Western Union (alliance) followed by Western European Union
The Western Union (WU), also referred to as the Brussels Treaty Organisation (BTO), was the European military alliance established between France, the United Kingdom (UK) and the three Benelux countries in September 1948 in order to implement the Treaty of Brussels signed in March the same year. Under this treaty the signatories, referred to as the five powers, agreed to collaborate in the defence field  as well as in the political, economic and cultural fields.
During the Korean War (1950–1953), the headquarters, personnel and plans of the WU's defence arm, the Western Union Defence Organisation (WUDO), were transferred to the newly established North Atlantic Treaty Organization (NATO), providing the nucleus of the European half of NATO's command structure (Allied Command Europe), led by Supreme Headquarters Allied Powers Europe (SHAPE). As a consequence of the failure of the European Defence Community in 1954, the London and Paris Conferences led to the Modified Treaty of Brussels (MTB) through which the Western Union was transformed into the Western European Union (WEU) and was joined by Italy and West Germany. As the WEU's functions were transferred to the European Union's (EU) European Security and Defence Policy (ESDP) at the turn of the 21st century, the Western Union is a precursor of both NATO and the military arm of the EU.Transformation into the Western European Union
The Western Union's founding Treaty of Brussels was amended at the 1954 Paris Conference as a result of the failure of the Treaty establishing the European Defence Community (EDC) to gain French ratification: The General Treaty (German: Deutschlandvertrag) of 1952 formally named the EDC as a prerequisite to the end of Allied occupation of Germany, and there was a desire to include Germany in the Western defence architecture. The Modified Brussels Treaty (MBT) transformed the Western Union into the Western European Union (WEU), at which point Italy and Germany were admitted. Although the WEU established by the MBT was significantly less powerful and ambitious than the original Western Union, German membership in the WEU was considered sufficient for the occupation of the country to end in accordance with the General Treaty.Social and cultural aspects were handed to the Council of Europe to avoid duplication of responsibilities within Europe.Since the end of World War II, sovereign European countries have entered into treaties and thereby co-operated and harmonised policies (or pooled sovereignty) in an increasing number of areas, in the European integration project or the construction of Europe (French: la construction européenne). The following timeline outlines the legal inception of the European Union (EU)—the principal framework for this unification. The EU inherited many of its present responsibilities from the European Communities (EC), which were founded in the 1950s in the spirit of the Schuman Declaration.