After World War I, realizing the tragedy which was taking place in Europe, Coudenhove-Kalergi began a fight for the unity of Europe. His first book -in fact a manifesto- titled Pan-Europa was published in 1923, and each copy contained a membership form which invited the reader to become a member of Pan-Europa movement. Thus, Coudenhove-Kalergi was the founder of the first grassroots movement for European unity. The movement held its first Congress in Vienna in 1926. The following year Aristide Briand was elected as its honorary president.

"Europe as a political concept does not exist. This part of the world includes nations and states installed in the chaos, in a barrel of gunpowder of international conflicts, in a field of future conflicts. This is the European Question: the mutual hate of the Europeans that poisons the atmosphere. (....) The European Question will only be solved by means of the union of Europe's nations. (...) The biggest obstacle to the accomplishment of the United States of Europe is the one thousand years old rivalry between the two most populated nations of Pan-Europe: Germany and France..."

Richard Coudenhove-Kalergi, Pan-Europa, 1923.