The study of officership is the study of leadership. Like all professions, the two-fold mission of the officer corps is to develop expert knowledge and to impart that knowledge to one’s successors. The debate about how to do this imparting resurfaces periodically throughout our nation’s history, and it is a hot topic today with the Army struggling to transform while facing massive mid-career officer shortages and fighting two counterinsurgencies. In studying the art of leadership, we would do well to recall one of the master mentors of the Army, Major General Fox Conner.To those who have heard of him, Fox Conner’s name is synonymous with mentorship. He is the “grey eminence” within the Army whose influence helped to shape the careers of George Patton, George Marshall and, most notably, President Dwight D. Eisenhower, but little is known about Conner himself. A careful study of his life with particular attention to his relationships with his three most famous protégés offers contemporary readers a highly salient example to emulate. Hailed by his peers, subordinates and superiors as a consummate master of the art of war, Conner was a respected practitioner of his craft for four decades. He had a gift for recognizing and recruiting talented protégés to work for him. He challenged each of them to develop his strengths and overcome his weaknesses, tailoring his own techniques to complement each individual’s personality—and he wasn’t afraid to break the rules to help them to advance professionally.This monograph examines Fox Conner’s life with particular attention to his career prior to World War I and his relationships with Patton, Marshall and Eisenhower. Today it is time for a new generation of leaders to learn from and follow Conner’s example, and train future members of the profession of arms to lead the Army in the 21st century