How many countries have nuclear weapons and how many are there? How destructive are today’s nuclear weapons? What about “nuclear deterrence” theory? Do nuclear weapons help keep the peace? What is the Treaty on the Prohibition of Nuclear Weapons? Why does this treaty matter if none of the countries with nuclear weapons have joined? Why should one country give up its nuclear weapons if other countries still have them? Why should countries that don’t have nuclear weapons care about this treaty? Can a NATO state join the TPNW? Did Ukraine give up nuclear weapons?