Following the First World War, some thinkers and visionaries again began to float the idea of a politically unified Europe. In 1923, the Austrian Count Richard von Coudenhove-Kalergi founded the Pan-Europa Movement and hosted the First Paneuropean Congress, held in Vienna in 1926. The aim was for a Europe based on the principles of liberalism, Christianity and social responsibility. Before the communist revolution in Russia, Leon Trotsky foresaw a "Federated Republic of Europe — the United States of Europe", created by the proletariat.