Se UNITED STATES ATOMIC ENERGY COMMISSION WASHINGTON 25, D..C.. December 17, 1953-Honorable Robert LeBaron Chairman, Military Liaison Committee to the Atomic Energy Commission Dear Mr. LeBaron: It is clear that with the entrance of nuclear weapons into the realm of megaton yields, new concepts of civilian defense must be formulated which will prepare civilian defense organizations for the destruction which would follow the detonation of such weapons over any portion of the United States. That this problem was recognized both by the AEC and by the Federal Civil Defense Administration is demonstrated in part by exchange of corresponderce between the Federal Civil Defense Administrator and the Chairman of the AEC (Enclosures 1 and 2)* As requested by the Civil Defense Administrator, a "sanitized" version of the motion picture on Operation Ivy has been prepared for showing before the group of mayors who will be attending the Mayors' Conference sponsored by the White House on December 14 and 15. DOE ARCHIVES The film, a deleted version of the film "Operation Ivy", shows certain of the footage pertaining to the Mike Shot of Operation Ivy. (This film was shown to the Chief of AFSWP and his staff on November 25, 1953.) Ail information which would give éeny indication as to the nature of the thermonuclear reaction, tnecluding ic¢entity of reactants, or the manner in which the rezetion is brought about, has been deleted from the film leaving only the clear indication that the detonation was that of a thermonuclear device. While all specific mention of the yield of Ivy Mike has been deleted from the film, sufficient information remains to permit calculation of an approximate yield by a technically qualified person. This information has been allowed to remain in the modified version since to remove it would destroy the usefulness of the film. . The Commission has determined that declassification of the yield of the Mike device, Operation Ivy, to this extent will not adversely affect the common defense and security. It does not give any indication as to how such a device is designed or built or any indication as to how it operates. Moreover, the yield of Mike is well within that which our foremost scientists have often openly discussed as being possible (e.g. "a thousand times more powerful than the Hiroshima bomb" -- H. A. Bethe). In addition, the observed yield of any particular device does not in any way imply that such a device is the most powerful or least Secretariat Note: *Circulated as AEC 413/16 ~ vac %- Saniy Gena Se te oe TREE mete oe = ft = sa re hE eh . = AAT A oie, atria eee Te az : : PR=~Q3:02,,-38 § legs OU Sa “S a Se \ Ads