: “ships were not excessively vulnerable to atomic attack” and aircraft carriers were “just as useful as valuable as Air Force bombers for the delivery of atomic weapons.” In October 1945, the Navy responded positively to the Air Force proposals and Chief of Naval Operations Admiral Ernest J. King suggested to the Joint Chiefs of Staff aerial and underwater atomic tests against captured Axis ships and surplus U.S. warships.[1]

By January 1945 President Harry S. Truman had approved a Joint Chiefs of Staff plan for one aerial and two underwater tests as well as a Joint Task Force to conduct them. To stage the tests the Navy sought a remote site under U.S. control where it could assemble ships and atomic explosions that would not endanger large populations. By December 1945, Navy planners had decided that the most suitable location was Bikini Atoll, part of the Marshall Islands group, which had been captured from the Japanese in early 1944. The atoll’s people were descendants of communities that had lived there for thousands of years, subsisting on coconuts and seafood. In order for Admiral Blandy’s task force to prepare for Crossroads, the Navy began to take over the atoll. In February 1946, Commodore Ben Wyatt, the Marshall Island’s military governor, informed the Bikinians that they must leave so that the U.S. government could conduct military tests “for the good of mankind.” On 7 March1946 the Navy transported the Bikinians to Rongerik Island where, as it turned out, food and water were in short supply.

Over 42,000 U.S. military and civilian personnel, of whom 38,000 were naval personnel, participated in preparations and activities relating to Crossroads. The task force included eight task groups with such responsibilities as communications and electronics, photography, instrumentation, safety/security, and the inspection of target ships, among others. Fifteen universities were involved and so were many corporations and nongovernmental organizations. Part of the work included deploying military equipment to be exposed to the tests (the Army alone had 3,000 personnel assigned to measure damage to army equipment exposed to the explosion). The fleet of target ships included 94 aircraft carriers, battleships, cruisers, destroyers, submarines, and landing craft, among other ships. Some of the vessels had been declared excess inventory after the Navy had scaled down its forces, and others had been damaged during World War II. Three German and Japanese warships captured during the war were among the ships to be targeted. The large number of personnel involved and the costs of maintaining the ships made Crossroads the most expensive nuclear test series in history, about $2.2 billion in 2016 dollars.[2]

Stressing the “defensive” aspects of Crossroads, the Navy organized a massive publicity campaign that influenced media and radio coverage for months. Public criticism then emerged, domestically and internationally, leading to an intensified public relations effort.

Although the Cold War had not yet begun, U.S.-Soviet relations were uneasy, and U.S. critics expressed concern that a “grandiose display of atomic power” (Sen. Scott Lucas, D-Ill.) would increase international tensions. Moreover, the first test, scheduled for 15 May, would send the wrong signal when Washington was involved in United Nations discussions over international control of atomic energy. Some opponents worried about a waste of resources while plans to expose test animals to radioactivity generated protest letters from members of the Society for the Prevention of Cruelty to Animals. Skeptical scientists argued that the tests would produce no new information and in a letter to President Truman, former Manhattan Project director J. Robert Oppenheimer argued that mathematical calculations and model tests would produce better data. In light of the conflict with the U.N. discussions, President Truman ordered the first test to be postponed until 1 July.

Some senior advisers to the U.S. government believed that the atomic tests were diplomatically useful. In a discussion at the Council on Foreign Relations, Harvard University president James B. Conant, who had served as wartime chairman of the National Defense Research Committee during World War II, argued that the “Russians are more likely … to come to an effective agreement for the control of atomic energy if we keep our strength and continue to produce atomic bombs.” Truman administration officials may well have seen the tests as bolstering the U.S. position in negotiations with Moscow; certainly, senior U.S. military officials at the time believed the bomb was vital to maintaining “a position of paramount military power” and possibly a “crucial factor in our effort to achieve first a stabilized condition and eventually a lasting peace.”[3]

To support the message that the tests were for defensive purpose, the Truman administration invited journalists and international observers to view the atomic detonations from safe distances. The latter consisted of two representatives each from countries belonging to the United Nations Atomic Energy Commission (UNAEC)--Australia, Brazil, Canada, China, Egypt, France, Mexico, the Netherlands, Poland, the United Kingdom, and the Soviet Union--which were then discussing the plans for international control of atomic weapons. The U.N. observers and U.S. government officials would sail on the U.S.S. Panamint, in a voyage which lasted several months. With at least one U.S. intelligence officer on the ship, the observers, especially the two from the Soviet Union, were likely targets of U.S. efforts to collect intelligence information on the Soviet atomic program.

