There are currently five states that are known to have have successfully detonated nuclear weapons. These five are considered to be "nuclear-weapon states" (NWS) under the terms of the Theatre Nuclear Weapons Treaty (TNWT). In order of acquisition of nuclear weapons these are: the British Empire, the Union of American People's Republics, the Dominion of Canada, the Fifth French Republic, the Republic of China, and the People's Republic of China. Nations that are known or believed to possess nuclear weapons are sometimes referred to as the nuclear club. The Soviet Union is also widely believed to have nuclear weapons, though it has refused to confirm or deny this, and is not known definitively to have conducted a nuclear test.