Pakistan also is not a party to the Nuclear Non-Proliferation Treaty. Pakistan covertly developed nuclear weapons over decades, beginning in the late 1970s. Pakistan first delved into nuclear power after the establishment of its first nuclear power plant near Karachi with equipment and materials supplied mainly by western nations in the early 1970s.
The country is currently thought to have had a stockpile of around 240 warheads, though because of the limited information available, estimates range from 100 to 400. China is the only NPT nuclear-weapon state to give an unqualified negative security assurance with its "no first use" policy.
France tested its first nuclear weapon in 1960 ("Gerboise Bleue"), based mostly on its own research. It was motivated by the Suez Crisis diplomatic tension vis-à-vis both the Soviet Union and the Free World allies United States and United Kingdom.
Five are considered to be nuclear-weapon States (NWS) under the terms of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). In order of acquisition of nuclear weapons these are: the United States, Russia (the successor state to the Soviet Union), the United Kingdom, France, and China.
North Korea was a party to the Nuclear Non-Proliferation Treaty, but announced a withdrawal on January 10, 2003, after the United States accused it of having a secret uranium enrichment program and cut off energy assistance under the 1994 Agreed Framework.