Get the latest tech news

The Third Atomic Bomb

After the atomic bombings of Hiroshima and Nagasaki, the US Army Air Force had plans to drop a third bomb on August 19, 1945—with more to come if necessary. Fat Man bomb casing at the USAF Museum

That caused a debate in Washington, with one faction rejecting the offer and holding out for Potsdam’s strict terms of “unconditional surrender”, and the other arguing that having the Emperor remain in office under American authority would make the giant task of controlling the defeated Japanese population much easier. Ironically, the argument and delay over the Emperor’s status also proved to be unnecessary: the US kept Hirohito as the head of government (subject to the American occupation forces under General Douglas MacArthur), just as the Japanese had been insisting, in order to maintain control over the islands, to keep stability among the defeated population, and, most important, to groom Japan as a US ally in the upcoming Cold War. On August 21, 1945, less than a week after Japan notified the US that it would accept the terms of the Potsdam Declaration, physicist Harry Daghlian was performing an experiment when he accidentally dropped a piece of “tamper” material, used to reflect neutrons back into the core, and triggered a critical mass.

Get the Android app