scientists. Nonetheless, by 1944 sufficient progress had been made to persuade the scientists that their efforts might succeed. A test of the plutonium implosion device was necessary to determine if it would work and what its effects would be. Led by Dr. J. Robert Oppenheimer, Manhattan Project scientists at Los Alamos Laboratory (later to become the Los Alamos National Laboratory) were "to make preparations for a field test in which blast, earth shock, neutron and gamma radiation would be studied and complete photographic records made of the explosion and any atmospheric phenomena connected with the explosion" (1: 13,14). The planned firing date for the TRINITY device was originally 4 July 1945. On 14 June 1945, Dr. Oppenheimer changed the test date to no earlier than 13 July and no later than 23 July. On 30 June, the earliest firing date was moved to 16 July, even though better weather was forecast for 18 and 19 July. The TRINITY test organization adjusted the schedule because the Allied conference in Potsdam, Germany, was about to begin and the President needed the results of the test as soon as possible (1: 26). ‘ On 6 August 1945, 3 weeks after the detonation of TRINITY, the first uranium-fueled nuclear bomb, a gun-type weapon code named LITTLE BOY, was detonated over Hiroshima. On 9 August, FAT MAN, a plutonium-fueled implosion weapon with the same design as the TRINITY device, was detonated over another Japanese city, Nagasaki. Two days later, the Japanese Government informed the United States of its decision to surrender. On 2 September 1945, Japan officially surrendered to the Allied Governments, thereby bringing World War II to an end (1: 11). 4.1.2 TRINITY Test Operations. From 16 July 1945 through 1946, about 1,000 military and civilian personnel took part in Project TRINITY or visited the test site. All participants, civilian as well as military, were under the authority of the MED. Project activities included scientific studies. Military exercises were not conducted at TRINITY (1: 1). The Los Alamos Laboratory, which was staffed and administered by the University of California (under contract to the MED), conducted diagnostic 71