Japan hosts G7 leaders in Hiroshima this week hoping to drive home the dangers of nuclear weapons and push for progress on disarmament.
But with North Korea and Russia making nuclear threats, and China growing its arsenal, there may be little appetite for bold action on Prime Minister Fumio Kishida's stated goal of a "world free of nuclear weapons."
Here are some questions and answers about nuclear weapons and what Japan hopes to achieve:
Which G7 states are nuclear-armed?
Three G7 members -- the United States, Britain and France -- have nuclear arsenals, with Washington holding an estimated 5,244 warheads, according to the Federation of American Scientists (FAS).
The figure, which includes stockpiled, reserve and retired warheads, dwarves the inventories of France and Britain, estimated by FAS at 290 and 225 respectively.
Several G7 members, however, either host US nuclear weapons or are covered by the US "nuclear umbrella" -- an expectation that Washington would deploy the weapons in their defence if necessary -- including Japan.
What treaties cover nuclear weapons?
Perhaps the most famous treaty covering nuclear weapons remains the Nuclear Non-Proliferation Treaty (NPT), which opened for signature in 1968.\ A total of 191 states, including China, Russia, France, Britain and the United States are parties.
The core of the treaty is a pledge by nations not to acquire nuclear weapons if they do not have them, and for nuclear-armed countries to share peaceful technology while aiming to dismantle their arsenals.
