query: Which countries are known to have nuclear weapons?
passage: List of states with nuclear weapons
There are eight sovereign states that have successfully detonated nuclear weapons.[1] 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.
passage: Nuclear sharing
In peacetime, the nuclear weapons stored in non-nuclear countries are guarded by United States Air Force (USAF) personnel and previously, some nuclear artillery and missile systems were guarded by United States Army (USA) personnel; the Permissive Action Link codes required for arming them remain under American control. In case of war, the weapons are to be mounted on the participating countries' warplanes. The weapons are under custody and control of USAF Munitions Support Squadrons co-located on NATO main operating bases who work together with the host nation forces.
, 180 tactical B61 nuclear bombs of the 480 U.S. nuclear weapons believed to be deployed in Europe fall under the nuclear sharing arrangement. The weapons are stored within a vault in hardened aircraft shelters, using the USAF WS3 Weapon Storage and Security System. The delivery warplanes used are F-16s and Panavia Tornados.
Historically, the shared nuclear weapon delivery systems were not restricted to bombs. Greece used Nike-Hercules Missiles as well as A-7 Corsair II attack aircraft. Canada had Bomarc nuclear-armed anti-aircraft missiles, Honest John surface-to-surface missiles and the AIR-2 Genie nuclear-armed air-to-air rocket, as well as tactical nuclear bombs for the CF-104 fighter. PGM-19 Jupiter medium range ballistic missiles were shared with Italian air force units and Turkish units with U.S. dual key systems to enable the warheads. PGM-17 Thor intermediate range ballistic missiles were forward deployed to the UK with RAF crews. An extended version of nuclear sharing, the NATO Multilateral Force was a plan to equip NATO surface ships of the member states with UGM-27 Polaris missiles, but the UK ended up purchasing the Polaris missiles and using its own warheads, and the plan to equip NATO surface ships was abandoned.
After the Soviet Union collapsed, the nuclear weapon types shared within NATO were reduced to tactical nuclear bombs deployed by Dual-Capable Aircraft (DCA). According to the press, Eastern European Member States of NATO have resisted the withdrawal of the shared nuclear bombs from Europe, fearing it would show a weakening of U.S. commitment to defend Europe against Russia.