60th Anniversary of Castle BRAVO Nuclear Test, the Worst Nuclear Test in U.S. History

Blast Had Far Greater Explosive Yield than Expected, Equivalent to 1,000 Hiroshimas

Fallout from the Test Contaminated the Marshall Islands and Japanese Fishermen on the Fortunate Dragon (Fukuryu Maru)

Consequences of BRAVO Created Outrage around the World and Pressure to Ban Nuclear Weapons Tests

National Security Archive Electronic Briefing Book No. 459

Posted - February 28, 2014

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

Washington, D.C., February 28, 2014 – Sixty years ago, on 1 March 1954 (28 February on this side of the International Dateline), on Bikini Atoll in the Marshall Islands, the U.S. government staged the largest nuclear test in American history. The BRAVO shot in the Castle thermonuclear test series had an explosive yield of 15 megatons, 1000 times that of the weapon that destroyed Hiroshima and nearly three times the 6 megatons that its planners expected. To recall this shocking event the National Security Archive posts today a selection of documents about the BRAVO shot and its consequences, mainly from State Department records at the National Archives.

The 15-megaton Castle BRAVO nuclear test, 1 March 1954, created a crater a mile wide and spread radioactive fallout around the world. The mushroom cloud rose to 130,000 feet and broadened to more than 25 miles in diameter. Excerpt from U.S. Air Force documentary film, Joint Task Force 7 Commander's Report, Operation Castle.

Castle BRAVO spewed radioactive fallout around the world and gravely sickened nearby inhabitants of the Marshall Islands, then under a U.S. trusteeship, and 236 were evacuated as well as 28 American military personnel on a nearby island. Twenty-three Japanese fishermen were also contaminated, which made the test known to the world and roiled U.S-Japanese relations. While the U.S. government claimed at the time that a shift in the wind spread the fallout far from the test site, a recent U.S. government report demonstrates that it was the volcanic nature of the explosion that dumped the fallout nearby. The adverse health effects for inhabitants of Rangelop Atoll, 110 miles away from the test site, were severe and some islands remained uninhabitable for years. This radiological calamity had a significant impact on world opinion and helped spark the movement for a nuclear test moratorium which ultimately led to the 1963 Limited Test Ban Treaty.

Included in this posting is a U.S. Air Force documentary film on the Joint Task Force 7 commander's report on the Castle Series. It includes footage of the BRAVO shot as well as coverage of the evacuation of U.S. personnel and Marshall Islanders in the wake of the test. The documentary is sanitized at points apparently to protect nuclear weapons design information. A Freedom of Information request by the Archive for a fresh review and a subsequent appeal failed to dislodge more details.

Documents in this posting include:

  • Japanese government accounts of the Fukuryu Maru incident
  • The May 1954 petition by Marshall Islanders for an end to nuclear tests in the area
  • U.S. Embassy Tokyo telegrams on BRAVO's adverse impact for U.S.-Japanese relations
  • Internal U.S. government consideration of compensation to the Japanese government and the Marshall Islands for losses incurred by nuclear testing
  • Decisions to delay the return of the inhabitants to Rongelap Atoll because of unsafe conditions
  • A comprehensive Defense Threat Reduction Agency report from 2013 on Castle BRAVO exposing "legends and lore" about the test

Source: Document 17: Thomas Kunkle and Bryon Ristvet, Castle Bravo: Fifty Years of Legend and Lore: A Guide to Offsite Radiation Exposure, page 35

Source: Document 17: Thomas Kunkle and Bryon Ristvet, Castle Bravo: Fifty Years of Legend and Lore: A Guide to Offsite Radiation Exposure, page 5.

The scene of the extraordinary Eisenhower-Strauss press conference at the Old Executive Office Building (since renamed after Eisenhower) on 31 March 1954. For the full transcript and an audio recording of the event from the Dwight D. Eisenhower Presidential Library, go to document 16. Listen to this clip from the recording where Strauss answered questions about the effectiveness of the Castle Bravo blast, saying that the H-bomb could "take out a city" (Photo from Wikipedia ).

