From the Document: "The Department of Defense (DOD) defines command and control (C2) as '[t]he exercise of authority and direction by a properly designated commander over assigned forces in the accomplishment of the mission.' At its most fundamental level, C2 represents how DOD makes operational decisions. One can view C2 through the context of five variables: who, what, when, where, and how. Traditionally, Congress has focused on the authorities (the 'who') and technology (the 'how') variables, and less so on the force mix ('what'), temporal ('when'), and geographic ('where'). China and Russia have developed strategies to disrupt or potentially deny DOD its ability to make decisions; as a result, DOD is modernizing systems and processes to command and control military forces."
CRS In Focus, IF11805
Congressional Research Service: https://crsreports.congress.gov/