The foundation of effective multiple-casualty incident (MCI) management is the Incident Command System (ICS). NREMT teaches that ICS provides clear leadership, communication, accountability, and coordination of resources.

Option D is correct because ICS allows for scalable management, efficient delegation, and integration of multiple agencies.

Option B is important but is a component of ICS, not the core principle.

Option C is a tactical step that occurs within the command structure.

Option A misunderstands ICS, as command is established based on arrival, not rank alone.

NREMT stresses that without ICS, MCIs become chaotic and unsafe, regardless of clinical skill.