The Able and Baker Tests

The first test, Able on 1 July 1946, involved an air burst directly above the target ships. “Dave’s Dream,” a B-29 Superfortress which carried out the initial test run for Able, dropped a “Fat Man” plutonium bomb (the type dropped on Nagasaki), with an explosive yield of 23 kilotons. In an error which has never been fully explained, the bomb missed its target by several thousand feet, inadvertently destroying one of the ships carrying measuring instruments. The error created a storm of criticism. The blast did not destroy large numbers of target ships, but five sank and some 40 others were damaged, many of them rendered useless, a “staggering blow” according to an Army officer with the Manhattan Project. Yet media representatives, on ships 20 miles from the test and too far away to experience Able’s shock waves, expressed disappointment, treating it as a virtual dud.[4] By contrast, in a top secret report written a few weeks after Able, the JCS Evaluation Board wrote that all personnel on ships within a mile of the detonation would have been killed by gamma rays and neutrons produced by the “initial flash.”

The Crossroads tests were the subject of intense media coverage and dominated the front pages with scores of journalists from the U.S. and overseas covering the Able test (somewhat fewer attended the second test). Members of Congress also attended, as did a cabinet member (Secretary of the Navy James Forrestal) and the representatives from the UNAEC. Even though basic information about atomic weapons (e.g., production, design, yield, and effects) was highly classified, as was information about the results of the tests, according to the Manhattan Project’s report on Crossroads, "it has been truly said that the operation was ‘the most observed, most photographed, most talked-of scientific test ever conducted.’ Paradoxically, it may also be said that it was the most publicly advertised secret test ever conducted."[5]

The second test, Baker, on 25 July 1946, an underwater nuclear detonation, was, according to the Task Force history, “a giant and unprecedented spectacle.” It produced a huge column of a million tons of water over a mile high, and 80 to 100 waves spread radioactive fallout on nearby ships, partly through rain and partly through a “moving column of radioactive mist.”[6] The column of water lifted the battleship Arkansas before plunging it into the lagoon. Nine ships eventually sank, including another battleship and an aircraft carrier. But the most serious damage was unseen. According to the initial report by the JCS Evaluation Board, the radioactive hazard produced by the spread of water was so dangerous that “after 4 days it was still unsafe for inspection parties operating within a well-established safety margin, to spend any useful length of time at the center of the target area or to board ships anchored there.” Of the test animals in the target ships, all of the pigs died within a month. Even though military experts had predicted the spread of radioactivity months before, its intensity came as a surprise.[7]

Post-Baker Radiation Crisis

Within a few days of Baker, the Joint Task Force initiated decontamination efforts to salvage the target ships for future use, including the scheduled third test, Charlie. However, Stafford Warren, the task force’s radiological safety adviser, was concerned about excessive contamination and insufficient monitors to keep track of radiation hazards. Warren saw a variety of risks: contamination of work clothing and gear bringing the radioactive hazard back to the support ships, radioactivity in the seawater, and the concentration of radioactivity in marine life, such as algae. Especially worrisome to Warren was beta radiation (which can travel short distances in the air and penetrate human skin), and what he saw as growing evidence that the ships were heavily contaminated by alpha-emitters produced by plutonium particles, “the most poisonous chemical known.” Under these circumstances Warren repeatedly pressed a reluctant Admiral Blandy to halt the decontamination efforts and remove personnel from the lagoon. Blandy and the Navy officers were slow to this advice because they did not grasp that the radiation threat could be dangerous even if ship decks were spotless. Nevertheless, Warren persisted and by 10 August a reluctant Blandy ordered a halt to the contamination effort; soon, thousands of task force personnel were leaving Bikini. While the Able test had physically damaged or destroyed ships, the Baker test showed that radioactivity could disable a fleet.

