In 1929 Aristide Briand gave a speech in the presence of the League of Nations Assembly in which he proposed the idea of a federation of European nations based on solidarity and in the pursuit of economic prosperity and political and social co-operation. In 1930, at the League's request, Briand presented a Memorandum on the organisation of a system of European Federal Union. The next year the future French prime minister Édouard Herriot published his book The United States of Europe.