August 6

On August 6, 1945, a nuclear bomb was detonated in Hiroshima. It was the first time a nuclear weapon had been used offensively.

Hiroshima had been targeted partly because it was a military center that had suffered little damage during the war and the number of rivers running through it made it a bad candidate for incendiary bombs.

As post-war US continued creating new and more effective bombs, the Soviet Union caught up in the arms race. The first nuclear treaty, the Partial Test Ban Treaty, was ratified by the US Senate in 1963. The difference between a treaty and an executive agreement is that the Senate ratifies a treaty. The effect on US law is the same, which is to say it becomes part of US law in accordance with the Constitution.

The Partial Test Ban Treaty in 1963 forbid all nuclear testing that was not underground. China, France and North Korea are the only known countries with known capability that have not signed the treaty.

This was followed by the Nuclear Non-Proliferation Treaty in 1968, also ratified by the US Senate. India, Israel, Pakistan and North Korea are not parties. North Korea had been, but withdrew in 2003.

This treaty allows development of nuclear power, but does not allow the development or manufacture of nuclear weapons.

As of 2009, the US has signed the Comprehensive Nuclear Test Ban Treaty, but not yet ratified it. This treaty would ban all nuclear testing, and create norms that would force non-signatories to comply with other nuclear treaties.

The damage done in Hiroshima and Nagasaki was considerable. It is estimated 30% of Hiroshima's population died on detonation. Deaths from radiation-caused cancers continued for decades. Japan does not have a nuclear weapons program and does not intend to.