Why and how exactly U.S. scientists miscalculated the yield remains classified but what made the 15-megaton Bravo shot the worst nuclear test in U.S. history is no secret. The device detonated on an islet in a coral reef, producing massive levels of fallout that quickly reached the stratosphere before falling to earth. It is worth comparing BRAVO to the most powerful nuclear test ever, the Soviet Union's 50-megaton "Tsar Bomba" of 30 October 1961. That test's radiological consequences were far less severe because the "Tsar Bomba's" fireball never touched the earth's surface producing significantly less fallout than BRAVO. Historian of science Alex Wellerstein has written that Castle BRAVO is a "cautionary tale about hubris and incompetence in the nuclear age — scientists setting off a weapon whose size they did not know, whose effects they did not correctly forecast, whose legacy will not soon be outlived."[1]

While the "Tsar Bomba" was almost immediately known to the world, the architects of the Castle test series worked in secrecy; the Eisenhower administration wanted to keep words like "hydrogen" and "thermonuclear" out of public discourse and only the fact that tests would be held in the Pacific in 1954 went to the public. After the BRAVO shot occurred, the AEC and the Defense Department sought to control what could be known about the event. But the cat was out of the bag when the Fukuryu Maru crew returned to port which gave Washington a serious damage control problem as information about the 1 March test began to reach the public. At the end of the month AEC chairman Lewis Strauss gave a generally misleading press conference about BRAVO but he managed to alarm the public when he acknowledged that hydrogen bombs could be "made large enough to take out a city … any city."[2]

Until recently, an extensive collection of documents on nuclear testing in the Marshall Islands was readily available on a Department of Energy Web site, The Marshall Islands Document Collection. It no longer has an on-line presence. In the fall of 2013, at the time of the U.S. government shut-down, this important collection disappeared from the Web. It is unclear whether the Department intends to restore it as a distinct Web page. Many documents on the Marshall Islands can be found on the Energy Department's OpenNet but whether they are essentially the same items is also unclear at present. Moreover other documents on nuclear testing in the Marshall Islands that the Energy Department declassified in the 1990s and were once available at the National Archives or on-line were reclassified early in the last decade after the Kyl-Lott amendment went into effect in 1999.[3]

Unique non-U.S. government documents about the consequences of nuclear testing in the Marshall Islands are also at risk. The case files of the Nuclear Claims Tribunal for the Marshall Islands, which went out of existence in 2010, are an irreplaceable record of the impact of nuclear testing on a vulnerable population. The collection of paper records resides in a building in Majuro, the Marshall Island's capital city, but no arrangements are in place to assure their long-term preservation.[4]



Sources information: Unless otherwise noted, all documents in this collection are from the State Department's central decimal files, 1950-54, at the National Archives. Documents are from two decimal files, 711.5611 or 211.9441. Other important documents can be found in the U.S. Department of State, Foreign Relations of the United States, 1952-1954,Volume XIV Part 2:Japan (Washington D.C.: Government Printing Office, 1985).

Document 1: U.S. Air Force Lookout Mountain Laboratory, Joint Task Force 7 Documentary Film, "Operation Castle Commander's Report," n.d., Sanitized copy

Source: FOIA request to Department of Energy processed by Sandia National Laboratories Video Services

This film, posted previously on other Web sites, covers the Castle nuclear test series, consisting of six detonations during 1 March-14 May 1954. It represents the report of the commander of Joint Task Force 7, which carried out nuclear tests during the period. Because of security concerns, the Department of Energy excised all coverage of the third shot, Koon, on 6 April 1954 (which was a fizzle). Produced for military planners and senior U.S. government officials, the film depicts the elaborate preparations for the test, including the extensive array of diagnostic equipment used to measure the detonations and gauge their effects. Despite the excisions, the film conveys that U.S. nuclear planners found the test series valuable for understanding fallout effects and for future military planning. Castle further demonstrated that it was possible to field megaton-class nuclear weapons that weighed less than 10,000 pounds. Thus, the narrator found the Castle tests were "vital" for U.S. national security.

Note: Thanks to Howie Southard, George Washington University Academic Technologies, for converting the film into digital format.


Document 2: State Department Office of Legal Affairs, Memorandum of Conversation, "Injury to Japanese Fisherman by the Bikini Explosion," 17 March 1954, Secret

When the Fukuryu Maru returned to port at Yaizu on 14 March, the secret of Castle BRAVO was out. The Japanese government informed Washington about the condition of the crew and State Department and Atomic Energy Commission officials immediately began discussions of liability issues, probable Japanese claims, and ways and means for compensation. After some consideration of using emergency funds available to the State Department and the White House, it became evident that the Bureau of the Budget would play a central role in making recommendations for compensation.


