The Treaty on European Union, commonly known as the Maastricht Treaty, is the foundation treaty of the European Union (EU). Concluded in 1992 between the then-twelve member states of the European Communities, it announced "a new stage in the process of European integration" chiefly in provisions for a shared European citizenship, for the eventual introduction of a single currency, and (with less precision) for common foreign and security policies. Although these were widely seen to presage a "federal Europe", the focus of constitutional debate shifted to the later 2007 Treaty of Lisbon. In the wake of the Eurozone debt crisis unfolding from 2009, the most enduring reference to the Maastricht Treaty has been to the rules of compliance – the "Maastricht criteria" – for the currency union.