Charles Sweeney
Poor bombing visibility and an increasingly critical fuel shortage eventually forced "Bockscar" to divert from Kokura and attack the secondary target, Nagasaki. As they approached Nagasaki, the heart of the city's downtown was covered by dense cloud, and Sweeney and the plane's weaponeer, Commander Ashworth, initially decided to bomb Nagasaki using radar. However, a small opening in the clouds allowed "Bockscar's" bombardier to verify the target as Nagasaki. As the crew had been ordered to drop the bomb visually if possible, Sweeney decided to proceed with a visual bomb run. "Bockscar" then dropped "Fat Man", with a blast yield equivalent to 21 kilotons of TNT. It exploded 43 seconds later at above the ground, at least northwest of the planned aim point. The failure to drop "Fat Man" at the precise bomb aim point caused the atomic blast to be confined to the Urakami Valley. As a consequence, a major portion of the city was protected by the intervening hills, and only 60% of Nagasaki was destroyed. The bombing also severed the Mitsubishi arms production extensively and killed an estimated 35,000-40,000 people outright, including 23,200-28,200 Japanese industrial workers, 2,000 Korean slave laborers, and 150 Japanese soldiers.
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."