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Source : Richardrhodes.Com "RICHARD RHODES is the author or editor of twenty-four books including The Making of the Atomic Bomb, which won a Pulitzer Prize in Nonfiction, a National Book Award and a National Book Critics Circle Award"
In this book Mr. Rhodes documents interviews taken after the war. One of the interviews was with Japan's leading physicist who also headed up Japan's atomic bomb research program ( yes, Japan was working on the atomic bomb as were several other countries in the 1930's). He was called to Hiroshima to advise Japan on what to do. Seeing that the USA had used a uranium based bomb, this physicist advised his government to CONTINUE THE WAR, as it would take months to prep another uranium bomb. After Nagasaki, however, he found evidence of a plutonium based bomb and advised his government to SURRENDER or face total destruction. So you see, even the first bomb was not enough to end the war. And the rest, as they say, is history.