The threat of nuclear war is expected to feature highly on the agenda when leaders meet for the G7 summit in Japan this weekend.
The gathering will take place in Hiroshima, the site of the first atomic attack in 1945 and which has since become a symbol of global peace.
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”.
How many countries have nuclear weapons?
As it stands, there are nine countries that possess nuclear weapons: Russia, the US, Britain, France, India, Pakistan, China, North Korea and Israel.
Several other Nato countries – including Turkey, Germany, Belgium, the Netherlands and Italy – allow US warheads to be stationed on their soil.
Observers have warned that the proliferation of nuclear weapons is growing, not easing, amid an increasingly unstable geopolitical climate.
The US Department of Defence said in a report last year that China's nuclear warhead supply has surpassed 400 and it is on a path for about 1,500 warheads by 2035.
Iran has been accused of attempting to enrich uranium to advance its own clandestine nuclear weapons programme, but the prospect of a nuclear-armed Tehran remains years away.
How many nuclear warheads are there?
Most of the thousands of nuclear weapons in the world are in the nuclear arsenals of the US and Russia.
Nuclear-armed states have 12,700 nuclear warheads, of which 9,400 are in active military stockpiles.
This is far fewer than the estimated 70,000 during the height of the Cold War.
However, nuclear arsenals are expected to grow over the coming decade and today’s weapons are vastly more capable than those used against Japan in the Second World War.
What nuclear treaties exist?
North Korea fires missiles towards the Sea of Japan
Perhaps the most famous treaty covering nuclear weapons is the Nuclear Non-Proliferation Treaty, which opened for signatures in 1968.
A total of 191 states, including China, Russia, France, Britain and the US, are parties to the treaty.
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.
In July 2017, the Treaty on the Prohibition of Nuclear Weapons was adopted by more than 100 UN states.
Campaigners view the more recent pact as filling the NPT's “gaps” by demanding the elimination of nuclear weapons.
No nuclear power has signed it and it is actively opposed by some.
France and the US last year called it “at odds with the existing non-proliferation and disarmament architecture”.
Japan is not party to the TPNW.
