August 6 and 9 - Atomic bombings of Hiroshima and Nagasaki make the world aware of the power of nuclear weapons.
August 21 - American physicist Harry Daghlian accidentally drops a tungsten carbide brick onto a plutonium-gallium alloy bomb core, exposing himself to a lethal dose of neutron radiation and becoming the first known fatality due to a criticality accident 25 days later.