Nine sovereign states are generally understood to possess nuclear weapons,
though only eight formally acknowledge possessing them. In order of
acquisition of nuclear weapons, these are the United States, Russia (as
successor to the former Soviet Union), the United Kingdom, France, China,
Israel (not formally acknowledged), India, Pakistan, and North Korea.
The first five of these are the nuclear-weapon states (NWS) as defined by
the Nuclear Non-Proliferation Treaty (NPT). They are also the permanent
members of the United Nations Security Council and the only nations confirmed
to possess thermonuclear weapons. Israel, India, and Pakistan never joined the
NPT, while North Korea acceded in 1983 but announced its withdrawal in 2003.