The collection and use of lessons is neither a new phenomenon nor a new need. What is new is the quantity and velocity of current and historical lessons available to commanders and soldiers in almost real-time. Despite these recent advances, there is no indication that we have reached a plateau in our ability to collect and share lessons. The authors argue for the centrality of Lessons Learned structures and techniques for accelerating learning, knowledge and adaptation in complex operations both for civilian and military organizations. Focusing on the military environment and touching on recent civilian lessons learned efforts, the authors conduct an historical review of structures and techniques, highlighting the on-going “learning competition.”