4-81. Units conduct defensive operations and designate FPFs for each of their supporting artillery units and mortar platoons. Both direct and indirect-fire weapons can provide FPFs. A direct fire weapon system’s final protective line is a form of FPFs. Commanders can only assign each weapon, firing battery, or platoon a single FPF. An FPF is a priority target for that weapon or unit, and those weapons or units are laid on that target when they are not engaged in other fire missions. When an enemy force initiates its final assault into a defensive position, a defending unit initiates its FPFs.