Association of 10 European countries to coordinate matters of European security and defense. The WEU was formed in 1955 as an outgrowth of the Brussels Treaty of 1948. Composed of Belgium, France, Germany, Greece, Italy, Luxembourg, The Netherlands, Portugal, Spain, and Britain, it works in cooperation with NATO and the European Union and is administered by a council of the foreign affairs and defense ministers of the member countries. There are also several associate members, observers, and associate partners. It is headquartered in Brussels