As Clausewitz observed, “In war more than anywhere else, things do not turn out as we expect.” The essence of war is a competitive reciprocal relationship with an adversary. Commanders and institutional leaders must recognize shortfalls and resolve gaps rapidly in the middle of the fog of war. The side that reacts best (and absorbs faster) increases its chances of winning. Mars Adapting examines what makes some military organizations better at this contest than others. It explores the institutional characteristics or attributes at play in learning quickly. Adaptation requires a dynamic process of acquiring knowledge, the utilization of that knowledge to alter a unit's skills, and the sharing of that learning to other units to integrate and institutionalize better operational practice. Mars Adapting explores the internal institutional factors that promote and enable military adaptation. It employs four cases, drawing upon one from each of the U.S. armed services. Each case was an