Since the 1950s, European integration has seen the development of a supranational system of governance, as its institutions move further from the concept of simple intergovernmentalism and more towards a federalised system. However, with the Maastricht Treaty of 1992, new intergovernmental elements have been introduced alongside the more federal systems, making it more difficult to define the European Union (the EU). The European Union, which operates through a hybrid system of intergovernmentalism and supranationalism, is not officially a federation – though various academic observers regard it as having the characteristics of a federal system.
A Pan-European movement gained some momentum from the 1920s with the creation of the Paneuropean Union, based on Richard von Coudenhove-Kalergi's 1923 manifesto Paneuropa, which presented the idea of a unified European State. This movement, led by Coudenhove-Kalergi and subsequently by Otto von Habsburg, is the oldest European unification movement. His ideas influenced Aristide Briand, who gave a speech in favour of a European Union in the League of Nations on 8 September 1929, and in 1930, who wrote his "Memorandum on the Organization of a Regime of European Federal Union" for the Government of France.
We must build a kind of United States of Europe. In this way only, will hundreds of millions of toilers be able to regain the simple joys and hopes which make life worth living.
At the end of World War II, the political climate favoured unity in Western Europe, seen by many as an escape from the extreme forms of nationalism which had devastated the continent. In a speech delivered on 9 September 1946 at the University of Zurich, Switzerland, Winston Churchill postulated a United States of Europe.