Introduction: In the event of a large-scale combat operation (LSCO), combat casualties will receive significant care in field-forward environments due to contested air space and the tyranny of distance. The forward deployment of health and medical units will remove Active Duty personnel from military treatment facilities (MTFs) and Reserve Components and National Guard Bureau personnel, leaving Veterans Administration medical centers (VAMCs) and civilian hospitals understaffed. Future LSCOs are anticipated to return a substantial volume of combat casualties to the United States, which will require definitive care in MTFs, VAMCs, and civilian hospital settings. However, the simultaneous deployment of Reserve and Guard units will deplete facilities of staff in an environment in which hospitals are operating at capacity, jeopardizing the continuity of care for both civilians and combat casualties. Materials/Methods: Leadership from the National Center for Disaster Medicine and Public Health, the Deputy Assistant Secretary for Homeland Defense Integration and Defense Support for Civil Authorities, the Medical Readiness Division within the National Guard Bureau, and the civilian health sector will serve as moderators and panelists to facilitate the discussion. This panel will briefly introduce the simultaneity challenge and discuss implications from the health and medical perspective with a focus on force mobilization. Results: The discussion will focus on the cascading impacts across military and civilian healthcare following the deployment of health and medical units. Specifically, the simultaneous challenge of mobilizing forces abroad and domestically creates potential risks to homeland security and domestic incident management.