Chapter | INTROOUCTION The Armed Forces Special Weapons Project (AFSWP) was informed in April 1952 of plans of the U. S. Atomic Energy Commission (AEC) to conduct a developmental test of highyield weapons at the Eniwetok Proving Ground (EPG) in the fall of 1953 (subsequently deferred to spring of 1954) under the code name Castle (Reference 1). Inasmuch as Operation Ivy —the first test involving high-yicld weapons was then being prepared for conduct in the fail of 1952, no immediate steps were taken by AFSWP to plan for Operation Castle. in August 1352, AFSWP requested the military services to submit preject propesa’s for a military-effect test program for Castle (Reference 2}. On the basis of the proposals submitted, AFSWP presented to the Committee on Atomic Energy of the Research and Development Board on 17 December 1952 an outline for a militaryeffect test program After appropriate discussion (including additional hearings on the long-range -detection program, Program 7, and the shipboard-countermeasures project, Project 6.4), the Research and Development Board approved the program (Reference 3) anc imtiated release to AFSWP of research and development funds (see Section 1.3). 1.1 MILITARY-EF FECT PROGRAM The military-effect program, as approved by the Research and Development Board, was of necessity couched in very general terms. Only preliminary data was as yet available from Operation Ivy, and a firm shot schedule for Castle had not yet been promulgated by che AEC. However, a tentative project list was framed in accordance with the following precepts: (%) Each project must be justified on the basis of a military requirement. (2) Each prceiect must be such that its objectives cannot be attained except by a full-scale test, its objectives cannot be attained at the Nevada Test Site (NTS), and its objectives can be attained at the EPG without unreasonable support requirements. (3) Each project must conform to the shot schedule—-yields, locations, burst heights established for the developmental program of the AEC. In early March 1953, representatives of AFSWP met at Los Alamos with staff members of the J-Division, Los Alamos Scientific Laboratory (LASL) to review compatibility of the desired Department of Defense (DOD) program with the AEC developmental program. Except for non-inclusion of an air burst by the AEC, the programs were generaiiv compatible. As an outgrowth of this meeting, plans for a thermal program (Program 8) under DOD svonsorship were dropped, since LASL agreed to expand its Program 18 to include thermal measurements of particular interest to the DOD; also, a biomedical project involving the exposure of mice to neutron flux was eliminated. During the detailed planning and preparation for the operation, many revisions of project plans were necessitated by changes in shot schedules, detailed analysis of Ivy daca, and support considerationa. However, there was no general revision of project