Document 3: State Department telegram 2090, 19 March 1954, Unclassified

Despite the claims by Atomic Energy Commission chairman Lewis Strauss, the Fukuryu Maru was operating 14 miles outside the 57,000 square mile "Danger Area" established by the U.S. Navy around the test site. The crew had no warning that a test was imminent and U.S. radar and spotter planes did not detect the ship. The "Danger Area" had nothing to do with health and safety; instead it was a security zone "to deny information to enemy nations." After the Fukuryu Maru incident became known, the U.S. Commander-in-Chief Pacific created a massive danger zone of 570,000 square miles, which raised serious problems for the Japanese fishing industry.[5]


Documents 4A-C: U.S. Embassy Telegrams on the Crisis in U.S.-Japan Relations:

A: U.S. Embassy Tokyo telegram 2261, 21 March 1954, Secret

B: U.S. Embassy Tokyo telegram 2264, 22 March 1954, Secret

C: U.S. Embassy Tokyo telegram 2279, 23 March 1954, Secret

Deep Japanese aversion to nuclear weapons and the Fukuryu Maru crew's precarious health created serious difficulties for U.S.-Japan relations. Supporting compensation for the damage done to the fisheries and the Maru's crew, Ambassador John M. Allison recognized that the Japanese government was in a difficult position, facing as it did questions about the United States closing off areas of the Pacific and the impact on the fishing industry. Perhaps not sufficiently appreciating the Japanese Government's difficulty and the U.S. responsibility for the crisis, the Embassy reports were critical of Tokyo for a perceived lack of cooperation.. Sensitive data on radioactive fallout had reached the Japanese press, the press was "fanning extreme emotionalism," and Japanese Communists were trying to capitalize on the affair. Besides an "irresponsible" attitude on security, the Embassy also saw bureaucratic rivalries and "resentment" of Japanese scientists toward the United States complicating the problem.


Document 5: Letter from Mrs. Tamaki Uemura, President of the Japanese Young Women's Christian Association, to Mrs. Mamie Eisenhower, 30 April 1954, Unclassified

After Japanese doctors had issued public reports about the deteriorating health of the fishermen and had publicly requested information on treatment to remove radioactive strontium 90 from bone marrow, angry U.S. Embassy officials demanded that the Government correct the statements, which suggested that the U.S. had been less than cooperative. In the wake of this incident, YWCA president Uemura publicly protested to the president's wife, Mamie Eisenhower, asking why the U.S. government had questioned the doctor's statements, suggesting a lack of understanding about Japanese thinking about the horrors of radiation sickness. Uemura highlighted the serious damage the tests had inflicted on the fishing industry because fish was a "must item" in the Japanese diet.[6]


Document 6: U.S. Embassy Tokyo Airgram 1481, "Transmittal of Preliminary Report of Dr. Merrill Eisenbud - 'Contamination of the Fukuryu Maru and Associated Problems in Japan,'" 30 April 1954, Confidential

Merrrill Eisenbud, the AEC's first health and safety chief, arrived in Tokyo on 22 March to investigate the irradiation of the ship, the cargo, and tuna catches, but also to offer technical support, mainly on radiological issues, to the Japanese scientists and doctors treating the crew. The Atomic Bomb Casualties Commission's Dr. John Morton had already offered assistance on treatment of the patients. Eisenbud's report cited the "uncooperative atmosphere" that he encountered, such as Morton's inability to get access to most of the patients and the general refusal of the Japanese to provide access to all but small portions of the radioactive ash that had been collected. Not mentioned, however, is that, for security reasons, the U.S. specialists would not provide Japanese doctors with information they wanted about the composition of the radioactive ashes.[7]

Eisenbud's preliminary report reviewed issues that he believed needed further exploration, including the degree of dangerous beta and gamma radiation that the fisherman had received from the fallout. Noting estimates that exposure had been in the range of 70 Roentgens, Eisenbud believed that the "actual dose could have been 2, 10, or even a 100 times higher." Later research indicated that the crew had been exposed to 290 roentgens, whereas 3.9 was the maximum allowable exposure for AEC personnel.[8]


