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.
William Penney, Baron Penney
Along with RAF Group Captain Leonard Cheshire, he accompanied the American Team to Tinian Island from which the Hiroshima and Nagasaki missions were flown. On 9 August 1945 he witnessed the bombing of Nagasaki. The US authorities had controversially stopped them seeing the Hiroshima detonation, but at the last minute Penney and Cheshire were granted permission to fly in the B-29 "Big Stink", one of the observation planes that accompanied the Nagasaki weapon delivery bomber "Bockscar". Due to the belated permission, "Big Stink" missed its rendezvous with the bomber at Nagasaki. They saw the Nagasaki detonation from the air at a distance. As the leading expert on the effects of nuclear weapons, Penney was a member of the team of scientists and military analysts who entered Hiroshima and Nagasaki following the Japanese surrender on 15 August 1945 to assess the effects of nuclear weapons.