During the interwar period, the consciousness that national markets in Europe were interdependent though confrontational, along with the observation of a larger and growing US market on the other side of the ocean, nourished the urge for the economic integration of the continent. In 1920, advocating the creation of a European economic union, British economist John Maynard Keynes wrote that "a Free Trade Union should be established . . . to impose no protectionist tariffs whatever against the produce of other members of the Union. " During the same decade, Richard von Coudenhove-Kalergi, one of the first to imagine of a modern political union of Europe, founded the Pan-Europa Movement. His ideas influenced his contemporaries, among which then Prime Minister of France Aristide Briand. In 1929, the latter gave a speech in favour of a European Union before the assembly of the League of Nations, precursor of the United Nations. In a radio address in March 1943, with war still raging, Britain's leader Sir Winston Churchill spoke warmly of "restoring the true greatness of Europe" once victory had been achieved, and mused on the post-war creation of a "Council of Europe" which would bring the European nations together to build peace.
The EU was not always as big as it is today. When European countries started to cooperate economically in 1951, only Belgium, Germany, France, Italy, Luxembourg and the Netherlands participated.