Only for the first purpose, a proof test, would the detonation necessarily be of a weapon as such. In most circumstances, an ex- perimental device is designed. The device tested is simplified as much as possible to answer the basic question. expenditure of active material. It minimizes the It has as low a yield as possible to minimize off-site fallout. It is seldom a useful weapon design. The information obtained from its testing will, however, immediately or eventually affect the design of gtockpile weapons and improve the stockpile position. The Department of Defense and Armed Forces have a deep interest in the conduct of full-scale tests. Full understanding of the output characteristics of nuclear weapons and their effects on various targets under varying conditions is essential to planning for the use of weapons, for planning military defenses against nuclear weapons, and for developing the desired characteristics of new weapons, The Federal agencies charged with civil defense, biomedical studies, and with non-military applications of atomic energy have a continuing need for effects df#ta paralleling the development of nuclear weapons. Essential civil effects information is generally in two categories, biomedical and structural, both distinct from the military effects data required by the Department of Defense. The Federal Civil Defense Administration has obtained such effects information, and additionally has trained its personnel in various test-conducted programs. In all of this broad field of study of the effects of atomic energy, it has been found that certain answers can only be obtained in the presence of a nuclear detonation. In this respect, the Nevada Test Site (and to some extent the Pacific — site) is used as an outdoors laboratory for non-military applications. While most field tests are therefore developmental in nature, the cost in material and effort is so great for any given test that every effort is made to answer with it as many other questions as possible. Summary of United States Nuclear Tests by Series The progressive frequency with which basic ideas have been generated and basic questions raised in weapons development and in effects is indicated by the schedule of detonations in Nevada and the Pacjfic. The scheduling and the number of series since 1950 should indicate also the rate at which questions have been raised and answered. Shot totals are those which have been publicly announced, Trinity Site, New Mexico, July 1945 (one) Bikini Atoll, mid-1946 (two) Eniwetok Proving Ground, spring 1948 (three) -3-