According to a Japanese survivor of the August 6, 1945, Hiroshima bombing, Agawa Hiroyuki, "the dead excluding soldiers were 59,000 to 64,000 in mid-December that year . . . 50 percent dying during the first six days, and 99 percent during the first forty days." Later estimates would put the total loss of life at 140,000. A second bomb was dropped on Nagasaki on August 9. The blast of the "Fat Man" plutonium bomb was almost twice the power of the Hiroshima bomb. Forty thousand people were instantly annihilated. The city was 90 percent destroyed. Faced with such devastation, Japan surrendered on August 10, ending World War II.

After the war, the Manhattan Project was officially terminated. Los Alamos continued its research and development of nuclear weapons, but both the military and peaceful use of nuclear energy was handed over to the civilian-controlled Atomic Energy Commission on January 1, 1947. During the years just after World War II, many scientists...