Letter to the President, Subject: Att'd Extracted Version of the Final Report of the JCS Evaluation Board on Operation Crossroads " the Evaluation of the Atomic Bomb as a Military Weapon " 6/30/47

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s BEST AVAILABLE COPY THE SECRETARY OF DEFENSE I y *L There is forwarded herewith for your information, an extracted version of the Final Report of the Joint Chiefs of Staff Evaluation Board on Operation CROSSROADS. It is identical with the Board’s complete report, except for deletions made by the Board itself in the interests of national security. From a purely military standpoint, the Joint Chiefs of Staff consider this version to be suitable for release to the public, and with this in mind have prepared the attached proposed release. At the same time, however, they have emphasised that there were non-military considerations which should be taken into account before making a final decision to publicize all or any portion of it. They have also indicated, by red lining certain portions of the report, various specific statements which might be considered for deletion on non-military grounds in the event that general publication is contemplated. These marked portions relate prin cipally to two important Recommendations of the Board. The first concerns the enactment of legislation which would establish new definitions of acts of aggression and incipient attack. Such legislation would make it the duty of the President of the United States, as Commander-in-Chiaf of its Armed Forces, and after consultation with the Cabinet, to order atomic bomb retaliation when such retaliation was necessary to prevent or frustrate an atomic energy attack upon us. The second recommendation has to do with possible revisions in the Atomic Energy Act of 1946 in order /to provide Service representation on the Commission, to place the ^ownership and control of fabricated atomic weapons in the Armed Forces, and to give the Services greater participation and control in the designing and testing of such weapons, and in the handling of information relating to their military utilization. The question of releasing this report, either with or without the deletion of the red lined portions, has been extensively considered by myself and the members of the War Council. In addition, I have discussed the matter with the Secretary and Under Secretary of State. The latter strongly recommend against any release at this time unless there are compelling affirmative OSD letter, April U, 1974

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HXKRY S. TRUMAN LIBRARY BEST AVAILABLE COPY reasons for doing so. They also urge, if a release is to be made, that the red lined portions of the report should be deleted. They believe that public disclosure of the report at this time might be misinterpreted both here and abroad, and considered as a preface to some brusque action which we do not, in fact, intend. In the light of these State Department views, I forward this document with the recommendation that it not be released at this time. In doing so, however, I feel obliged to call your attention to the correspondence between Dr. Earl Compton, Chairman of the * Evaluation Board, and Admiral Leahy on this subject. Dr. Compton's letter points out certain contrary considerations which are involved, although in the end he concludes that no release of the Board's findings, as such, is necessary. However, he, and the other members of the group, reserve their rights, as private individuals, to express their own personal opinions on the subjects The White House BEST AVAILABLE COPY

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BEST AVAILABCE COPY THE EVALUATION of the ATOMIC BOMB The Final Report Joint Chiefs of Staff OSD Utter, April 12, 1974 THE DIVISION OF CLASSIFICATION, O.S. ENEHGT BESFAHCH AND DEVELOPMENT ADMINISTRATION, HAS DETERMINED THAT THIS DOCUMENT CONTAINS MO RESTRICTED DATA OR FORMERLY RESTRICTED DATA. ERDA HAS HO OBJECTION TO ITS DECLASSIFICATION. BEST AVAILABLE COPY

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The following pages contain the salient portions of the final report of the Joint Chiefs of Staff Evaluation Board. The Beard has seen fit, in the national interest, to delete certain paragraphs. Other deletions have been made by competent authority in accordance with the provisions of the ATOMIC ENEIIOY ACT. The Joint Chiefs of Staff have rxado further deletions in the interest,of security of military data derived from the Crossroads tests, (or otherwise in the national interest at the request of higher authority).* •K- This clause to be added, or some suitable equivalent, in case the. President wishes the bracketed paragraphs to bo deleted. BEST AVAILABLE COPY

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BEST AVAILABLE COPY HARRY S. TRUMAN LIBRARY JOINT CHIEFS OF STAFF EVALUATION BOARD Vice Admiral John H. Hoover, USN Rear Admiral Ralph A. Ofstie, USN Secretary to the Board Acting Secretary to the Board Col. Robert G. Butler, USA Moj. Glen W. Clark, USA, !- Technical Aids to the Board BEST AVAILABLE COPY Enclosure "A"

