The Deputy Flag Officer-in-Command, or DFOIC is the second highest position of authority, or the second-in-command, of a major Starfleet field division such as a Federation fleet, next to the Flag Officer-in-Command.
Duties & Functions
The DFOIC's chief duty is to carry out the FOIC's orders. One of the DFOIC's chief responsibilities is the training, discipline and management of the entire field division's personnel. In that capacity, the DFOIC makes recommendations for promotions and transfers based from the rank of Commander upwards.
As the field division's second in command, the DFOIC will immediately assume command if anything renders the FOIC unfit for duty. The DFOIC is often the closest flag officer to the FOIC since to the two generally are the most senior flag officers in the division. As such, the DFOIC also often acts as the FOIC's conscience and confidante. The DFOIC is the highest ranking administrative officer in the division and frequently must act as liaison between task force commanders. Finally, the DFOIC is specifically tasked by Starfleet Command to determine when a FOIC oversteps his/her bounds.
In most cases, a DFOIC has the rank of Vice Admiral or Rear Admiral (upper grade), or in the case of Invincible-class-led task forces, by a Rear Admiral (lower grade). But on very rare occasions, flag officers with the rank of full Admiral are assigned as DFOIC's, for as long as the FOIC is a Fleet Admiral in rank.
In Starfleet's Vanguard Command, there are two Deputy Flag Officers-in-Command. Vice Admiral Anastassia Folonova is the DFOIC and the second-in-command of Fleet Admiral Maximus Hunter in all of Vanguard Command. On the other hand, Vice Admiral John Blackbull is the DFOIC of Hunter in the Vanguard Fleet. Folonova, therefore, has a higher position than Blackbull. Blackbull effectively serves as the third-in-command of the entire unit.