A study of General Walton H. Walker's career offers a lens through which to view the evolution of Army training doctrine, revealing its strengths and weaknesses over a period of nearly four decades. However, an understanding of the skills necessary to train units for combat cannot consist solely of a review of training doctrine. General Walker's career provides valuable insights into the real-world challenges a leader experienced training an Army unit, both in war and in peacetime. The resource constraints, political realities, and physical hardships that make Army training so difficult to accomplish with skill and foresight cannot be gleaned from classroom lectures or the pages of a journal or doctrinal publication. Further, an analysis of the breakout and pursuit Walker's XX Corps executed in Normandy, and later the performance of the Eighth Army during the first weeks of combat in Korea, reveal how General Walker applied contemporary training principles to develop combat formations that performed exceptionally well in combat. Finally, a review of current training principles demonstrates that Walker emphasized the same principles throughout his career that retain primacy in today's Army. This reveals Walker's lasting legacy: in addition to performing among the best of the Army's commanders in combat, Walker set himself apart as one of the leading trainers in U.S. Army history.