One hundred years ago, the US Army suddenly found itself at the center of one of the greatest human conflicts until that time. World War I came at a time when the Army lost the institutional knowledge of how to raise and employ large armies in the decades after the Civil War. Our Army needed to transform itself in short order into a world-class fighting organization, capable of engaging one of the world’s best armies. At the same time, it needed to adapt to modern weapons and technologies. Dr. Leo Hirrel has prepared a comprehensive study of the emergence of Army sustainment as a key part of transforming itself into a modern fighting force. It is a story of how the Army began with only the vaguest notions of how to support a multi-million Soldier Army, and with even less concept of how to operate overseas. Yet by the end of the war, the Army developed sustainment solutions that would last through the next war and beyond. Of course there were numerous mistakes and miscalculations, but the achievements were truly remarkable. This is a story for all students of military history. Understanding the role and development of sustainment functions in the American Expeditionary Forces is critical to appreciating the Army in World War I. This book provides a breadth of education for military leaders regardless of their branch.