Il faut dépenser au moins 1 MF plein pour ouvrir le droit à un tir défensif.
A9.2 ... a DEFENDER MG cannot fire at the same unit in the same Location more times than the number of MF/MP expended by the target inthat Location (FRD, but a minimum of once per hex)
3.3.3. Defensive fire: Any time a unit or stack expends MF or MP in the LOS of a Good Order DEFENDER unit, the DEFENDER has the option to temporarily halt movement while he fires at it in that location with as many attacks as he can bring to bear.