Warren was later criticized for being excessively cautious and pessimistic about the radiation hazard from the decontamination effort, but at the time task force radiation monitors wondered about the long-term impact of the exposure. A few weeks after Baker, one of the radiation monitors, William Myers, wrote to Warren that he did not believe that anyone sustained any “permanent” injury from Baker. Yet he was concerned about the long-run impact because “many of us probably received much more penetrating, ionizing radiation than instruments of very low beta-sensitivity were able to record.” Myers was raising a question that concerned senior officials, such as General Leslie Groves, who worried that Crossroads veterans would make legal claims against the government for injuries caused by radiation exposure. No meaningful attempts were made to identify those who experienced damaging internal exposure, but during the years that followed, some veterans became cancer victims and sought compensation from the federal government. Few got anywhere with their claims until 1988 when Congress passed legislation eliminating the need to prove their exposure.[8]

While Blandy was making decisions about the radiation crisis caused by the Baker test, he was also planning for the deep underwater test, Charlie, scheduled for April 1947. At the same time, however, senior officials in the Manhattan Project and the Pentagon were calling for cancellation of the third test on the grounds that it had had no military value; even more important, making another bomb available for the test would detract from the efforts of Los Alamos Laboratory to design and produce a lighter and smaller atomic weapon. The Joint Chiefs of Staff accepted the case against Charlie and agreed to indefinitely postpone it.

Over a year after Crossroads, the Joint Chiefs of Staff Evaluation Board, chaired by MIT President Karl Compton, completed its top secret report on the tests. Highly controversial, the report was not declassified until 1975, even though some of the board members urged public release of an excised version. By the time the report was finished, the Cold War was ongoing and the recommendations for maintaining nuclear superiority were consistent with the new foreign policy climate. Yet the discussions of the effects of nuclear war were unsettling: according to the report, the use of atomic weapons and other weapons of mass destruction, such as biological warfare, would make it “quite possible to depopulate vast areas of the earth's surface, leaving only vestigial remnants of man's material works.” But proposals that Congress give the President authority to wage preventive war against other nations that were developing nuclear weapons capabilities were especially contentious. In the end secrecy prevailed: the State Department and the Defense Department did not want detailed discussions of atomic warfare and weapons effects to be in the public domain, and unveiling preventive war arguments was diplomatically impossible.

The people of Bikini Atoll had the impression that they would be able to return sometime after the tests, but they never could, and the Bikinians’ malnutrition as a result of their Rongerik resettlement was bad press for the Navy. After a temporary move to Kwajalein, they settled in Kili Island, 400 miles south of Bikini. That settlement was also unsatisfactory but Bikini became uninhabitable because of massive contamination caused by the 1954 Castle Bravo test. A U.S. government effort to relocate the Bikinians back to their home atoll in the late 1960s proved disastrous because U.S. officials had seriously underestimated how much contaminated coconut the Bikinians would be consuming. In 1978, Washington relocated the Bikinians, mostly toKili Island where it has been difficult to sustain traditional ways of life. Several lawsuits during the 1980s led to a $75 million settlement and the creation of a $110 million trust for environmental cleanup and resettlement of the Bikinians. Today, few people live on the atoll, which has become a UNESCO World Heritage site, but climate change threatens its existence.



[1] . This text, and the selection of documents, relies heavily upon the most comprehensive and wide-ranging account of Crossroads, Jonathan M. Weisgall’s Operation Crossroads (Annapolis, Naval Institute Press 1994). Also helpful was the chapter on Crossroads in James P. Delgano’s Nuclear Dawn: the Atomic Bomb from the Manhattan Project to the Cold War (Botley, Oxford, Osprey Publishing, 2009), 138-162.

