Map showing the five founding Member States of Western Union (WU). The Brussels Treaty establishing Western Union is signed on 17 March 1948 and enters into force on 25 August 1948.

Map showing the birth in 1955 of Western European Union (WEU), which succeeded Western Union. As part of the Paris Agreements, the Protocol modifying and completing the 1948 Brussels Treaty was signed in the French capital on 23 October 1954 and came into force on 6 May 1955.

Map showing accessions to Western Union (WU) and Western European Union (WEU) and the status of their members. Established in 1954, WEU is the heir to WU, which came into being in 1948 with the signing of the Brussels Treaty. Since 30 June 2011, the WEU as such ceased to exist.

Map showing the operations conducted by Western European Union (WEU) in Iraq and the Persian Gulf between 1987 and 1991 in the context of the Iran–Iraq War and the Gulf War.

Map showing the operations led by Western European Union (WEU) from 1992 to 2001 in connection with the crises and conflicts in the Balkans.