The August 1945 Hiroshima and Nagasaki atomic bombings killed tens of thousands of people outright and drew a line in history between the prenuclear world and what came afterward.
Japan remains the only country subjected to a nuclear attack and the United States the only nation to ever use these weapons of mass destruction.
A decade into the 21st century, the world may now be trying to back away from atomic arms and proliferation — a movement initiated by U.S. President Barack Obama's vision for "a world without nuclear weapons."