For major commands, you're talking about the order of battle at the theater, regional, or Operational level. Higher, and you're talking National Defense Strategy (all services) or National Military Strategy (ground forces). Within a given theater of operations, you have tactical units (Divisions on down) to accomplish local objectives that support relevant parts of the national strategy, such as a Theater Engagement Plan.
That last helps to make sure that all the players in an area know each other. Sometimes it really helps to literally know who to call to sort things out.