This volume presents the story of how ideas of the global cultivation of mathematics, across national borders, gradually began to take shape a century ago and how these ideas developed, amidst political difficulties and serious setbacks, into a fruitful worldwide cooperative effort under the aegis of the IMU. The author hopes that this history will improve understanding of the important role the Union has played in the promotion of mathematics throughout the world and that the record of past events might serve as a guide for the future.