In May of 2018, 7,000 personnel from 162 organizations representing the militaries of the United States and nine NATO partners converged on five training sites in southern Germany as part of the U.S. Army’s first Joint Warfighting Assessment (JWA). The common goal was to advance their collective ability to overcome aggression from a near-peer competitor in Europe. In pursuit of this goal, they trained to fight as a single, cohesive, and multinational division against a near-peer adversary. This training produced numerous lessons, many of which are detailed throughout this publication, about how to foster interoperability and about which concepts and capabilities will enable multi-domain operations (MDO). JWA 18 was an important step forward for the Army as it seeks to adapt the force to the demands of a rapidly changing and complex world.