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TABLE OP CONTENTS PART I - LETTER OF TRANSMITTAL............................................................... 7 PART II - BOARD'S PARTICIPATION IN THE TESTS............................. 8 PART III - CONCLUSIONS AND RECOMMENDATIONS Section One - CONCLUSIONS............................................................ 10 Section Two - REGOMMENDATIONS................................................... Ip PART IV - TEXT OP THE REPORT Section One - OPERATION CROSSROADS....................................... 16 Section Two - GENERAL PHENOMENA.............................................. 18 Section Three - EFFECTS UPON SHIPS One - Damage Results................................................................. 18 Two - Naval Design and Training....................................... 20 Section Four - EFFECTS UPON THE HUMAN ORGANISM.......... 21 Section Five - USE OF BOMB IN WAR One - General Defense Considerations............... Two - Research, Development and Stockpiling Three - Measures of Active Defense.................... Six - Consideration of Targets............................. Seven - Effectiveness of the Bomb Eight - Psychological Atomic Warfare............... Nine - Continuous Review of Targets................. Ten - Concluding Observations................................ must be corrected accordingly. page numbers BEST AVAILABLE COPY

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BEST AVAILABLE COPY In the preparation of this report the Board availed itself of the services of Rear Admiral \!% S. Parsons, USN, Chairman, JOIN!' CROSSROADS COMMITTEE and found his advice and assistance of groat value. In addition, momhors of the Operations Evaluation Group, Office of the Chief of Naval Operations, were of service to the Board. Its members arc Director of JOINT CROSSROADS COMMITTEEj to Dr. Arthur Brown, of the OEG; and Commander Roger Rovelie, USER, Oceanographic Assistant to the Director of Ship Material and Co-ordinator for Oceanography to the JOINT CROSSROADS COMMITTEE, for material espocicily prepared for this report. Rear Admiral T. A. Solberg, USN, Director of Ship Material and Capfc. tc\ the Board in his field. Credit for material taken from the reports of others Is contained in the text of this report. BEST AVAILABLE COPY

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BEST AVAILABLE COPY This report v.o.s nr op ere cl uncor the direction of the Board hy Mi*. Russ Symontowne, ExpertConcultcnt to the Civilian Members of tho Boera and Chief of its Secretariat, Mr. Symonto'wno had the assistance of Dr, Thornton Pago, Clerk, USA, Technical Aids and Consultants to the Military and Naval Members of the Board. BEST AVAILABLE COPY

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BEST AVAILABLE COPY HARRY S. TRUMAN LIBRARY PART I -- Letter of Transmittal The Joint Chiefs of Staff Subject: Final Report, JCS Evaluation Board \ Your Board, appointed to evaluate tho Bikini Atoll Atomic Bomb tests, has the honor to transmit to you its final In accordance with our Directive this report is fled as a TOP SECRET, In order that the Joint Chiefs may moke this report public, the Board has prepared a from which certain matter has been deleted. Prior to re vis ion lication of this r^v factual material be Wo regret the ision it will be necessary that classified deleted by the Joint Chiefs of Staff. death of Gon. Joseph W. Stilwoll, an original member of the Board, who took an ■ ctivo part in its er.rly deliberations. His duties hove been capably discharged l^y Lieut. Gen, A, C, Wedemeyor, whom you appointed to succeed Thomas F. Farrell Karl. T. Compton, Chairman Vice Adm. John H. Hoover, USN BEST AVAILABLE COPY

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BEST AVAILABLE COPY HARRY S. TRUMAN LIBRARY 1. Under date of 27 February 19^6, William D. Leahy, Fleet Admiral, United States Navy, Chief of Staff to the Commander in Chief of the Army and Navy transmitted a memorandum for the Chairman, Evaluation Board, Atomic Bomb Tests with the subject: "instructions to Evaluation Board, for the Atomic This memorandum charged the Board with "two broad, "a. To be available for advice to the Task Force Com mander during the preparations for the tests. "b. To examine and evaluate for the Joint Chiefs of Staff the results of the tests. 2. There followed instructions for the preparation of two preliminary, public reports, one to be submitted immediately upon the conclusion of each test. /j. Concerning its final report this memorandum informed the Bo^rd that it should include "pertinent comments on strategy, tacNiios, and technical information valuable to the national interests of the United States", 4. The memorandum further read: "The Evaluation Board will be guided exclusively by its own judgment in its evaluations based on the results of the tests. Particular attention will be paid In the final evaluation to the strategic implications of the results as well as the factual damage Incurred by naval vessels and other material". 5. The Chairman, acting on behalf of the Board and with its subsequent approval, offered 2 April 1946 several suggestions to the Commander, Joint Task Force One, with respect to the oil, gasoline and ammunition loadings of certain target vessels, as well as to Instrumentation for the tests. The Chairman's observations, together with the reply of the Task Force Com mander have been presented previously.