Document 7: U.S. Embassy Tokyo Airgram 1482, "Public and Private Official Papers Relating to the Case of the Fukuryu Maru No. 5: Documentation March 17-April 23 1954," 30 April 1954, Secret, excerpts

This airgram is a compilation, with a detailed summary, of communications between the U.S. and Japanese governments during the first weeks of the crisis. Included is the Maritime Safety Agency's initial report on the Fukuryu Maru incident as well as more detailed accounts of what happened to the crew on 1 March and during the return voyage to Japan. In light of concern among some U.S. officials that a hidden "Red" hand had played a role in the incident, the compilation includes a list of U.S. Embassy questions to the Japanese about the crew members' political affiliations, whether they listened to Communist radio stations, or whether any of their relatives had Communist affiliations. The Foreign Ministry's answers are included; not surprisingly, it discovered no Communist connections to the fishermen


Document 8: Admiral Arthur Radford, Chairman, Joint Chiefs of Staff, Memorandum to Secretary of Defense, "A Proposal for a Moratorium on Future Testing of Nuclear Weapons," 30 April 1954, Secret

Castle Bravo and its consequences sparked antinuclear protests around the world, with Indian Prime Minister Jawaharlal Nehru calling for a "standstill agreement" on nuclear tests.[9] The Joint Chiefs of Staff quickly rejected proposals for a moratorium arguing that with the U.S. already enjoying an "indeterminate advantage" over the Soviet Union in nuclear weapons technology, a moratorium would provide Moscow with the opportunity to "neutralize" the U.S. advantage by abrogating or violating an agreement. While a moratorium might be politically advantageous for Washington, the advantages would be fleeting "whereas the military disadvantages would be far-reaching."


Document 9: U.S. Embassy Tokyo Telegram 2702, 4 May 1954, Secret

The U.S. Embassy reported that the Japanese Foreign Ministry had sent a note trying to explain why the Japanese reaction to the incident had been unfavorable to the United States and why Tokyo had found itself in an "embarrassing" position during the crisis. For example, information on the composition of the fallout had been reported publicly because Japan had no atomic secrecy regulations and U.S. doctors had not received full access to the patients because of the latters' concern that they would be seen as "experimental material rather than as a therapeutic object." The Embassy rejected the latter claim but agreed that the Government had cut "a poor figure" during the crisis.


Documents 10A-B: The Marshall Islands Petition

A: U.S. Mission to the United Nations Despatch 790, (UN-UND) Petition from the Marshallese People Concerning the Trust Territory of the Pacific Islands," 4 May 1954, Unclassified

B: State Department telegram 543, "Re: Marshallese Petition," 4 May 1954, Official Use Only

On 20 April, representatives of the Congress of the Marshall Islands filed a petition with the United Nations. Citing the "increasing danger" from U.S. nuclear tests in the area and the suffering of the people of Rongelap and Uterik, the petition declared that land and access to it were the basis of the "very life of the people." Therefore, the petitioners asked for a halt to nuclear testing in the area, but if that was not possible, for the United States to take "all possible precautionary measures" and to provide safety instruction for the inhabitants and compensation for losses. A response prepared by the AEC and the State Department conceded the suggestions were "eminently reasonable" but also claimed the nuclear tests were in the "interests of general peace and security" and that the Marshall Islanders "had no medical reason to expect any permanent after-effects on the general health of the inhabitants."


Document 11: State Department Instruction A-836, "Estimate of Present Medical Status of the Twenty-Three Crewmen of the FUKURYU MARU," 8 May 1954, Confidential

The Department sent the Embassy in Tokyo a recent report from the AEC's Division of Biology and Medicine based on urine samples of some of the crew and blood counts provided by the Japanese. The news was bad: the urine samples showed that radioactive material had been "ingested" and the low white blood cell counts of the "most seriously affected patients" made it "unwise to assume at this point that all will recover." A draft statement on the possible death of a crew member was being prepared. A copy of the AEC report was being made available to the Joint Committee on Atomic Energy which had been asked to keep the information under wraps because publicity would have "unfavorable repercussions."


Document 12: State Department Memorandum of Conversation, "Radioactive Tuna," 6 July 1954, Confidential

A Food and Drug Administration official reported to the State Department that a West Coast cannery had discovered three radioactive tuna imported from Japan since 1 March. The tuna had probably eaten contaminated fish because the skull and bones of the fish were radioactive. For the time being, to keep the information under control the Department would not inform the Embassy in Tokyo and presumably Japanese diplomats would not be told either.


