INTRODUCTION This concise history of the Air Task Group in Operation CASTLE (the spring 1954 Pacific thermonuclear tests) was produced in the Historical Division, Office of Information Services, Air Force Special Weapons Center by A/1C Dudley F. Saunders. It is not intended to be a complete history of Task Group 7.4 in that operation, but is designed to record the major features of Task Group 7.4's participation, For a full account of Task Group 7.4 in the operation, the reader is referred to the monthly histories of the Air Task Group for the per- é fod beginning July 1953 and ending in May 1954. These monthly reports contain all supporting documents and pictures of the operation. Copies are on file in the AFSWC Historical Archives, the Air Task Group's per= manent records, and with the ARDC Historian. Size and bulk of these histories have made it impractical to distribute copies, since they occupy five linear feet. One additional document completes the Air Task Group history. This is the Final Report of the Commander, Task Group 7.4, Operation CASTLE, ‘Since copies are readily available, no attempt was made to include it in this history. For the same reason, to prevent duplication of effort, documents and photographs included in the monthly Task Group histories were not included in this document. For other reports of the operation, consult the appended bibliography. anu ai Tia.