An excerpt from The Basic ICS for Initial Response ICS200

An Incident Command, Section, or Branch may have one or more Deputy Incident Commanders. ICS only requires that a Deputy be fully qualified and equally capable of assuming the position. To designate a Deputy Incident Commander is for three primary reasons: to perform specific tasks as requested by the Incident Commander and to perform incident command functions in a relief capacity, like taking over for the next operational period. The Deputy will assume the primary role and represent an assisting agency that might share jurisdiction or gain jurisdiction in the future.

Activation of the Command Staff depends on the needs of the incident, and it will only be activated if a command position is needed. A Liaison Officer may not be required if there are no outside agencies or organizations to coordinate with. The Command Staff comprises a public information officer, a liaison officer, and a safety officer.