text: Command and Support Relationships
  up the organizational integrity of the force for separate employment. Under OPCON forces assigned may
  only be employed within certain constraints such as function, time, or location imposed by the higher echelon
  authority.
  Tactical Command
  B-49. TACOM in NATO is the authority delegated to a commander to assign tasks to forces under that
  command for the accomplishment of the mission assigned by higher authority. Under TACOM the gaining
  commander may only allocate to the assigned force a specific task consistent for the accomplishment of the
  mission and purpose assigned by the higher commander. Under TACOM the assigned force is allocated for
  specific tasks, and it is normally allocated for a limited period. This prevents the gaining commander from
  employing the assigned force in a role or manner not intended by the higher commander. When the task is
  complete or the specific timeframe expires, the TACOM relationship with the gaining force ends.
  Tactical Control in NATO
  B-50. TACON in NATO is the detailed and usually local direction and control of movements or maneuvers
  necessary to accomplish missions or assigned tasks. TACON is generally used to indicate those units that
  will be located in another unit or formation’s assigned geographic boundaries, where the gaining unit
  becomes responsible for coordination aspects within the shared AO. The gaining commander has authority
  to coordinate local defense, including force protection and terrain allocation.