Military officers attending the Center for Creative Leadership's (CCL ®) Leadership at the Peak program participated in a survey of their key developmental experiences and the lessons learned from those events. The research indicated that events involving Positive Role Models, Negative Role Models, and Failures and Mistakes were the most frequently reported development experiences, and produced lessons on Managing Subordinates, Executive Leadership, Communication, Integrity, and Decision Making. Understanding the types of events that lead to these vital lessons can provide current and future officers a greater ability to guide subordinates with opportunities to learn, plus identify situations that can deliver important leadership lessons. These key events also assist practitioners when creating tools and processes to enhance leadership development.