The United Kingdom has possessed weapons of mass destruction, including nuclear, biological, and chemical weapons. The United Kingdom is one of the five official nuclear weapon states under the Nuclear Non-Proliferation Treaty and has an independent nuclear deterrent. The U.K. has been estimated to have a stockpile of approximately 160 active nuclear warheads and 225 nuclear warheads in total. The United Kingdom renounced the use of chemical and biological weapons in 1956 and subsequently destroyed its general stocks.