A second group of states has derivative association with nuclear artillery. These nations fielded artillery units trained and equipped to use nuclear weapons, but did not control the devices themselves. Instead, the devices were held by embedded custodial units of the developing countries. These custodial units retained control of the nuclear weapons until they were released for use in a crisis. This second group has included such North Atlantic Treaty Organisation (NATO) countries as Belgium, Canada, West Germany, Greece, Italy, the Netherlands, Turkey, and the United Kingdom.