studies of bomb debris of the constitution and efficiency of nuclear devices detonated by other nations. Nuclear field tests are thus important and integral factors in the diagnostic phases of the over-all weapons research and development program. ‘They are also essential in providing the National Military Establishment and Federal Civil Defense Administration with pertinent information on effects, and for training purposes of many kinds. The acti- vation of an overseas and a continental proving grounds, and the progressing frequency and number of tests, are a direct reflection of the rapid development of atomic weapons during the period. Overseas Tests: Pacific Proving Grounds During the pre-1947 MEDperiod, the first nuclear device was detonated in July 1945, on a remote section of the Alamogordo (New Mexico) Bombing Range. This first, historic test was followed by Operation Crossroads, conducted in July 1946 at Bikini Atoll in the Marshall Islands of the Pacific. The operation consisted of two tests made to determine the effects of atomic weapons against naval vessels. As early as 1947, when the necessity for more tests was apparent, some consideration was given to selecting a testing site within the continental United States. Due to several deterrent factors, the decision was made to continue using the Marshall Islands. scale tests. Pot weed Accordingly, Eniwetok Atoll in the Marshall Islands was approved by the President of the United States on December 2, 1947, as the site for an atomic proving ground en“*trusted to the AEC for operation and maintenance. Its isolated location and more usable real estate influenced its choice over Bikini. Three devices were tested during Operation Sandstone in April 1948. As a result of the Sandstone tests, the efficiency and flexibility of atomic weapons were substantially increased. Construction of permanentfacilities on Eniwetok and Parry Islands began immediately after the operation, and the Pacific Proving Grounds during the present period has served as the overseas site for two series of fullOperation Greenhouse -- Was conducted during April and May 1951. The series con- sisted of four tests: the detonation of two nuclear weapons (bombs) and two experimental devices. The first shot, a weapon test, was detonated April 8 on a 300-foot tower on Runit Island, Eniwetok Atoll. The second shot, also a weapon test, was detonated April 21 ona 300-foot tower on Engebi Island. The third shot, a device test, was detonated May 9 ona 200-foot, heavy-load tower, on Eberiru Island. The concluding shot, also a device, was fired on a 200-foot tower on Engebi Island, May 25. The objectives of the operation were to prove: a weapon of higher yield and efficiency, a weapon of smaller size and weight, and to conduct explorations in the thermonuclear field. In addition, eight experimental programs to study the effects of nuclear detonations on structures, equipment, materiel, and animals were included for the benefit of DOD, AEC Division of Biology and Medicine, and FCDA. Long range detection techniques were further studied during tha Operation Ivy -- Planning was already under way when Greenhouse was concluded. The series was announced on October 1, 1951.° The Ivy series consisted of the detonation of a very high yield thermonuclear device, and a high yield nuclear weapon. Thefirst shot _was detonated on November 1, 1952, from a surface platform on Elugelab Island. The second shot was an air-dropped weapon detonated at a height of 1,500 feet over Runit Island on November 16, 1952. The test contributed significantly to work in the thermonuclear field. Eleven experimental programs were also included in the Operation. = ri) wa SSF "8