Since the publication of the first edition of Head Strong in 2014, developments in military psychology have been rapid and important-so much so that this revised edition is necessary to accurately capture the vital role that psychology continues to play in twenty-first-century military success. The ideas contained in the first edition influenced emerging doctrine in the Army's Human Dimension and informed military leaders around the globe of ways that psychological science and practice may be leveraged to improve combat effectiveness. Many of the predictions made in the first edition have come true, and new and exciting products of military psychology now offer novel ways of impacting military outcomes. This revised edition of Head Strong updates the 13 chapters included in the first edition with breaking news in military psychology and adds new material to augment those chapters.