Final protective fire
From Halopedia, the Halo wiki
Final protective fire, abbreviated as FPF, and also known as danger close, refers to a tactical plan for a military unit, typically infantry, to protect itself in defense against attack. The plan generally includes machine gun, mortar, and artillery fire prearranged to impede enemy movement across defensive lines or areas.
As the "final" in the name implies, it is the last resort in defensive plans, normally involving artillery and/or heavy machine gun fire directed dangerously close to friendly defensive positions that are at risk of being overrun by the enemy. A request for final protective fire generally has absolute priority over any other kind of requests. More or less often, "danger close" salvos are typically initiated within 100 or less meters of a friendly defensive position, making them dangerous to anything within the nearby radius.
In 2552, during the evacuation of New Alexandria, the UNSC Army enacted two phases of final protective fire to protect the New Alexandria Starport from attack by a Covenant corvette bearing down on the city. However, the measures were unsuccessful in stopping the ship, and at least one of the fleeing evacuation transports was destroyed by the corvette.
In 2559, Jerome-092 called in a danger close Archer missile bombardment from the UNSC Spirit of Fire to cover Red Team's escape from Banished forces at the Henry Lamb Research Facility on Installation 00. The escape was successful, with the Spartans successfully recovering the AI Isabel and extracting Douglas-042 for medical attention.
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