GREENHOUSE advances. MIKE, an experimental device, produced the first thermonuclear detonation, which means that a substantial portion of its energy was generated by the fusion, or joining, of hydrogen and other light atoms. KING was a stockpile weapon, modified to produce a large yield. The energy from KING was generated by the fission, or splitting, of plutonium atoms (10: 1). The IVY test program was the result not only of scientific and technical considerations, but also of an intense controversy within elements of the U.S. Government concerned with foreign policy and defense matters. During the early 1950s, various plans rapidly evolved to meet the challenge posed by the initial Soviet detonation, of 1949. Most plans called for increased development and production of fission weapons and the required delivery systems. One plan called for the development of fusion, or thermonuclear, weapons with vastly greater explosive power. Opponents of fusion weapons argued that the Soviets could be persuaded not to develop these weapons if the United States would refrain. A further argument, among others, was that such weapons were not much more effective than high-yield fission weapons (10: 18). The advocates of fusion weapons prevailed, and MIKE became the centerpiece of Operation IVY and the proof-test of the new technology. KING, however, represented a test of the kind of high-yield fission weapon some of the fusion opponents had in mind. To a degree, the KING device also offered a backup to help ease the national sense of vulnerability in the event that the initial attempt at a fusion reaction detonation was unsuccessful (10: 18-19). 4.8.2 IVY Test Operations. IVY engaged nearly 11,650 participants, of whom approximately 9,350 were military and about 2,300 were civilians. Most of the civilians and over 6,600 of the military personnel operated from Enewetak Atoll and from task force ships based there. These personnel were removed to evacuation ships before the detonation of MIKE. Most of the additional military were Air Force personnel who were based at Kwajalein, 350 nautical miles southeast of Enewetak (10: 2,178-181). 96