Which of the following classes of fire is NOT needed to fire a final protective line (FPL)?

The concept of a final protective line (FPL) is crucial in defensive operations, where it acts as a predetermined line of fire that units utilize to create an effective barrier against enemy advances. To properly establish and employ an FPL, understanding the types of fire used is essential.

Indirect fire is not used for an FPL because an FPL is designed for immediate, direct engagement with an enemy that is within the effective range of the weapon systems. Indirect fire, on the other hand, involves firing at targets that are out of the line of sight of the weapon, typically using trajectory-based firing techniques. Since the purpose of an FPL is rapid response to an enemy threat with direct fire, relying on indirect fire does not fulfill this tactical requirement.

In contrast, searching fire, enfilade fire, and grazing fire each serve vital roles in establishing an FPL. Searching fire allows for a wide area of coverage to be engaged, enfilade fire takes advantage of positional advantages by firing along the length of enemy formations, and grazing fire ensures engagement at lower trajectories, which is particularly effective in flat terrain. Each of these types of fire contributes to the effectiveness and lethality of an FPL, making indirect fire unnecessary in this context.