From a military operational standpoint, surprise is an event or capability that could affect the outcome of a mission or campaign for which preparations are not in place. By definition, it is not possible to truly anticipate surprise. It is only possible to prevent it (in the sense of minimizing the number of possible surprises by appropriate planning), to create systems that are resilient to an adversary's unexpected actions, or to rapidly and effectively respond when surprised. Responding to Capability Surprise examines the issues surrounding capability surprise, both operational and technical, facing the U.S. Navy, Marine Corps, and Coast Guard. This report selects a few surprises from across a continuum of surprises, from disruptive technologies, to intelligence-inferred capability developments, to operational deployments, and assesses what the Naval Forces are doing (and could do) about them while being mindful of future budgetary declines. The report then examines which processes are in place or could be in place in the Navy, the Marine Corps, and the Coast Guard to address such surprises. Today's U.S. naval forces continue to face a wide range of potential threats in the indefinite future and for this reason must continue to balance and meet their force structure needs. The recommendations of Responding to Capability Surprise will help to ensure more responsive, more resilient, and more adaptive behavior across the organization from the most senior leadership to the individual sailors, Marines, and Coast Guardsmen.