This is from a Mason-Dixon Tavern article published by Gen
D.S. Walter, AoS and Commandant of the
I never could understand why the relevant optional rule is called “Manual Defensive Fire” instead of “Four Phase Format” or something like that. The present name is confusing for it sounds like MDF were the opposite of ADF, which it isn’t; one can play “Manual Defensive Fire” (Phases) with ADF (AI runs the defensive phase for the non-phasing player).
For all those, who like me, get easily confused, here’s the three possible settings:
MDF On plus ADF Off: Game plays in four phases per turn, file has to be returned to non-phasing player for his Defensive Fire Phase. Six file exchanges per turn*.
MDF On plus ADF On: Game plays in four phases per turn, the AI conducts the Defensive Fire Phase for the non-phasing player. Two file exchanges per turn.
MDF Off and ADF On or Off (no difference: Game plays in a single phase per turn, the AI conducts opportunity Defensive Fire for the non-phasing player. Two file exchanges per turn.
*(1st side movement phase/2nd side defensive fire phase/1st side offensive fire phase and melee/2nd side movement phase/1st side defensive fire phase/2nd side offensive fire phase and melee)