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BEST AVAILABLE COPY HARRY S. TRUMAN LIBRARY .6. The Board held three mootings in Washington, prior to the tests, these being on 23 February, 26 March and 29 April. Its members and staff left Washington for Bikini Atoll 23 June and, after witnessing the tests, returned 1 August. Numerous meetings and consultations with the Task Force Commander, members of his staff and civilian exports were hold during the tests. Tho Board mombors wore afforded every facility for the performance of their duties and enjoyed every courtesy from all with whom they came in contact. _»j 7. Following the tests, tho Board hold throe mootings in Washington for the preparation of this report. These meetings took place 13 and 14 January 19^7, 11 February and 23 April. The Board held its final mooting in Cambridge, Mass., 24 Juno. BEST AVAILABLE COPY

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HARRY S. TRUMAN LIBRARY BEST AVAILABLE COPY PART III -- Conclusions and Rocomondations Section One - CONCLUSIONS Noto: Several paragraphs have been deleted and the paragraph nunbers adjusted accordingly. 1. The Board has reached the following najor conclusions: (1) If used in numbers, atomic bombs not only can nullify any nation's military effort, but can demolish its social and economic structures and prevent their reestablishment for long periods of time. With such weapons, especially if em ployed in conjunction with other weapons of mass destruction as, for example, pathogenic bacteria, it is quite possible tqt,^ depopulate vast areas of tho earth's surface, leaving only vestigial remnants of man's material works. (2) The threat of the uncontrolled use of the atomic bomb and of other weapons of mass destruction is a threat to man kind and to civilization. Only the outlawing of all war and the setting up of an adequate international control of weapons of mass destruction can lift this threat from the peoples of (p) In tho absence of absolute guarantees of abiding peoce, \ the United States has no alternative but to continue the manufacture and stockpiling of weapons of nuclear fission and to carry on continuous research and development for,their im provement and improvement in the means of their delivery. (4) The value of surprise in attack has increased with every Increase In tho potency of weapons. With tho advent of the. atomic bomb, surprise has achieved supreme value so that an aggressor, striking suddenly and unexpectedly with a number of atomic bombs might, in the first assault upon his vital targets, achieve such an order of advantage as would insure tho ultimate defeat of an initially stronger -adversary. (5) There must be national recognition of the probability of surprise attack and a consequential revision of our tra ditional attitudes toward what constitute acts of aggression iso that our armed forces may plan and operate in accordance BEST AVAILABLE COPY Enclosure

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BEST AVAILABLE COPY with the realities of atonic warfare. Our policy of national defense must provide for the employment of every practical means to prevent surprise attack. Offensive measures will bo the only generally effective moans of defense, and tho United (j States nust bo prepared to employ them before a potential enerj !l can inflict significiont damage upon us. r(6) National defonso requirements of tho future are only those of the past; any aggressor must be overcome with superior force. But, whore in the past, tho duty of the ; President, as the Commander in Chief has been restricted (before formal declaration of war) to action only after the loss of American lives and treasure, it must be made his duty I in the future to defend the country against imminent or ?Incipient atonic weapon attack. "incipient" attack it is the responsibility of the Congress to define and to redefine, from tine to tine, so that it nay draft suitable- standing orders to the Commander in Chief for prompt and effective atomic bomb retaliation should another ' nation ready an atonic weapon attack against us. \ (8) No weapon can be more effective than the means used to bring it into action against tho enemy; hence tho necessity for the coordinated dovoionnont of atonic weapons and weaponcarriers and thoir integration into a series of devices, each with a tactical or strategic purpose. In tho category of weapon-carrier may be included any means of ultimate delivery such as aircraft, guided missiles, rockets, torpedoes and nines of all types. TV<40^** (9) Inseparable from the development of bombs and bonbcarrlers, should be- the planning of naval surface and sub marine vessels from which atonic bomb-carriers may be launched or discharged, as well as of land launching devices, stationary or mobile, and tho acquisition and maintenance of land and BEST AVAILABLE COPY

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BEST AVAILABLE COPY HARRY S. TRUMAN LIBRARY ^ (10) Any target study must Include a critical consideration of the vulnerability of this country to atonic bonb attack and should lead to tho study of ways and noans of reducing this vulnerability, not only by physical dispositions and military measures, but by suitable training and indoctrination of military personnel and civilian population. (11) No specific defense against the bonb exists nor, in the current opinion of science, is any likely to be devised. Such passive defense neasurc-s as concealment, or massive shielding, or below-ground construction nay well serve in the case of vital military facilities, but these measures are inpracticable for the defense of a city and its inhabitants. (12) For defense against atomic weapons, chief reliance must be upon the prevention or frustration of an enemy attack, or upon immediate retaliatory measures which will overwhelm an enemy and result In the destruction of his pov-or and ability to mako war. (13) Essential to any plan of defense will be (a) knowledge /as to whether potential onenios are in possession of the means 1 to produce weapons of nuclear fission and (b) jaiowled'«..o of …