Atomic bombings of Hiroshima and Nagasaki
By August 1945, the Allies' Manhattan Project had produced two types of atomic bombs, and the 509th Composite Group of the United States Army Air Forces (USAAF) was equipped with the specialized Silverplate version of the Boeing B-29 Superfortress that could deliver them from Tinian in the Mariana Islands. Orders for atomic bombs to be used on four Japanese cities were issued on July 25. On August 6, one of the modified B-29s dropped a uranium gun-type bomb codenamed "Little Boy" on Hiroshima. Three days later, on August 9, a plutonium implosion-type bomb codenamed "Fat Man" was dropped by another B-29 on Nagasaki. The bombs immediately devastated their targets. Over the next two to four months, the acute effects of the atomic bombings killed 90,000–146,000 people in Hiroshima and 39,000–80,000 people in Nagasaki; roughly half of the deaths in each city occurred on the first day. Large numbers of people continued to die from the effects of burns, radiation sickness, and other injuries, compounded by illness and malnutrition, for many months afterward. In both cities, most of the dead were civilians, although Hiroshima had a sizable military garrison.
Stafford L. Warren
The detonation of the two atomic bombs in Japan "raised as many military and medicomilitary questions as they answered". A series of nuclear tests was planned, codenamed Operation Crossroads. Some 42,000 personnel were deployed to Bikini Atoll as part of Admiral William H. P. Blandy's Joint Task Force 1 to conduct the test. Their health and safety was Lyons's responsibility, but the specialised job of radiological safety was handled by the Manhattan Project. Warren, as Chief of the Radiological Safety Section (RADSAFE), planned and implemented measures to assess, limit and control the impact of radiation. Teams were given special training at Oak Ridge in the operation of instrumentation to measure radioactivity, and the interpretation of their readings. Training was also conducted aboard en route to Bikini Atoll, where it arrived on 12 June 1946. In all, some 3,500 personnel were assigned to RADSAFE. Warren was appalled by the effects of radioactive contamination on the environment. "The deadly range of radioactive products from the atomic bomb has been clearly demonstrated under controlled conditions..." he wrote, "the only defense against atomic bombs still lies outside the scope of science. It is the prevention of atomic war."