Secretary of War Henry Stimson rules out Kyoto, the ancient capital of Japan, as a target for atomic attack.

464 B-29s raid Tokyo again, burning out nearly 16 square miles of the remaining city. Only a few thousand are killed, urban inhabitants have learned to flee fire bomb attacks quickly and escape the flames. Also, Operation OLYMPIC, the invasion of Kyushu (the southern Japanese island), is set for November 1.

Target Committee reconvenes. On the committee now are J. Robert Oppenheimer, John von Neumann, Deak Parsons, and Hans Bethe. Meeting discusses issues combat employment of atomic bombs (e.g. proper burst height, etc.). Target list is shortened to Kyoto, Hiroshima, Yokohama, and Kokura Arsenal (Niigata is considered).

The 100-ton test is conducted. 108 tons of TNT, laced with 1000 curies of reactor fission products, are exploded 800 yards from Trinity ground zero to test instrumentation for The Trinity Test. This is the largest instrumented explosion conducted up to this date. Also, Nazi Germany surrenders to the Allies.

Initiator Committee (Hans Bethe, Enrico Fermi and Robert Christy) selects the most promising design for fission initiator (neutron generator) to be used in the implosion bomb. The "Urchin" design is favored, and work on initiator fabrication begins. Also, first batch of supplies for the atomic bomb deployment leaves for Tinian Island from Wendover, Utah.