[2]. Stephen Schwartz et al., Atomic Audit: The Costs and Consequences of the U.S. Nuclear Weapons Program, 1940-1998 (Washington, D.C.: Brookings Institution, 1998), 99-101; e-mail from Stephen Schwartz, 12 July 2016.

[3] . James B. Hershberg, James B. Conant: Harvard to Hiroshima and the Making of the Nuclear Age (Stanford, Stanford University Press, 1995), 267. Quotations by Assistant Chief of Naval Operations Admiral Robert Lee Dennison and Army Air Force commander Carl Spaatz, Melvyn P. Leffler A Preponderance of Power: National Security, the Truman Administration, and the Cold War (Stanford: Stanford University Press, 1992), 116.

[4] . The Soviet observers, Alexandrov and Mescherayako, sent reports to Moscow that were incorporated into a memorandum for Molotov on the Bikini tests. The comments on the first test indicated “general disappointment with the results of the explosion.” See David Holloway, Stalin and the Bomb: The Soviet Union and Nuclear Energy, 1939-1956 (New Haven: Yale University Press, 1994), 227.

[5] . Manhattan District History, Book VIII, Los Alamos Project (Y) – Volume 3, Auxiliary Activities, Chapter 8, Operation Crossroads (n.d., ca. 1946), as cited in Restricted Data: The Nuclear Secrecy Blog.

[6] . Quotations from Barton H. Hacker, The Dragon’s Tail: Radiation Safety in the Manhattan Project, 1942-1946 (Berkeley: University of California Press, 1987), 136-137.

[7] . Ibid, 138 and 140.

[8] . Schwartz, Atomic Audit, 405-406.

[9] . Weisgall, Operation Crossroads, 107-108.

[10] . Martin Sherwin and Kai Bird, American Prometheus, 332, 350.

[11] . A subsequent public statement indicated Joliot-Curie’s distress over the Smyth report.

[12] . Additional intelligence information was gathered from Alexandrov. According to a

message to Secretary of State Brynes from Fred Searls, a member of the U.S. delegation to the United Nations Atomic Energy Commission, “intelligence reports of declarations by Alexandrov at Bikini” indicated that the Soviets lacked “workable high-grade deposits” of uranium.

[13]. Leffler, A Preponderance of Power, 114-116.

[14]. Robert S. Norris, Racing for the Bomb: General Leslie R. Groves, the Manhattan Project’s Indispensable Man (South Royalton, VT: Steerforth Press, 2002), 673, note 32.

[15] . Weisgall, Operation Crossroads, 233.

[16] . Hacker, The Dragon’s Tail, 145-146.

[17] According to the Defense Nuclear Agency report, report on , Warren did not have direct evidence about plutonium particles but “indirect evidence” convinced him of the danger. Thus, it was “prudent and conservative” to decide to bring decontamination work to a halt. See pages 116 and 118.

[18] . That several Soviet officials had witnessed a U.S. nuclear test gave them considerable standing. Beria did not want any slip-ups in the first Soviet test and insisted that the scientists replicate the U.S. “Fat Man” design. Immediately after they staged their initial test, “First Lightening” in August 1949, Beria reportedly called Mescheryakov and asked him, “Was it similar to the American one? Very? We didn’t muff it? … Everything was the same? Good. That means we can inform Stalin that the test took place successfully.” See Gordin, Red Cloud at Dawn, at 176.

[19] . For a press account, see “Soviet Already Has Atomic Bomb Ready to Test, Russian Scientist Implies,” The New York Times, 13 August 1946. See also Michael D. Gordin, Red Cloud at Dawn: Truman, Stalin, and the End of the Atomic Monopoly (New York: Farrar, Strauss, and Giroux, 2009), 134-135.

[20]. For Kravchenko and his life before and after his defection, See Gary Kern, The Kravchenko Case: One Man’s War On Stalin (New York: Enigma Books, 2007).

[21] . Hershberg, James B. Conant, 389.