Although not EU treaties per se, these treaties affected the development of the EU defence arm, a main part of the CFSP. The Franco-British alliance established by the Dunkirk Treaty was de facto superseded by WU. The CFSP pillar was bolstered by some of the security structures that had been established within the remit of the 1955 Modified Brussels Treaty (MBT). The Brussels Treaty was terminated in 2011, consequently dissolving the WEU, as the mutual defence clause that the Lisbon Treaty provided for EU was considered to render the WEU superfluous. The EU thus de facto superseded the WEU.