Document 13: U.S. Embassy Tokyo telegram 207, 26 July 1954, Confidential

Ambassador Allison reported that Prime Minister Yoshida had almost been persuaded to request a $4.2 million compensation claim but that the Foreign Ministry had talked the number down to $1 million. Allison favored a quick settlement to avoid adverse publicity, but it took months to finalize, even after one of the crew members, Aikichi Kuboyama, died in September from liver ailments possibly aggravated by the radioactive exposure. The U.S. government gave his widow a check for 1 million yen ($2,800) and in January 1955 it paid the Japanese government $2 million in compensation for losses caused by BRAVO and other tests.[10]


Document 14: Letter, James J. Wadsworth, Deputy U.S. Ambassador to the United Nations, to David W. Wainhouse, Acting Assistant Secretary of State, 4 August 1954, Official Use Only

Wadsworth recounted a recent memorandum from Mason Sears, the U.S. Representative to the United Nations Trusteeship Council, to Ambassador to the United Nations Henry Cabot Lodge about the diplomatic risks posed by the post-BRAVO situation. Noting that India's representative to the UN Khrishna Menon had raised questions about the legality of nuclear testing in UN trust territories, Sears argued that Washington would have trouble getting the support of close allies if another BRAVO incident occurred. Moreover, Washington had to move forward on the matter of compensation; the claims of the Bikinians remained unresolved and "just and prompt settlements" for the former residents of Rongelap and Uterik were also necessary.


Document 15: U.S. Embassy Tokyo Telegram 849, 8 October 1954, Confidential

Tokyo kept up the pressure on Washington on various fronts. A note from the foreign minister requested the United States to move its nuclear testing grounds as far away as possible but if that could not be done, to reduce the size of the tests. The matter of compensation to the Japanese fishing industry for damage caused by nuclear testing also remained on Tokyo's agenda.


Document 16: Letter, Chairman Atomic Energy Commission Lewis Strauss to Secretary of State John Foster Dulles, 2 December 1954, with Memorandum from Gerard C. Smith attached, 13 December 1954, Confidential

Taking into account Sears' argument for compensation [see document 14] Lewis Strauss described the state of play in this letter to the secretary of state. A lump sum payment was in the works for the Bikinians who had been displaced in 1946. Strauss misleadingly claimed that people on Rongelap and Uterik had been evacuated "immediately" after the test, but that did not occur until two days later, after huge amounts of radioactive debris had fallen on the atolls. With respect to their claims, the Defense Department would handle them but they had to be filed within a year of incident. The people on Uterik had been returned to their homes, but the Rongelap people would not be returned until May 1955.

Bikini's former inhabitants received compensation in 1956, but it was not until the mid-1960s that the U.S. government provided any compensation for victims of the BRAVO exposures. It took another 24 years for Washington to establish a trust fund for the Marshall Islands.


Documents 17A-B: Postponed Return to Rongelap Atoll

A: Office of Special Assistant to Secretary of State for Atomic Energy Matters, Memorandum of conversation, Return of Inhabitants to Rongelap," 22 April 1955, Official Use Only

B: Office of Special Assistant to Secretary of State for Atomic Energy Matters, Memorandum of conversation, Return of Inhabitants to Rongelap Atoll in the TTPI," 18 May 1955, Official Use Only

Source: National Archives, Record Group 59, Records of the Special Assistant to the Secretary of State for Atomic Energy and Outer Space, General Records Relating to Atomic Energy Matters, 1948-1962, box 424, 18. Weapons 4. Marshall Islands, 1954 - 1956

Strauss's hope for a return to Rongelap atoll by May 1955 was excessively optimistic. By April and May, discussions between AEC and State Department officials indicated that immediate return was impossible. The first conversation indicated serious problems: people could go back to the atoll as long as they "restrict" themselves to the southern islands and "do not eat too many shellfish." But in mid-May, Deputy High Commissioner for the Pacific Islands Trust Territory Delmas Henry Nucker decided that it "would still be dangerous to the inhabitants, as would the shell fish in the lagoon." It would take "another year" before the atoll was "completely safe for the people to return." In 1957, people returned to Rongelap, but the area remained seriously contaminated. Controversy over the actual impact of the radiation persisted, but growing concern about the degree of hazard led the people on Rongelap to vote with their feet. In 1985 Greenpeace's Rainbow Warrior transferred over 300 people from Rongelap to Majetto, an island in the Kwajalein Atoll.[11]


