The Fifth Man (5th Man) is the fifth arriving law enforcement officer. The first four arriving officers typically form the initial Contact Team(s) and enter, so the fifth officer stays outside, at a chosen location close to the affected building, to establish command. Rank does not matter: the fifth arriving officer assumes the role regardless of whether they are a patrol officer or a supervisor.
The Fifth Man fills the Tactical Group Supervisor position. For the full description of that role, including its responsibilities for security and movement in the Hot and Warm Zones, see Tactical Group Supervisor.