The Department of Defense’s National Disaster Medical System (NDMS) Pilot Program sponsored the National Emergency Medical Services (EMS) Capability and Capacity Study to examine whether the nation’s current EMS enterprise has the capability and capacity to provide EMS services in support of a nationwide NDMS activation during a large scale combat operation (LSCO). Specifically, the study considered the Pilot’s scenario of 1,000 wounded Service members arriving in the continental United States (CONUS) per day for 100 days. These Service members would arrive at one of 64 Federal Coordinating Centers (FCC) and require transport to the receiving definitive care facilities (i.e., Department of Defense medical treatment facilities, Department of Veterans Affairs medical centers, or private-sector hospitals in the NDMS network). Many members of the community of interest have likened the demand for EMS services in this scenario to that of interfacility transport, as patients would receive medical care and be stabilized prior to transport to the FCC. To deconstruct this complex problem, the study team developed an operational concept graphic and an operational activity decomposition tree to describe the scope of the study. Input from the community of interest was obtained through interviews and a data collection tool to identify capability and capacity gaps. The study team aligned these gaps against the sub-capabilities in the operational activity decomposition tree and consolidated statements so that each gap was only represented once. Findings from this study will help inform the Pilot and key stakeholders across the NDMS on the limitations of a national EMS response to a LSCO-driven NDMS activation.