Document 18: Thomas Kunkle and Bryon Ristvet, Castle Bravo: Fifty Years of Legend and Lore: A Guide to Offsite Radiation Exposure (Defense Threat Reduction Agency, Defense Threat Reduction Information Analysis Center, January 2013), DTRIAC SR 12-001

Source: Restricted Data Blog

This comprehensive work on the BRAVO shot was written for a highly specialized audience, although the fine selection of photographs will interest a wider audience. The report's purpose is to explain exactly how local populations in the Marshall Islands were exposed to dangerous levels of fallout. That the MIKE thermonuclear test in late 1952 had produced relatively small amounts of fallout provided a "misleading lesson" which encouraged the Castle planners to believe the tests could be conducted without advance evacuation of nearby populations. A central element of the BRAVO disaster was that the device exploded on the surface of Bikini atoll with the resulting fireball "suck[ing] up…ten million tons of pulverized coral debris coated [with] radioactive fission products." Like a volcanic eruption, BRAVO "injected a great mass of debris into the stratosphere" which rapidly fell to the earth. With this the authors laid to rest the "legend" that unanticipated shifts in the wind led to the fallout on Rongelap [See document 10B for an example]. While the report challenges claims that radioactive exposure was responsible for thyroid problems among the Marshallese, it includes this sobering conclusion: "It is clear beyond doubt that the people evacuated from Rongelap, especially the children, have suffered medically from their fallout radiation exposure" [p. 120].



[1] See Wellerstein's analysis, "Castle Bravo Revisited" at Restricted Data: The Nuclear Secrecy Blog.

[2] Lawrence Wittner, The Struggle Against the Bomb, Volume II: Resisting the Bomb: A History of the World Nuclear Disarmament Movement, 1954-1970 (Stanford: Stanford University Press, 1993), 2-3; Barton Hacker , Elements of Controversy: The Atomic Energy Commission and Radiation Safety in Nuclear Weapons Testing, 1947-1974 (Berkeley: University of California Press, 1994), 136, 138.

[3] April L. Brown, "No Promised Land: The Shared Legacy of the Castle Bravo Nuclear Test," Arms Control Today https://www.armscontrol.org/ac/ March 2014, 43. This article includes a useful map of the Marshall Islands.

[4] Information from Trudy Huskamp Peterson, e-mailed 20 February 2014.

[5] Martha Smith-Norris, "'Only as Dust in the Face of the Wind,': An Analysis of the BRAVO Nuclear Incident in the Pacific, 1954," Journal of American-East Asian Relations 6 (1997): 1-34, (danger zone discussed at 13-14). This highly useful assessment should be supplemented by Roger Dingman's account of the Fukuryu Maru incident, "Alliance in Crisis: The Lucky Dragon Incident and Japanese-American Relations," in Warren I.Cohen and Akira Iriye, The Great Powers in East Asia, 1953-1960 (New York: Columbia University Press, 1990): 187-214. For the "Danger Area," see also document 17 at page 88. Very important on radiological matters is Hacker, Elements of Controversy, 130-158. See also Toshihiro Higuchi's important book, Political Fallout: Nuclear Weapons Testing and the Making of a Global Environmental Crisis (Stanford: Stanford University Press, 2020).

[6] Smith-Norris, "Only As Dust in the Face of the Wind," 21-22.

[7] Dingman, "Alliance in Crisis," 38-39.

[8] Smith-Norris, "Only As Dust in the Face of the Wind," 9; Hacker, Elements of Controversy, 85.

[9] Wittner, The Struggle Against the Bomb, 1-28, 98-99.

[10] Smith-Norris, "Only As Dust in the Face of the Wind," 21-22

[11] For a run-down on the history of the claims settlement, see Arjun Makhijani and Stephen I. Schwartz, "Victims of the Bomb," in Stephen I. Schwartz et al., Atomic Audit: The Costs and Consequences of the U.S. Nuclear Weapons Program, 1940-1998 (Washington, D.C. : Brookings Institution, 1998), 415-421.